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This is the current revision of this page, as edited by Lowercase sigmabot III (talk | contribs) at 01:30, 7 June 2021 (Archiving 2 discussion(s) from Talk:Most recent common ancestor) (bot). The present address (URL) is a permanent link to this version.

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Archive 1

MRCA and LCA compared

Due to an inquiry in Last Common Ancestor I took a shot clearing up the confusion, maybe this will help.

An LCA is in fact the individual (or founding group) at the bifurcation point between two species. For us, this individual, which lived between two million and 40,000 bce, and no others contributed ALL of the genes that make up humanity. If we could pin the date down more closely we could probably call it "The MRCA between modern man and XXX" but we don't know the XXX.

Now fast forward to 2007. You and I and every person on earth could trace our ancestries back to around 2,000 years ago and find a common grandparent, aka The MRCA of All Mankind. Unlike the LCA, the genetic contribution of this ancestor to any one person is extremely small. This is because some ten million of his contemporaries ultimately get into the action.

Obviously the MRCA of All Mankind cannot be both of these individuals. Chang, et al, call the individual of 2,000 years ago the MRCA of All Mankind. So we call the other guy, the individual that began the species, the LCA (of all mankind).

Tom Schmal 06:19, 6 November 2007 (UTC)

You have posted the exact same comment here and in the talk page of LCA. Can we please keep all discussions on the same page please. Let's discuss it at Talk:Last Common Ancestor#Confusing article to avoid further confusion. You will find my original comment on that page, and new stuff I am about to post now. Fred Hsu 23:15, 6 November 2007 (UTC)

Patrilineal and matrilineal ancestry

This section states "The MRCA of humans alive today necessarily lived more recently than either." This is incorrect. If we imagine that there are four living humans, two males and two females, with matrilineal ancestor 3 generations back, with the males having the same father, then the "most recent common patrilineal ancestor of all living male humans" is more recent than the MRCA of all humans. Even if we use a definition of y chromosome Adam that includes the patrilineal ancestor of living females, this is still only exactly as recently, not more recently.

I'd suggest changing this to "The MRCA of humans alive today likely lived much more recently than either. By definition, the MT-MRCA is a common ancestor, but not likely the most recent. The Y-MRCA is by definition only the common ancestor of all males, but still likely to be much deeper in the past than the unrestricted MRCA, who may be an ancestor on any line."

But I don't have a citation for this. Can someone verify that the cite given for the original actually says this? I think someone may have simplified it, but using "necessarily" could be confusing.Kevinpet 06:12, 21 August 2007 (UTC)

MRCA is calculated based on statistical analysis of gene data. It assumes the current population size of humans. That is, we are not talking about 2 males and 2 females. We are talking about billions of poeple. Statistically speaking, unqualified MRCA must be more recent than the other two. Fred Hsu 14:23, 21 August 2007 (UTC)
Yep. The probability that the MRCA is the same as the matrilinial or patrilineal MRCA is not technically zero, but is vanishingly small. The same applies to molecules of gas. The probability of all the oxygen molecules happening to leave your area of the room, suffocating you, is not zero. But in practice, it never happens. Rracecarr 19:12, 21 August 2007 (UTC)

From vfd

from VfD:

Keep. Nunh-huh's fix makes the page work for me. I am replacing the VfD with a "stub" to save everybody's time. If you think otherwise, then please replace the VfD notice on the Most recent common ancestor page and post your objections above. Thanks. ---Rednblu 20:22, 2 Oct 2004 (UTC)

Nonsense page currently. Possibly a valid topic combining general principles from both Mitochondrial Eve and Y-chromosomal Adam. New page by a new citizen, but this page may be part of a prank--see questions on bottom of Talk:Mitochondrial Eve. ---Rednblu 19:15, 2 Oct 2004 (UTC)
  • keep. This is a well known topic in genetics, and it's distinct from "Mitochondrial Eve" and "Y-chromosomal Adam": the MRCA of present-day humanity is considerably more recent than either "Eve" or "Adam" - Nunh-huh 19:22, 2 Oct 2004 (UTC)
  • Keep. I don't see why the current page is nonsense. It's a bit stubby. See also Genealogy (section The "Maximum Relationship"), which contains material that can put here (after it is corrected). Eugene van der Pijll 19:22, 2 Oct 2004 (UTC)
  • Keep. Valid topic, well-written. RickK 19:40, Oct 2, 2004 (UTC)
  • Keep. Notable concept, good article. — Gwalla | Talk 21:34, 2 Oct 2004 (UTC)
  • Keep Looks like a good topic and article to me... --Asmodai 15:47, Oct 3, 2004 (UTC)

end moved discussion

MRCA should be renamed to MRPA

I believe the confusion about this term is to do with how a single individual can pass on his or her DNA to all living individuals. The Most Recent Common Ancestor is a misnomer for the Most Recent Prolific Ancestor. Shared DNA merely means a single ancestral tree among a forest of ancestral trees has passed DNA on to all living individuals via prolific production of progeny who spread out through all the DNA trees of all living individuals. It is not indicative of a single source but merely a indicator of a single common point of some source DNA among many sources of DNA. IF you were to talk about multiple points of infection and view this shared DNA as if it were a virus you would realize it is just one virus among many but that it has infected everyone through time. It can then be viewed as an indicator of a very mobile population group who shared a common ancestral root and who seeded their DNA into many DNA trees throughout all know population groups. So the MRCA aka MRPA becomes an indicator of the most recent spread of a single source of DNA among all groups.

—The preceding unsigned comment was added by 210.209.65.40 (talk) 09:25, 5 April 2007 (UTC).

Wikipedia is not a place for original research. If you can find published papers calling concestors MRPAs, then please update the article. Otherwise, we need to stick to names used in the scientific community. Besides, what you described was MRCA via a particular gene path (such as mt-mrca or Y-mrca). When unqualified, MRCA refers to the common ancestor reached via either parent. Fred Hsu 02:55, 6 April 2007 (UTC)

Two meanings?

I believe that the MRCA is purely a mathematical model which accounts for mutation rates, migration, etc, but has nothing whatever to do with individuals taking genealogical DNA tests. If I'm correct then the second paragraph of this article should be revised.

One alternative might be the insertion of a new paragraph to distinguish between meanings. Here's a stab at it:

The term is used in two ways. In ordinary usage the most recent common ancestor refers to:

  • An individual identified as the most recent ancestor of two persons -- by DNA testing of two males or two females, or by traditional genealogy.

In scholarly usage, however, it has another meaning:.

  • An individual who lived at a time which has been estimated by a mathematical model accounting for the rate of mutation (and sometimes also the rates of migration, inbreeding, etc.) and who is the most recent ancestor of all males, all females, or all living persons.

Any comments, objections, etc.? AnonUser 14:49, 14 October 2005 (UTC)

The article, by focusing on the phrase "the MRCA of X", is better as is. You seem to be confusing "the MRCA of X" with "an estimate of when the MRCA of X lived". What does need emphasizing is that the MRCA of humans alive today may not have been the same individual as the MRCA of humans alive when (say) The Descent of Man and Selection in Relation to Sex was first published. Also some clarification about things like whether both parents of two siblings are regarded as the MRCA, or whether it is the younger of the two.Peak 16:38, 14 October 2005 (UTC)

I agree with the focus as is. The article is confusing, however, because it uses multiple definitions of MRCA. I propose that the article clearly distinguish among them up front. AnonUser 19:24, 14 October 2005 (UTC)

The article gives a definition in the very first sentence, and uses it consistently. I don't see a second definition, either explicitly or implicitly. Which sentence do you think is the source of confusion? Peak 22:08, 14 October 2005 (UTC)

Ah so -- you are correct. Perhaps its confusing because the examples are so dissimilar, without language tieing them together. If its confusing to me, its probably confusing to other readers too. Maybe a little tweaking would help. AnonUser 02:57, 15 October 2005 (UTC)

Time estimates

Long discussion here. My issue is that on one hand we are saying the MRCA may have lived in the common era, on the other hand we are saying MRCA lived in paleolithic, defined in that article as 2.5 MYA to 10 KYA. This is not helpful at all, we need a tighter bound. Since we know from the y-chromosomal Adam article that he lived just 60 KYA, can we at least deduce that MRCA was more recent than that? This would place MRCA between 60 KYA and 1000 CE. If no counter-comments I will update. Skates61 (talk) 23:29, 27 June 2008 (UTC)

Ok, rwr8189 was correct in reverting my blank out of this section- the cited articles are in Nature and have subsequently been cited by others, and after reading them they certainly make a case worthy of discussion. However, I feel there two corrections should be considered: 1. in the '04 article they use the admittedly naive system in which any two humans can randomly breed in any given generation (this yields the 1000 CE date). This simplification should be explicitly stated as a model, or the very-recent daate should be dropped in lieu of the same group's more advanced and recent estimate (the 2005 nature paper). 2. Make the point that for a given non-isolated population, the MRCA is surprisingly recent, but also that the existence of even a single isolated population or insufficiently mixed population implies a much earlier MRCA (though still not the tens of thousands of years I had expected.) coments? Jodine Sparks 20:20, 3 July 2007 (UTC)


This section is based on a single study amongst a fairly large field of research, and the results of said study are patently false. Until someone can rewrite it with actual 'time estimates' that correspond to a older MRCA than 1000AD (which is obvious), I just going to comment it out. I hope this is not too presumptuous, but this section as it stands is only presenting known misinformation. Jodine Sparks 16:45, 29 January 2007 (UTC)


To: EamonnPKeane. Kindly state all your assumptions, including:

  • the number of years between generations;
  • the percentage of couples who were childless;
  • the percentage of children who died before puberty; and
  • the percentage of relatives (however distant) who married each other. AnonUser 03:47, 29 November 2005 (UTC)

The "historical times" estimate is patently ridiculous, imho; it seems they used some sort of diffusion to model human migration. The statement

The actual MRCA is farther back if one attempts to take into account long-isolated peoples, such as historical tribes in central Africa, Australia and remote islands in the South Pacific.

betrays the preceding estimate: We defined the MRCA as that of all humans alive today, so what do you mean "if one attempts to take into account tribes in Central Africa"? Unless you want to argue they are not human, you'll have no choice but to take them into account. I can easily believe the MRCA of Europeans (or even continental Eurasians) lived in the Common Era. It is inconceivable that the MRCA of all humans lived after 3000 BC: A single isolated tribe (Pygmies, Aboriginals, Indonesian bushmen, take your pick) pushes the MRCA back to the Paleolithic. I can easily imagine, even, that the MRCA of 99% of humans alive today lived in historical times, but it takes just a single surviving individual from an isolated lineage to render that calculation obsolete. dab (ᛏ) 09:56, 3 January 2006 (UTC)

I think that the suggestion of a human MRCA having lived from between 3000BC to 1000AD(!) is absolutely ridiculous. What kind of pseudo-science must this be? Think about it, if it were true, there would for example be no single 100% pure-blooded Native American alive today (since the Native Americans had reached and spread throughout the American continents well before 3000BC, a possible exception to this being the Eskimos) which, be they few, I think there are.

I agree that this is ludicrous. Are we talking about all humans or aren't we? Ancestors of Aborigines are believed to have arrived in Australia between 40k and 50k years ago: http://en.wikipedia.org/wiki/Indigenous_Australians I have a hard time believing that I, a white man, have a common ancestor with a black aborigine as recently as 4000 years ago. Who wrote this crap? Additionally, that time estimate 3000BC to 1000AD suspiciously encompasses when the Christian or Hebrew "creation" would have taken place. Zmbe 06:02, 11 March 2006 (UTC)

Now it does not: see Jewish calendar#Epoch or Ussher-Lightfoot Calendar#Ussher.27s history of the Earth, both of which suggest a date earlier than 3000 BC. --Henrygb 19:46, 11 March 2006 (UTC)
bad math on my part- however, i see from the ussher-lightfoot calendar that the time estimate DOES encompass the time of the 'great flood,' which may deserve suspicion. Zmbe 07:18, 12 March 2006 (UTC)

The whole concept of a purely mathematical MRCA is both unscientific and useless. It assumes the nonsensical notion that one's ancestors double with each generation backward, so that, for example, 20 generations ago I had a million (2^20) ancestors, or almost that many. But the human genome contains no more than 25,000 genes! In other words, no matter how many generations back I go, I cannot have any more than 25,000 genuine ancestors--i.e., ancestors who have actually contributed to my genome. All the other thousands or millions are ancestors on paper only, and have no scientific or practical significance.

Let's now even consider those 25,000 distant ancestors. Each contributed as little as a single gene to my genome. Big deal! Such an ancestor still has no practical significance to those living today, unless perchance that ancestor contributed a crucial improvement to humanity that we now all share. But I know of no such great improvement in the human genome within the last 70,000 years.

The bottom line here is that, beyond 20 generations, the ONLY ancestors that are of practical significance to humans living today are the two ancestors who contributed a SIGNIFICANT quantity of genetic material: the Y-chromosome ancestor and the mitochondrial DNA ancestor. Thus, it is for good reason that those interested in distant genealogy (beyond 20 generations) focus on the strict patrilineal and matrilineal lines.

i don't think the idea is that every person has one gene per ancestor. you might want to check your source on that one. anyway, please add your id and timestamp to all entries- it's easy to do by typing four tilda's ~ in a row after your entry.Zmbe 06:31, 3 August 2006 (UTC)
Well, arguably you don't know that your inherited Y-chromosome DNA (if you're male) and your mitochondrial DNA exceed the contribution of other genes. Other genes are subject to recombination, sure, but since the ancestral populations were incredibly small in some cases, most of our recombining DNA could be from a very small group of people. --Saforrest 06:25, 29 November 2006 (UTC)


"The whole concept of a purely mathematical MRCA is both unscientific and useless. It assumes the nonsensical notion that one's ancestors double with each generation backward, so that, for example, 20 generations ago I had a million (2^20) ancestors, or almost that many. But the human genome contains no more than 25,000 genes! In other words, no matter how many generations back I go, I cannot have any more than 25,000 genuine ancestors--i.e., ancestors who have actually contributed to my genome. All the other thousands or millions are ancestors on paper only, and have no scientific or practical significance."

Good point, except that on top of what you mentioned, there is an extremely high degree of redundancy amongst those 2^20 ancestors. In other words, not only do some ancestors contribute zero genes to you (as you pointed out), but also, a given ancestor from 20 generations back is most likely your ancestor many, many times over (so, due to the redundancy factor, the number of actual ancestors at a given number of generations back is way less than the mathematical value).

"The bottom line here is that, beyond 20 generations, the ONLY ancestors that are of practical significance to humans living today are the two ancestors who contributed a SIGNIFICANT quantity of genetic material: the Y-chromosome ancestor and the mitochondrial DNA ancestor. Thus, it is for good reason that those interested in distant genealogy (beyond 20 generations) focus on the strict patrilineal and matrilineal lines."

Here you are absolutely wrong. Mitochondrial DNA does not code for anything except mitochondria, and the y-chromosome (in males only) is far from the only chromosome that codes for traits. It is true that for a large number of generations ago, only some of an individual's ancestors of that generation contributed to his/her genetic makeup. However, it is NOT the case that these individuals are restricted to the direct maternal and paternal lines. Some of the genes that make me distinct could have come to me via my mother's father's father's mother's father's mother's mother's .... It is incorrect to say that one's genes come strictly from the direct male and direct female lines (else, why do some people clearly take after a mother's father or a father's mother?!?)


—Preceding unsigned comment added by 151.207.242.4 (talk) 02:18, 24 October 2007 (UTC)

MRCA of different species

I've added a section on MRCA of different species, and referenced Richard Dawkins' book, The Ancestor's Tale. I recommend it, especially to those who have contributed to the discussion above. He places a lower-bound of 13,000 years on the age of the MRCA of all humanity (with a rather sad proviso – see later). This is because it is known that the native population of Tasmania was physically separated from the rest of the world 13,000 years ago, and therefore we could not share a later ancestor with them. The only problem is that the Europeans who colonised Tasmania treated them as vermin and exterminated the whole lot by 1876. Also, FWIW, Dawkins reckons on an upper limit of 100,000 years as the age of the MRCA of all of us. --Portnadler 17:23, 8 May 2006 (UTC)

As I recall from the book, the point was that they exterminated all the "pure-blooded" ones. Presumably there are a few descendants still alive (as there are of the Beothuks, a similar sad story), but of course people of such recent mixed heritage would not preserve the 13,000-year genetic separation necessary to retain the MRCA figure. --Saforrest 06:03, 29 November 2006 (UTC)

Descendents of Edward IV and Henry VII

What sort of social rank would one have to bear in their family, in order to be a descendent of either?

How far up the totem pole, would you say?

This is intended to have broad answers and based on gradients of time and population, not going into specifics about exact descendents. About how common is their descent in the English or British genepool today?

I've noticed that American Presidents don't descend from either king, but the most common recent royal ancestor shared by many of us is Edward III. How common is it for anybody in the English or British genepool, to have a Protestant royal ancestor?

There is a general cutoff, isn't there?

Is it because of fratricide in the Wars of the Roses, the Tudors' "new men", or the Union of the Crowns, or the parliamentary union under Queen Anne (I can't think of any non-royal family descent from the Hanoverians within the UK)?

I'm thinking that there is a big difference between Plantagenet and Tudor descents, that the commons in all likelihood have the former and the latter is held by the lords. (just generally speaking) Then again, Tudor descent in the Welsh must be higher in general. I am further curious about pre-Royal Tudor blood in Anglo-British people today, since the status and/or concept of Welsh royalty/nobility is rather hazy in my mind. I found the Blevins aka Ap Bleddyn family of Powys in my ancestry, but have no real idea on what to make of it--or any other Welsh "native aristocracy". I might be able to find Stewart descent somewhere, from way back when. What percentage of Hanoverian background do you think that German colonists had in America?

On the British side, I have to go as far back as Welf himself...but any recent genetic relationship with the Hanoverians or the counts of Nassau are completely obscure. How does one research those other colonial people, such as the Hessians?

UK genealogy is relatively easy when focusing on English (and French) ancestries. What would a "national person" of Jerusalem (or Antioch, for example) in Crusader times be known as?

We say "American" for those Founders, but was there such a nationality-term for the Crusaders in their own domains?

I guess the term is supposed to be Levantine/Outremer, or "Crusader" as our national heritage says "Colonist"...

IP Address 11:48, 9 May 2006 (UTC)


I have a question:

After reading the article I was happy to see how closely related we are. I would really appreciate it if someone has more detailed information on population. I just can't get past the fact that the article seems to focus on 6.5 billion people. Our ancestors came and went throughout history. From the point of our MRCA's existance to present more than 6.5 billion people have lived. The town where I lived has an approximate population of 100,000 but from the day the founder came and died to present I can't even fathom how many people have lived here. Can someone help me find the numbers I need to understand?

Approximate total of humans since time of our MRCA:???

83.219.199.121 00:38, 23 July 2006 (UTC)Leif

I know this is a very late reply, but for the benefit of anyone else who should happen to read through this page I would like to point out that due to exponential population growth, the majority (or at least a very significant proportion) of humans who have ever lived are still alive today. Some towns may have had many more past residents than present ones, but on the other hand many towns were founded very recently and thus have few past residents. Robin S 03:03, 13 June 2007 (UTC)

If anyone doesnt have a significant other because they have come to terms with the fact that we are all related let me put this into your heads. I am almost positive that somewhere out there in the universe that there is another species that are exactly like us, humonoid, but do not come from a genetic line that comes from this planet. It is an infinite universe. The distance between them (a mating partner not of our gentic line) and us is trillions of light years away.--RCJACOBS100 23:55, 16 September 2006 (UTC)Robert Curley Jacobs

If I understand you correctly, you're saying it's okay to breed with "relatives" because there must exist copies of them on this faraway planet to whom you are unrelated. First off, no, it's not at all clear that it's an infinite universe. Second, even if such a doppleganger species did exist, what does that matter, since we are probably millions of years apart? Anybody you could conceivably want to breed with is still related to you.
Lastly, if one uses this "infinite universe" argument in the manner you've described, one could just as easily argue that there must exist a person who's identical to your mother or father. Therefore, incest is justified since an "unrelated copy" exists.
Sorry if that came across as excessively harsh. It's an interesting thought experiment. --Saforrest 06:00, 29 November 2006 (UTC)

Double meaning

"This simple calculation does not take into account the fact that every marriage is really a marriage between distant cousins which include second cousins, fourth cousins, sixteenth cousins and so on. The ancestry tree is not really a tree, but a graph. One can place all living people at the bottom of the graph and ancestors above their descendants. As each generation of ancestor is added at the top of the graph, there will eventually be an MRCA from whom it is possible to trace a path of direct descendants all the way down to every living person at the bottom of the graph."

I thought this was meant to describe a graph? It clearly descibes a tree to me: "...there will eventually be an MRCA from whom it is possible to trace a path of direct descendants all the way down to every living person at the bottom..." - THAT is a tree. (by 90.242.58.236 on 06:44, February 19, 2007)

I modified this paragraph to make it more clear. The MRCA was only one of many top-level, contemporary ancestors. The MRCA is not the only 'node' at the top of a 'tree'. The MRCA is one of many top-level 'nodes' of a 'graph'. Notice that the subsequent paragraph makes this even more clear; it describes how contemporaries of the MRCA also pass down their genes onto descendents. Fred Hsu 16:09, 19 February 2007 (UTC)

Generations

User:Robin S added the following which I just removed:

Indeed, within twenty generations, most descendants of an individual will not have inherited any of their genes from a given ancestor since there will be far more ancestors than genes. Since considerably more than twenty generations have passed since the hypothesized date of the human MRCA, it is possible that not a single human gene present today was inherited from that individual.

It is not immediately clear that in 20 generations the number of ancestors will be greater than number of genes. Please see the other paragraphs in the same session where 'tree' vs. 'graph' was discussed. Note that many ancestors are shared. Also see the chapter 'All Africa and her progenies' in River out of Eden. But perhaps you are right. We just need to find a reference which shows this to be true, taking into account the graph nature of human ancestry. Fred Hsu 17:48, 21 March 2007 (UTC)

I had a feeling someone would bring that up. It is true that exponential growth fails as a model if taken indefinitely since, as mentioned, over 80 generations one would expect over a trillion trillion ancestors. However, expecting the number of ancestors over 20 generations to be of a significantly lower order of magnitude than the 27 000 (<215) or so genes in the human genome seems to me to be unreasonable. For a start, wouldn't inbreeding pose a significant problem? Robin S 18:33, 21 March 2007 (UTC)

In page 60-61 of The Ancestor's Tale, Dawkins states that he believes that the almost identical ABO blood types in humans and chimps are examples of trans-specific polymorphism. That is, a type-B human may actually be more closely related to type-B chimp than type-B human is related to type-B human, from the perspective of the genes (or alleles) responsible for the antigens.

I wanted to add this to the article to indicate that by tracing ancestry based on other genes, we may actually reach startling conclusions about our most recent common ancestor. That is, I may share a type-B MRCA with an ape, while a type-B person shares another type-B MRCA with another ape.

But after some basic research on this topic, I found that Dawkins was probably wrong on this account. First, chimps don't have blood-type B. They only have A and O. Other primates have combinations of A, B, AB and O, with the exception of macaques which has all of them. This does not necessarily indicate the B-type in human is the same as B-type in apes, for instance. It could be that there was an original type-A inherited by all apes, including human. From there other blood-types developed. And it so happened that type-B and type-O are stable variants which appeared independently in different species.

Most of the studies on blood types across apes I could read online (without paying for subscriptions) were rather old (decades-old). The two recent ones I could read did not support Dawkins' view:

Evolution of Primate ABO Blood Group Genes and Their Homologous Genes1, Mol. Biol. Evol. 14(4):399411. 1997

Comparison of allele O sequences of the human and non-human primate ABO system. (Abstract-only), Immunogenetics. 1999 Jun;49(6):517-26.

Perhaps I need to get this book?

Can someone shed more light on this topic? Fred Hsu 23:33, 1 June 2007 (UTC)

First, genetics dictate that the following combinations of phenotypes are possible in a species: A and O or B and O or AB, A, B and O (this assumes that IA, IB and IO are the only possible alleles). However, beyond that there is no reason to suppose that all IB alleles (for instance) in different species are homologous. As I understand it, IB alleles arose as a point mutation in IA alleles, while IO alleles arose as a frame-shift mutation. There is no reason why such mutations could not occur multiple times in evolutionary history, even within the history of a single species. On the other hand, the fact that an IB allele is present in two different species does not indicate that the two incidences of the allele are not homologous. If chimps lack an IB allele in their populations, that could mean that it evolved independently in humans and other primates, or that it went extinct in chimps and the remainder of primates (though the latter seems less likely). Robin S 02:55, 13 June 2007 (UTC)
Right. This is consistent with what I found during my short research. So, I guess you are saying that I can't use this as a definite example of trans-specific polymorphism in the article, because we don't yet know the answer. Sigh. Fred Hsu 01:06, 14 June 2007 (UTC)
Ah, discussion on RichardDawkins.net generated more data points. Here is another paper:
Gene Diversity of Chimpanzee ABO Blood Group Genes Elucidated from Intron 6 Sequences
The paper doesn't specifically talk about trans-specific polymorphism. It is about estimates of nucleotide diversities in chimps and bonobos. But the chart on the second page seems to indicate that human ABO alleles are quite far apart from other apes in terms of nucleotide differences in intron 6 sequences. Fred Hsu 02:55, 9 November 2007 (UTC)

Nominated most ancient common ancestor for deletion

Someone created a new article called Most ancient common ancestor. Notice that it is ancient, not recent. It appears to be a new name coined by the author without research backing (i.e. original research). I nominated that page for deletion. Please visit Wikipedia:Articles for deletion/Most ancient common ancestor if you wish to participate in the discussion. Again, please note that I am not nominating the Most Recent Common Ancestor article for deletion; I am nominating the newly created Most Ancient Common Ancestor. Fred Hsu 05:41, 21 July 2007 (UTC)

people for some reason seem to have a lot of difficulty coming to terms with the concept, even if great pains are taken to explain it. I just noted flawed material at Last Common Ancestor, an article that should probably be merged here. dab (𒁳) 11:16, 23 July 2007 (UTC)

Why do you want o merge Last Common Ancestor into this article? They are clearly differently as you pointed out. And you split Identical ancestors point which I fully support. Why not create a new section in this article to talk about Last Common Ancestor, the same way it now talks about Identical Ancestors Point? Fred Hsu 21:55, 23 July 2007 (UTC)
Also note that Dawkins uses the term concestor to indicate the MRCA of a set of species in order to avoid confusing people. Perhaps this is what Last Common Ancestor attempts to describe... Search for concestor in this article. Fred Hsu 22:08, 23 July 2007 (UTC)
I just enhanced MRCA article to clarify relationship among MRCA, LCA and concestor. If there isn't a lot of extra material for LCA, then perhaps we can merge it into MRCA as you suggested. If we decide to leave them as separate articles, then we should probably redirect concestor to LCA instead of MRCA. Fred Hsu 03:44, 24 July 2007 (UTC)

Gene ancestry: question about tree vs. graph

Since an organism can have a copy of a gene from each parent, and these parents can share a common ancestor, does this mean that genes have ancestor and progeny graphs rather than trees? Or are two copies of a gene in a single organism not considered to be a single vertex in a gene ancestor/progeny diagram? Wikimedes (talk) 06:54, 18 November 2007 (UTC)

Please check out the first chapter 'Digital River' and (especially) the second chapter 'All Africa and her Progenies' of the article River out of Eden. These answer your question specifically. The short answer is: there are two types of ancestry chain/tree/graph you can draw. You can draw one from an organism's perspective, and you can draw another one from gene's perspective. The organism ancestry and pedigree are graphs. Genes have a single chain of ancestors and a tree of descendants. Fred Hsu (talk) 14:09, 18 November 2007 (UTC)

Changes by Lklundin on MRCA being a set of people

Lklundin introduced two sets of changes to the article. The first set of changes is about MRCA being a set of people as opposed to a single individual. I understand the reason behind these changes. While these changes seem rational, it is not how MRCA is typically described. Since the MRCA is not a real person, but is statistically computed, traditionally we use a single person to represent this idea. If we are going to suddenly define MRCA as a set of people, then we should start to call it 'most recent common ancestors' with an 's' at the end. We should also rewrite the whole article to be consistent with this change. We should also refer to African Eves, not the African Eve, as two sisters might have had identical mtDNA and together covered all living people on Earth today.

I am going to change the first paragraph back to the way it was, ok? Fred Hsu (talk) 00:22, 26 November 2007 (UTC)

Thank for the changes on calculation, by the way. It makes the paragraph better. Fred Hsu (talk) 00:33, 26 November 2007 (UTC)

Thanks for the constructive comments on my changes. At first I intended to make only some language changes, and then as an afterthought I realized that the MRCA need not be unique (it is obvious when one thinks about it, e.g. the mate/spouse of a MRCA is a likely 2nd MRCA, even though there can easily be many others). Since this was additionally my first edit on this article, I can understand why the change was not accepted in its entirety, and I think it would have been better to open this issue up for discussion first. Now that a discussion has been opened I would like to make a few points based on (the abstract of) J.T.Changs well-cited article: "Recent common ancestors of all present-day individuals":
1) While each of the patrilineal and the matrilineal MRCA is unique, the both-parent MRCA need not be unique.
2) "most recent" is defined in terms of generations, not years.
3) For a given population of size n, the number of generations, Tn, back to a MRCA has a distribution that is concentrated around log2(n), where log2 is the base 2 logarithm. In contrast, the expected number of generations back to one of the patrilineal and the matrilineal MRCAs is 2n (with a standard deviation of n).
4) Further: with high probability for large n, in each generation at least X log2(n) generations before the present, where X is some positive constant, all individuals who have any descendants among the present-day individuals are actually ancestors of all present-day individuals.
My opinion about my above points:
The article could be improved by clearly stating some non-statistical properties of the MRCA, i.e. that
A) 'most recent' is in terms of generations,
B) MRCA need not be unique
C) each individual in the population that coexisted with the MRCA(s) falls into one of three groups:
C1) Those who have no living descendents, and the remaining:
C2) ancestors of a subset of the current population, and
C3) people who are also ancestors of the entire current population, which would include any parents and grand-parents of the MRCA(s).
- and I think it is worth mentioning the following statistical property of the MRCA(s):
the age (in terms of generations) of the MRCA depends on the logarithm of the population size (which explains why the MRCA is estimated to have lived so much more recent than each of the patrilineal and matrilineal MRCA).
Finally, I also think it is worth mentioning that by going a certain number of generations further back, from that point and back the probability that group C2) is empty is high.
Lklundin (talk) 22:02, 28 November 2007 (UTC)
Great ideas and data. Perhaps a new section is needed for these. The concept of MRCA and its implications are complicated enough that many people already find it hard to understand. I believe we should try not to make existing sections more complicated than they already are, in an attempt to put forth all available information. A separate section to elaborate on points you raised here, perhaps after 2.4 Time estimates, will be more useful. Fred Hsu (talk) 00:45, 29 November 2007 (UTC)
By the way, are you familiar with "last common ancestor"? Can you comment on the issues I raised on Talk:Last_Common_Ancestor? Can you check out sections, 2, 3, 4 and 5 please? The original article before I pruned it can be found here. Thanks. Fred Hsu (talk) 00:45, 29 November 2007 (UTC)

notable coancestors

A section of notable coancestors, whould be really good both theoretical (roundish flatworm, Ohno's Cambrian pananimalia genomes, urcrustacean) and fossil (Wiwaxia, Hallucigenia, archaeopterix etc...)--Squidonius (talk) 17:26, 12 December 2007 (UTC)

You mean, something like the complete table of all concestors in the The Ancestor's Tale? Fred Hsu (talk) 23:04, 12 December 2007 (UTC)
I just just made this change to the article. Fred Hsu (talk) 23:09, 12 December 2007 (UTC)

I am deeply confused by this

Can we have something added in layman's terms? There is no real reference to what the subject matter is about and it doesn't explain clearly what the MRCA is actually for, it just jumps straight into jargon. JayKeaton (talk) 15:36, 8 August 2008 (UTC)

Hardly anything is "jargon" in the lead. This is not the Simple English Wikipedia here. The "layman" should know what the words descended, pedigree, DNA, mutation, and genealogy mean. Otherwise, there is nothing remotely confusing about the lead section. "The most recent common ancestor (MRCA) of any set of organisms is the most recent individual from which all organisms in the group are directly descended. The term is most frequently used as applying to humans." seems perfectly understandable to a reader to me.--Michael WhiteT·C 00:48, 9 August 2008 (UTC)
And everything you just said related to what? If someone was referred to this article from a 3rd party source would they know what it all means? Would they know what field it relates to or why MRCA as a science/term even exists? JayKeaton (talk) 12:55, 9 August 2008 (UTC)
Sorry, Jay, I'm not confused either and I think the opening sentence is just fine. I am not a fan of the next sentence on linguistics tho, I think it is too prominently placed and am thinking about moving it somewhere else within the article. If you are truly confused, the MRCAs of two first cousins is their grandparents.Skates61 (talk) 23:45, 17 September 2008 (UTC)

Family Tree DNA - Understanding MRCA - A good link?

There is certainly good information here, but it could be quite confusing, because at FT-DNA, they are computing time to direct paternal MRCA for two persons who have kit results. This is not the same as the MRCA on any route, which is the focus of this article. FT-DNA does not explain the distinction. Keep the link? Qualify it? Remove it? What's everyone's thoughts on this? —Preceding unsigned comment added by Skates61 (talk • contribs) 23:36, 17 September 2008 (UTC)

I agree with you, if you mean this link [1]. Having that external link will only confuse people. What they are doing is matching some select markers and applying statistical analysis to find best categorization. This is not what MRCA is really about. When we talk about MRCA via one single path, two descendants may have completely different DNA composition except this one gene. When we talk about MRCA of all humankind statistically, because of sexual recombination, some descendants may in fact have not one single gene in common with the MRCA. I am removing that link. Fred Hsu (talk) 03:15, 6 June 2009 (UTC)

"Mostly-acyclic"

From the article: "The ancestry tree is thus not strictly a tree, but a directed, mostly-acyclic graph." Am I missing something here? Barring any sort of a time-travel accident, I don't see how cycles are possible. 70.68.114.213 (talk) 19:15, 22 March 2009 (UTC)

Inbreeding is what you fortunately missed. Lklundin (talk) 22:24, 14 April 2009 (UTC)
The term directed, mostly-acyclic graph seems to suggest that a cycle in such a graph would be directed. However, the article on cycle graph states that a directed cycle graph is a cycle graph, with all the edges being oriented in the same direction. Although inbreeding can introduce a cycle into the graph, such a cycle cannot be directed, rather it consists of two different, directed paths from one person to another. So I agree that the term directed, mostly-acyclic graph can be confusing. Lklundin (talk) 11:13, 15 April 2009 (UTC)
In fact, the article on a directed acyclic graph is exactly the type of graph that one or more cases of pedigree collapse causes the binary tree to collapse into. The acyclic to mostly-acyclic was introduced by an anonymous edit with the summary insest exists (Sic). Since inbreeding and therefore incest can in fact not introduce a cycle into the graph (but rather two different, directed paths from one individual to another), as indicated by the creator of this talk-section, I am reverting this edit. Lklundin (talk) 19:15, 21 April 2009 (UTC)

Pity a dumbass

Hey guys - I'm a layman who is struggling to picture a last common ancestor in "family tree" terms. If the last common ancestor was part of a population of (say for the sake of argument) 10,000 humans, then does that mean that the other 9,999 don't have any descendants alive today? If not, would it be possible to produce some kind of family tree-style graphic of a mini population that has the last common ancestor labelled in an illuminatory way?Señor Service (talk) 21:37, 5 June 2009 (UTC)

I believe you mean "most recent" common ancestor, and your description is essentially sound from my limited knowledge. Aunt Entropy (talk) 01:21, 6 June 2009 (UTC)
I assume that you mean MRCA of all living humans. See section by that name. It already answers your questions, but perhaps it can be enhanced to make it even more clear. This topic is very hard to explain in a nutshell. Many people including myself have spent a lot of time to make it concise yet clear. But there is always room for improvement.
In short, the family-tree-style MRCA of a group of people alive today is simply the most recent person in the past who can be traced back to if you start from any person alive today, via Sexual reproduction. Notice that this MRCA may not have a single gene left in today's living people, because of sexual recombination (as part of sexual reproduction).
But you are right, an illustration will help tremendously to clear confusion. To answer your question, let's say that the MRCA of all living people today happened to have lived within a past population of 10,000 people. Some of these rest 9,999 people may have passed down their genes to living people today, and in fact may even have more genes present in today's population. But none of these 9,999 people can claim ALL living people as descendants. The MRCA is just the lucky guy to have covered all living population, today. Tomorrow, the MRCA may change, as living population changes. Fred Hsu (talk) 03:30, 6 June 2009 (UTC)
And if you are still curious, I wholeheartedly recommend River out of Eden. It is a fascinating read and covers all basic evolutionary background needed to fully appreciate this topic :) Fred Hsu (talk) 03:35, 6 June 2009 (UTC)

I don't get how the MRCA can be someone other than the Y-Chromosomal Adam or Mitochondrial Eve (whoever's more recent). — Preceding unsigned comment added by Deathmare (talk • contribs) 16:24, 6 June 2011 (UTC)

MRCA is just a relative label like "youngest" or "baddest". Does it make sense for me to say to you "that cat is the youngest and the baddest" without additional context? Would you know what I mean? MRCA is defined for a population of X at time Y. If you say 'matrilineal MRCA of all people alive in 2011', then we have enough 'context' to know by that you mean the Mitochondrial Eve. There are infinite number of MRCAs one can define for different population at different time.
Y-Adam and mt-Eve are not really all that special. They are only singled out because tracing and estimating MRCA via Y chromosome and mt is relatively easy compared to other genes. In theory, one could find the 'Blood-type A' MRCA of all animals, and you may find that you share a common ancestor with non-human animals in this family, while your neighbor with different blood type is excluded from your kinship. Fred Hsu (talk) 04:07, 7 June 2011 (UTC)

Thanks for the article all. Just a question to help my understanding if I may, as I like a lot of people find this tricky to comprehend! Is it true to say that, theoretically, tracing back to the identical ancestors point for a population could give you a population that would be considered a different species? I'm thinking this situation could arise if one has to trace back a particularly long way back in time, or if the present population has come to be through convergent evolution. Kurisu rs (talk) 13:40, 25 July 2011 (UTC)

A Wikipedia talk page is for discussing what content the article should contain, its structure and so on, the talk page is not for discussing the topic it addresses. Is there something in the article that you believe needs clarification? Lklundin (talk) 16:01, 25 July 2011 (UTC)
While Lklundin is absolutely right that Talk pages are for helping shape the article itself, I don't think we mind questions here for at least two reasons. First, there isn't a lot of talk traffic here unlike the article's more popular siblings, say for instance, the mtEve. Secondly, I do think people ask for help to clarify things that puzzle them even after they read this article. The latter indicates that there may be stuff missing here. So I am glad to help Kurisu rs find out what is causing the problem. Fred Hsu (talk) 01:12, 26 July 2011 (UTC)
I think the problem Kurisu rs raised is not peculiar to 'the identical ancestor point'. That is just a point between MRCA of all living humans and mtEve and y-Adam. One could well ask the same question with regard to mtEve and y-Adam. All I can say is I don't know. I don't recall reading literature that speculate when our ancestor population became a different species from us, or I guess we should say, when we became a different species from the most recent population of ancestors. Fred Hsu (talk) 02:09, 26 July 2011 (UTC)
We should be clear about what the question is. I understand the different species used here to mean that today's humans cannot interbreed with our ancestors. Note that we are talking about two sets of people from different times. Fred Hsu (talk) 02:09, 26 July 2011 (UTC)
I don't think MRCA of all living human is a different species. 2,000 years is too short I think. I guess IAP is also too close. But I am only guessing. Perhaps someone can come up with real references. Fred Hsu (talk) 02:09, 26 July 2011 (UTC)
I do think this is a good question. I've seen other people ask this question before. Fred Hsu (talk) 01:12, 26 July 2011 (UTC)
Thanks for your help Fred Hsu, I appreciate it. I think what is confusing me is that I am preoccupied with the case of early life: if the first DNA-based life started in mulitiple isolated populations, evolved independently and a species came about through convergent evolution you might not have an MRCA at all for the population of this species at a given time. As time progressed then you might of course gain an MRCA because it is a relative measure - but there is always the possibility that for a given time and population; there may be none. So, I'm applying this idea to humanity - even though the empirical evidence states it is extremely unlikely that for the present population our MRCA occurred anything more than a few thousands years ago! Anyway, hope my trying to make sense of this subject makes sense! Thanks again :) — Preceding unsigned comment added by 87.114.100.90 (talk) 16:48, 27 July 2011 (UTC)
With about 3 billion base pairs it seems unlikely in the extreme that at any time in history the human race had no MRCA because "DNA-based life started in multiple isolated populations" were actually able to cross-breed. Are there any citations that can support this concept of a missing MRCA for other species ? Lklundin (talk) 17:49, 27 July 2011 (UTC)

Merging LCA into MRCA

As explained in talk sections in LCA, MRCA=LCA generally. And the MRCA article has more complete, more accurate description of concepts with properly written paragraphs and citations. I will now examine both articles and make sure we don't lose anything important and correct in LCA during this transition. For reference, the current version of LCA at the time of this transition is this version. Fred Hsu (talk) 05:57, 6 June 2009 (UTC)
I redirected LCA to MRCA. Fred Hsu (talk) 06:08, 6 June 2009 (UTC)

Call for illustrations

It is clear from questions posted on the talk page that we need illustrations. If you have ideas or will be producing illustrations, please first post here so that we don't duplicate efforts. Fred Hsu (talk) 04:23, 6 June 2009 (UTC)

But first I would like to review changes to this article since I last looked at/edited it. We can use some clean up. Also, I will probably resolve the long-standing call to merge Last Common Ancestor into this MRCA article. If you are interested in helping, please first read this talk section from LCA for where we stood by Dec 2007 on this issue. Fred Hsu (talk) 04:23, 6 June 2009 (UTC)

I am done with review and clean up of this article itself.Fred Hsu (talk) 05:52, 6 June 2009 (UTC)

Ways to find the MRCA - Section is poorly written and should be dropped

"DNA studies have a problem in telling us about the MRCA. As Chang notes, the MRCA will be much more recent than any MRCA that could ever be found in DNA studies, even if one were to study the ancestry of every single gene. The reason being that we are considering people who are simply ancestors, through any route, whether or not any of their genes actually survived the journey. As the human genome consists of roughly 232 base pairs, the genetic contribution of a single ancestor may be flushed out of an individual's genome completely after 32 generations, or roughly 1,000 years.[4]."

What DNA studies are being referred to? This paragraph is mixing two ideas, "ways to find DNA" and the clarification that the MRCA is the unqualified MRCA, not the MRCA along a specific pathway. They don't belong in the same paragraph and the grammar needs improvement. —Preceding unsigned comment added by 67.175.124.153 (talk) 04:03, 19 October 2010 (UTC)

It has been a while since I rewrote this article. The new organization and in particular this section you pointed out need to be revised and better integrated with the rest of the article. Fred Hsu (talk) 04:13, 7 June 2011 (UTC)
It's fixed. Fred Hsu (talk) 15:45, 12 June 2011 (UTC)

"As the human genome consists of roughly 232 base pairs"... Hmm, maybe [unsigned] missed out a few orders of magnitude. The total human genome base-pair count runs into billions, as mentioned elsewhere on Wiki. DJMcC (talk) 10:22, 21 April 2012 (UTC)

MCRA of Western Europeans

The article says "Other models reported in Rohde, Olson, and Chang (2004)[5] suggest that the MRCA of Western Europeans and people of Western European ancestry lived as recently as AD 1000." Could someone point out to me where in that article it mentions this? I simply cannot find it. If it's spurious, this needs pulled or changed. -- Calion | Talk 03:45, 4 May 2011 (UTC)

Mhm... will investigate... Fred Hsu (talk) 12:13, 7 June 2011 (UTC)
Got a copy of the article from the library. Reading through it now. Perhaps it is time we clean up this article again while I am at it. Since I rewrote this article in 2007, I've only cleaned it once in 2009. I guess it is time for another house cleaning. Fred Hsu (talk) 00:42, 9 June 2011 (UTC)
Wow, Wikidom owes you one, Calion. That sentence was inherited since before 2007, unchecked. See version as of 6 February 2007. That sentence is completely unfounded. I read the article twice to make sure. Now, this article By Rhode, Olson and Chang is actually very interesting, and I think current characterization of this article in this wiki article does not do it justice. I will fix this problem during the clean up. Fred Hsu (talk) 01:06, 9 June 2011 (UTC)
Now the Nature article talks about some "Supplementary Information" which unfortunately I have no access to. It is possible that the sentence surfaced from said supplementary information, but I will never know. In any case, the mention of Western European MRCA is not essential to this article. So it will be purged. Fred Hsu (talk) 01:40, 9 June 2011 (UTC)

I think I know where that came from. It comes from the mislabeled Rohde paper incorrectly attributed as a 2005 submission to American Journal of Physical Anthropology. This much longer paper does discuss European MRCA among many other things. Sigh. I now need to fix references to this paper as well. Fred Hsu (talk) 01:35, 10 June 2011 (UTC)

This is now fixed with the full rewrite of the article. I have not attempted to resurrect the Western Europe references from the 2003 paper. It's not a 2005 paper as stated before. It is 2003 and apparently not accepted. The PDF explicitly asks that it not be cited. So whoever cares deeply about this can investigate and resurrect the reference if they wish. Fred Hsu (talk) 15:45, 12 June 2011 (UTC)

Clean up 2011

Discussion in the recent section "MCRA of Western Europeans" prompted me to examine changes made since 2009 more closely. I think it is time this article is cleaned up again. Following are for my own reference. Fred Hsu (talk) 01:49, 9 June 2011 (UTC)

OK. Here are some problems with some of the edits in the past two years:

  • Haphazard insertion of data at random locations. For instance time estimates for mtDNA MRCA of Native Americans were added to the section on genealogical MRCA.
  • Repeated information. For instance, someone added a duplicated description of IAP into the genealogical MRCA section.
  • References to concepts heretofore unmentioned. For instance, a rewrite of the second paragraph of Time Estimates describes Rohde et al. considering "not just our all-female and all-male lines", before this article even discusses how genealogical MRCA differs from genetic MRCA.

There are of course a lot of new, useful information. But I feel that no one has taken a wholistic view and organized these new writings into a coherent picture. In light of new information, and the 2004 Rohde article from Nature I've just got from my library, I think the Time Estimates section should be moved out of the initial sections. It should be presented after various types of MRCAs are discussed. I will clean up the article with these principles in mind. Fred Hsu (talk) 00:55, 10 June 2011 (UTC)

Topics to be expanded and/or clarified outside of lead section:

  • genetic genealogy vs mathematical models and computer simulations
  • MRCAs derived from gene pathways necessarily arrive at longer TMRCAs, compared to genealogical MRCAs.

Topics I removed but will add back once I figure out what they mean:

  • "Variability due to multiple founding individuals will not display as a star cluster and overall variability in the Y-DNA is thus due in part to variability in the original founding population." I don't understand what the last phrase involving "overal variability" means. Fred Hsu (talk) 03:53, 12 June 2011 (UTC)

OK. I am done rewriting. The heavy listing is done. I invite everyone to examine changes and further refine this article now. I am including useful diff pages for reference. But since so many things have changed, if you really care you should use the History page to go through individual saved edits. I've provided useful edit summary to help you along. Fred Hsu (talk) 15:40, 12 June 2011 (UTC)

GA Review

GA toolbox
Reviewing
This review is transcluded from Talk:Most recent common ancestor/GA1. The edit link for this section can be used to add comments to the review.

Reviewer: Philcha (talk) 09:50, 25 July 2011 (UTC)

I'll mark Green tickY comments when I think they're resolved, highlight Red XN any that are unresolved when most others are done, and strike out any of comments that I later decide are mistaken. I'll sign each of my comments, so we can see who said what - please do the same.

I'll mark the review {{inuse}} when I'm working on it, as edit conflicts are frustrating. If you think I've forgotten to remove {{inuse}}, please leave a message at my Talk page. Please free to use {{inuse}} with your own signature when you're working.

I'll read the article through first, then give comments. --Philcha (talk) 09:50, 25 July 2011 (UTC)

Coverage

  • This article covers only Molecular phylogenetics, but the term "Most recent common ancestor" and synonyms such as LCA are equally used throughout phylogenetics, including morphological phylogenetic analyses, for example for fossil (e.g. Arthropod#Evolutionary family tree, which includes extinct and extant taxa) and extant taxa for which genomes are unavailable or uncertain or disputed. --Philcha (talk) 10:37, 25 July 2011 (UTC)
    • I think you raise legitimate questions. But I think we need to separate this into several points and address them individually.
      • Does this article address only molecular phylogenetics? I think the answer is no. Note that mtEve is genetically computed. But MRCA of all living humans is not; it is too difficult to determine genetically. Instead, mathematical models and computer simulations are used with aid from historical and archaeological records. But I think your question is a good one. We need to mark relevant paragraphs more prominently with tags such as molecular phylogenetics, etc. to help readers see these differences clearly. Fred Hsu (talk) 01:50, 26 July 2011 (UTC)
      • Morhpological phylogenetics and fossil records. You are right. That isn't mentioned. I will see what I can find on these. Besides the ones you mentioned, do you have more resources on how morphology and MRCA interact, in today's scientific world? I suppose we could mention how evolutionary family tree were drawn/debated prior to genetics as a background discussion? Fred Hsu (talk) 01:50, 26 July 2011 (UTC)
      • MRCA of diffeernt species is underdeveloped. 'MRCA of different species' could, I suppose, use additional non-genetic-based discussion. Perhaps this section could point to additional articles as 'main articles' or 'further information' articles (e.g. Phylogenetic tree). Fred Hsu (talk) 01:50, 26 July 2011 (UTC)
  • I question whether this article is needed. The MRCA concept itself is simple (2-3 sentences), especially if backed up with a simple cladogram (see {{clade}} for how to draw one). The examples, where backed with citations, could be included in Molecular phylogenetics and / or Phylogenetics. --Philcha (talk) 10:37, 25 July 2011 (UTC)
    • Is this article needed? This article is needed, and I am hoping that once you read through these sections you will convince yourself of the same. The thing is, most things covered here are covered in depth in their own articles (e.g. mtEve, y-chromosomal Adam, etc). But this article is what binds them all. These concepts are related, and without MRCA to describe how they are related, you will need to replicate the 'glue' in each article. Also note that the time estimates for various types of MRCAs are understood better in the context of other MRCAs. For instance, TMRCA of all living humans is harder to derive than to-to-mtEve. This article is the right place to explain such difference. Fred Hsu (talk) 01:27, 26 July 2011 (UTC)
    • MRCA is a valid concept deserving its own article. See how many pages out there refer to "most+recent+common+ancestor" most recent common ancestor. Do we honestly expect these people to link to other articles instead? Also note how many wikipedia articles, including those in phylogenetics, link to MRCA to help explain the concept of MRCA. Fred Hsu (talk) 01:50, 26 July 2011 (UTC)
    • Is MRCA just a bunch of cladograms? I've generate my share of cladograms such as File:The Ancestors Tale Mammals cladogram.png which I created to illustrate the long tables I populated to summarize chapters from The Ancestor's Tale. Topics described here do lend themselves to cladogram displays, for instance, Haplogroup. But to tear this article apart and sprinkle its remains everywhere does everyone a disservice. Honestly, I am not sure why I even need to defend the need for this article. It should be obvious :) Fred Hsu (talk) 01:59, 26 July 2011 (UTC)
    • I will hold the review for a week to see whether it is then up to GA standard. If it is not up to standard, I will close the review as "not listed". If you disagree, you can ask at WT:GAN for a 2nd opinion, although the original reviewer (me in this case) has the final word. --Philcha (talk) 12:09, 26 July 2011 (UTC)
      • I think you've done a wonderful job pointing out major problems with the article. Unless the article is greatly improved, your analysis (with the exception of 'whether it is needed') is spot on. I'll see what I can do. Fred Hsu (talk) 04:02, 28 July 2011 (UTC)
    • The issues raised already, including missing citations and uncertain relevance, should have been dealt with before a GA review - a GA review is a quality control system, not help in improving articles (except for minor points, and not too many), see WP:WIAGA. In short, the article was nowhere like ready for a GA review. --Philcha (talk) 11:34, 26 July 2011 (UTC)
    • Please stick to the point. Verbose rhetoric with bold headlines is just annoying. --Philcha (talk) 11:34, 26 July 2011 (UTC)
      • I use structural organization and bold style to help sort out issues. Apparently you don't find this useful. You need only state your preference and ask that I follow it. I am a flexible man. Disparaging my sincere replies simply because our preferences and views do not completely overlap is uncalled for. Fred Hsu (talk) 04:42, 29 July 2011 (UTC)
      • The first issue is whether an article is needed. At present the article largely duplicates the content of such articles as Molecular phylogenetics, Phylogenetics, Cladistics, Human evolution. Most recent common ancestor (with Last common ancestor, MRCA and LCA as redirects to it) may be useful for the few readers who are uncertain that they understand the term. There may be scope for more content directly about the term, e.g. the history of the term. Whether that would be enough to be GA is uncertain. --Philcha (talk) 11:34, 26 July 2011 (UTC)
      • There may be scope for other aspects of the concept, e.g.: the MRCA will generally extinct (possible exceptions are microbes cultured / bred in laboratories); the MRCA may largely a hypothetical construct. --Philcha (talk) 12:09, 26 July 2011 (UTC)
        • You continue to insist that MRCA duplicates content of other articles. But I think you do not see the difference between MRCA and and specific applications involving this generic concept. It almost sounds as if you were saying parent is not needed as an article since it largely duplicates the content of mother, father, family tree and such. Despite what you claim, contents of MRCA is not duplicated in these articles you point to. Fred Hsu (talk) 04:56, 29 July 2011 (UTC)
        • The article as currently stands is directly about the term MRCA. But your suggestions of adding historical aspects and discussion the fact that MRCA will be generally extinct, etc. are very good suggestions. Fred Hsu (talk) 04:56, 29 July 2011 (UTC)
    • I've not searched Google Books for "last+common+ancestor" or "common+ancestor". You may want to try these searches to see if any actually defines the term, rather than assuming that it's obvious. --Philcha (talk) 11:34, 26 July 2011 (UTC)
    • In Ruppert, Fox and Barnes' Invertebrate Zoology (2004; ISBN ), the index does not show "most recent common ancestor" or "last common ancestor", and the chapter "Introduction to Invertebrates" (p. 1-7) explains cladists without using "most recent common ancestor" or "last common ancestor". --Philcha (talk) 11:34, 26 July 2011 (UTC)
    • I've not searched Google Scholar, as it's for experts, so very probably assumes the meaning of the "most recent common ancestor" or "last common ancestor". --Philcha (talk) 11:34, 26 July 2011 (UTC)
    • You might want to try reliable "popular science" magazines such as Scientific American or New Scientist, which may give a definintion of MRCA or LCA that you can cite. --Philcha (talk) 11:34, 26 July 2011 (UTC)

I think you have spent too much time focusing on what I see as a not-called-for campaign to discredit this article based on your own personal opinion on whether MRCA is needed. This is not part of the GA-review as the policy clearly states. It distracts from your very good opinion on how to improve this article which I highly respect. I formally ask that you strike out all sections on the 'merit' of this article. Thank you. Fred Hsu (talk) 05:13, 29 July 2011 (UTC)

Structure

(sections)


I'll check with User:Dispenser/Checklinks and the DAB checker when the content is stable.

Images

I'll check the images when the content is stable.

Lead

I review the lead last, to check that all of it is based on the main text.

Proposed Changes

Clearly this article is not yet GA. Despite our disagreement on 'merit' (which is not part of QA review), I think good ideas came out of the discussion. I will document these below, and work on the article. There is no point in keeping this QA review request alive while it undergoes dramatic surgery. After Philcha strikes out the paragraphs on 'merit', I will withdraw this request. Fred Hsu (talk) 19:21, 31 July 2011 (UTC)

These suggestions should serve as a guide for further editing of this article. And when I try (or someone else tries) for GA next time, we can check off this list of items before actual GA review starts. Fred Hsu (talk) 19:21, 31 July 2011 (UTC)

Most paragraphs have no citations
The existing body of reference support all paragraphs, but these should be explicitly pointed out inline. And more reference may be added in the process as well. Follow up on many hints and links Philcha provided.
Address the difference between MRCA and phylogenetic tree
These are different concepts.
  • Highlight the relationship between MRCA and phylogenetic tree clearly, showing how it is analogous to the relationship between parent and family tree (and how it is different whenever applicable - e.g. single gene ancestry vs male/female parental lines).
  • Introduce clade and cladogram and discuss how it relates to MRCA
Plug holes in the coverage in the types of MRCAs
Clearly mark paragraphs and sections as addressing different aspects of MRCA and lineage types: morphological phylogenetic, molecular phylogenetics, famly trees (both male and female lines), single genetic markers, etc. These should be compared and contrasted. Methodologies used for different types of ancestry tracking should be clearly described (e.g. historical records vs DNA records vs fossil records).
Specifically, make these changes:
  • Expand MRCA of different species. This should point to phylogenetic tree as main article as well.
  • Add morphological phylogenetic, and contrast this against molecular philogenetics
  • More discussion on how MRCA of all living humans, as well as Patrilineal and matrilineal MRCAs, relate to family tree.
Historical perspectives
Show how the concept of MRCA changed over time. When was it first discussed? Was this concept even entertained in the predominantly Judeo-Christian culture for the most part of the Western history? Was this found elsewhere?
MRCAs are generally extinct at this moment
...with the exceptions of some microbes cultured/bred in laboratories. Some present day organisms do look suspiciously similar to the common ancestor they share with other more differently-looking organisms, but evolution did not stop for the ancient-looking organism (cite living fossils, platypus, etc).

Result - not listed

You still have not addressed the main problems, including:

  • No definition of MRCA.
  • No check that the content is already in phylogeny and/or molecular phylogeny - a lot of this article's content should be in these other articles.
  • Jumps straight into humans. Just 1 species (or genus or family, if including Homo or hominines) of the millions extant.
  • Paras with no citations, e.g. only the 2st and last paras of "MRCA of all living humans" have citations.
  • The history of the phylogeny of particular species is irrelevant except as examples, so you'd have to show that the phylogeny of a particular species is an example of some principle (e.g. MRCA in sexual and asexual species / groups).

Regretfully I conclude that this article is not of GA standard, and am marking it "Not listed". --Philcha (talk) 08:29, 5 August 2011 (UTC)

Definition lacks rigor

"In genetics, the most recent common ancestor (MRCA) of any set of organisms is the most recent individual from which all organisms in the group are directly descended."

This, to me, is too vague. What does "most recent" mean? The common ancestor which died the fewest number of seconds ago? The common ancestor that was born the fewest number of seconds ago?

Or is "recent" based not on time, but on generations? The common ancestor to a set of organisms such that none of its descendants are also common ancestors to that set, but all of its ancestors are common ancestors to that set; or something like that?

I bring this up because a rigorous definition -- at least a clarification as to whether "recent" refers to time or to generations -- is exactly what I came to this artice to find. Gaiacarra (talk) 02:57, 12 January 2012 (UTC)

Agree definition is childlike

From the opening sentence the article appears to be written by a child with a thesaurus: “In genetics” – Really? Why not “In biology,” or “In heredity” or “In genealogy” or “In evolution”? "(MRCA) is the most recent individual” – would that be the mom or the dad? “from which all organisms in the group are directly descended.” – Hmm “Directly” descended, versus the other kind?

Grown-up language such as: “Y-DNA network analysis of Y-STR haplotypes showing a non-star cluster indicates Y-STR variability due to multiple founding individuals,” is immediately followed by the childlike: “The descendants of Genghis Khan can be (traced) back to the time of Genghis Khan.”

Quote “The MRCA of living humans may have had many companions of both sexes.” A bit too salacious for the Wiki, no?

So much is made of the ”MCRA of everyone alive” and the ”identical ancestors point,” except what the difference might be. In fact, the whole article seems to have been taken over by techno-scienceo-jibberish. Reminds me of those amusing tourist signs in China like "deformed person toilet." Not quite the standard thoughtful people are looking for!

One author boldly states: “A common mistake made by the public as well as some authors is to refer to a proposed last common ancestor as an earliest ancestor.” Excuse me? Why is it a mistake? Who knows?

Dlong2 (talk) 15:58, 5 July 2012 (UTC)

Thank you Skates61

Rohde, Olson and Chang’s paper is granted only a small reference. But take away their contribution and this article is basically just a statement that the term “Most Recent Common Ancestor” can be represented by the letters M.R.C.A. I’d turn it into a stub with a reference to the paper and leave it at that. Dlong2 (talk) 16:02, 5 July 2012 (UTC)

MRCA 60-80-thousand years ago?

What about really remote people? I would have thought that the MRCA of all humans would have lived before the ancestors of non-Africans left Africa. that is 60-80-thousand years ago. --Oddeivind (talk) 21:58, 21 July 2012 (UTC)

That assumes no interbreeding since then... AnonMoos (talk) 15:30, 25 July 2012 (UTC)
It suggests no interbreeding with the more distant human groups. Most human groups have interbred a lot since then, but there are still groups in e.g. Amazonas that have had little contact with non-indigenous groups. The same is probably true with distant groups in other parts of the world. If you look at the MRCA for the majority of the human world, e.g., it semme slikely that this might be just a few thousand years back, but if you include absolutely everyone, these seems very unlikely indeed. --Oddeivind (talk) 10:19, 26 July 2012 (UTC)
Tasmania is a famous example of almost 10,000 years of isolation, but the same is not true of the Amazon area. Where is the example of 60-80,000 years of absolute (not relative) isolation?? -- AnonMoos (talk) 16:29, 26 July 2012 (UTC)

MRCA changes as new people are born and old die?

Ok, I buy that it changes when people die without descendants because you can then clip them out of the human family tree. But new people born are by definition descendants of parents that already share a MRCA, so how can that change the population's MRCA?Consuelo D'Guiche (talk) 12:31, 25 July 2012 (UTC)

The MRCA can change if the last member of the most remote and isolated groups becomes extinct. The MRCA would change from the last person who was an ancestor of that group, and everybody else, to a later individual who was the most recent ancestor just of the everybody else. -- 12:29, 8 March 2013‎ Eregli bob
I think MRCA can be defined in two different ways: 1. the most recent person whom we all have inherited some genetic through, and 2. the most recent ancestor we all share (but whose genes might not be shared by all). When the oldest branch dies out, the latter becomes more recent, but the former not necessarily. On the other hand, when somebody is born, recombination may lead to the shared alleles being lost, and MRCA then becomes earlier. User:Ketil — Preceding unsigned comment added by 77.88.93.100 (talk) 13:01, 24 October 2014 (UTC)

Strange Claim

I find this claim highly dubious: ""No matter the languages we speak or the color of our skin, we share ancestors who planted rice on the banks of the Yangtze, who first domesticated horses on the steppes of the Ukraine, who hunted giant sloths in the forests of North and South America, and who labored to build the Great Pyramid of Khufu".[4]" I realise it is in a certain context, but, is there genetic evidence to support it, or is it merely maths based speculation??? It seems sort of unlikely that people from very opposite parts of the globe (say for instance a person from Africa having South American ancestry) would be related in this way, considering how these areas were populated and the amount of time it took people to travel pre-modern transport. I sort of question its presence for that reason^, that said I didn't read the paper so who knows :D — Preceding unsigned comment added by 72.228.182.191 (talk) 03:34, 5 February 2012 (UTC)

Apart from the fact that such prose is non-encyclopedic, it is also not true. My known ancestors, for example, came from Europe and therefore were probably not descended from Chinese. It would be more accurate to write "All humans share ancestors who emigrated from Africa." Or "All humans share common ancestors with people who plant rice on the banks of the Yangtze..." Greensburger (talk) 06:21, 5 February 2012 (UTC)
It would be out of place for us on Wikipedia to write in such a way on an article, but I don't see why we can't quote it from a scientific paper... AnonMoos (talk) 02:56, 5 March 2012 (UTC)
I will remove the quote: It talks about multiple ancestors that are more remote than the MRCA and is therefore irrelevant to this article. Lklundin (talk) 14:56, 5 March 2012 (UTC)

The quote is the last sentence in the 2004 nature paper by Rohde, Olson and Chang that forms the basis of much of the material in the article and should be restored. Skates61 (talk) 16:50, 3 June 2012 (UTC)

This raises an important issue. People find it very difficult to visualise the speed at which genes spread through the population. Possibly this is because languages and cultures remain geographically fixed. Perhaps this scepticism needs to be addressed in the article? — Preceding unsigned comment added by 194.150.177.249 (talk) 11:16, 13 November 2013 (UTC)

Can we please get a geneticist to refute some of these young-earth claims of a 3,500 year-old human ancestor? It is really annoying to have people who claim that the earth is 6,000 years old to point at Wikipedia as their source, saying the human species originates at 3,500 years ago. I am not a regular contributor to Wikipedia, but this MRCA claims of 3500 years are unsupported by genetic evidence. — Preceding unsigned comment added by 63.229.209.73 (talk) 06:53, 28 February 2016 (UTC)

Problem wit Identical Ancestors Point

I have made some changes in that section and, been no native english speaker, I absolute agree with having been corrected. But before erasing my contribution you should read carefully it and the article of IAP: this is NO SCIENCE at all, but a fallcious huge mountain of biased lies. This part of the article is absolutely false and fallacious. It tends to probe a thing in scientific-like lenguage with no scientific thought in it at all. People is not getting it SIMPLY BECAUSE ITS FALSE. There's no proof of such a thing as IAP to have happened in the past, for sure not MANDATORY and statistically VERY uneven. And if, by some very weird chance, this thing happened in the past it only could be in the population bottleneck of 75.000 years ago, BUT THERES NO GENETIC OR OTHER proof for that; or going back and back in life history up to the very beginning of pluri-cellular life.

What I clearly see is the long hand of religious crap underneath it all: the date of 5.000 years is such a joke in terms of MRCA and historical proofs of isolated populations that can only came from the crapy young earth creationists. I don't want and really don't think it worths my time fighting with fanatics or well paid guys (hi, Heritage guys!) to begin an editions war but I beg for someone with wiki authority to have an eye on this before we begin to hear this crap as a 'scientific proof for Adam and Eve and original Sin supported by wikipedia' in the media.

For the supporters of that crap: I wish all your ignorance presents its bill to you soon.

I just want you editors to read things critically and using your reason and mind. Please, please have an eye on this. — Preceding unsigned comment added by Cohelet (talk • contribs) 20:49, 19 March 2013 (UTC)

Don't post this crap here. The talk page is for dicussing ways to improve the article. Nobody cares about your opinion. Your opinion doesn't matter here. Where is your proof that it's all a lie? Why have you not provided reliable sources to back up your claim? Why are you under the impression that this article implies there is scientific proof for IAP? It does not. Dkspartan1 (talk) 06:00, 20 April 2013 (UTC)
Cohelet -- regardless of what the effects of the Toba volcano may have been, it seems quite likely that multiple episodes of human evolutionary change took place within relatively small populations (since it's easier for a mutation to establish itself in a small population than in a large population etc.). The transition from 48 chromosomes to 46 likely took place within a relatively small population. A species having a relatively small population for number of generations means that the identical ancestor point is not too far back. Also, if the living members of a "species" don't have identical ancestors until several branchings up on the tree of species differentiation, then it's not likely to be a valid species at all... AnonMoos (talk) 08:03, 20 April 2013 (UTC)

I posted this to WT:GENETICS in response to the concerns of another editor which came up at WP:EAR: I actually just read the Rohde et al. article. It actually doesn't say anything about "5 to 10 thousand years ago". I tried to wrap my head around their statements to see if I could independently arrive at the article's 5 to 10k years ago claim via routine calculations, but could not. There are several statements about mean identical ancestor points arrived at in their simulations depending on changes to variables and the models, placing it at 2,158 BC, or 5,353 BC, and also noting that if people in Tasmania were totally reproductively isolated until 1803, then the latest possible identical ancestor point corresponds to the flooding of the Bass Strait some 9,000–12,000 years ago. Honestly, I think this is far enough away from routine calculations to make the claim in most recent common ancestor constitute original research. At the very least it probably needs in-text attribution to the authors. —/Mendaliv/2¢/Δ's/ 20:02, 20 May 2013 (UTC)

So, what, should this be removed? Corrected? I don't know enough about this subject to properly address it but I know it doesn't click. TangoFett (talk) 14:17, 6 April 2015 (UTC)
Yes, I have removed it. The paper was about a trivial model, making very simplistic assumptions about migration. The paper has scientific merit in showing how migration affects the IA, but the numbers coming from the model are clearly nonsense. 13:33, 27 July 2015 (UTC) — Preceding unsigned comment added by LachlanA (talk • contribs)
I am not sure you appreciate they calculate the MRCA for 2004, and not for 1803. Clearly, the MRCA before 1800 would have been very ancient indeed. But after contact, it doesnt take more than a few generations to spread admixture throughout the recently-contacted population, radically reducing the age of the MRCA. I am sorry if I am misreading the above and you are in fact aware of this. --dab (𒁳) 13:00, 21 October 2016 (UTC)

unwatched? semiprotect?

I am kind of losing hope for this page. I visit it every couple of years and clean up the worst attrition, but somehow, utter misconceptions always pop back almost immediately and remain unchallenged (in this case, since 2012). I'll try to clean up the page once again, but if you are watching it, please be wary of people adding "explanations" without citing additional sources. --dab (𒁳) 13:06, 21 October 2016 (UTC)

Exact meaning of "most recent" in genealogy

The first sentence of the article says: In biology and genealogy, the most recent common ancestor [...] of any set of organisms is the most recent individual from which all organisms in a group are directly descended.

Focussing on genealogy here, and taking two (distant) cousins as any set of organisms, the meaning of the term most recent individual is possibly confusing. In (genetic) genealogy, MRCA often refers to 'most recent in terms of fewest generations back', and is used in the context of comparing DNA test results. For example, in the case of two second cousins who share a great-grandparent born in 1850, and who (via a different path) also share a greatgreat-grandparent born in 1860, the great-grandparent would be the MRCA for genetic genealogy purposes, but the greatgreat-grandparent would be the MRCA in the more common meaning discussed in this article. Generation gaps can be quite different in different ancestry lines, so this situation does happen in family trees, especially if you go back more generations than 3 or 4.

Since genealogy is mentioned in the lead sentence, I think it would be good if the article would clarify the exact meaning of "most recent". Does anyone have more knowledge about this? I can't find good sources that clearly define MRCA in genealogy context. Gap9551 (talk) 18:42, 12 October 2017 (UTC)

Two more sources

[2] and [3]. Doug Weller talk 18:05, 17 July 2018 (UTC)

Problem with "cats and dogs"

"for example, the MRCA of all Carnivora (i.e. the MRCA of "cats and dogs") is estimated to have lived of the order of 42 million years ago (Miacidae).[4]"

Carnivora are lions, tigers, bears, as well as canids. The MRCA of Canids is 60 million years ago. Canids include dogs, wolves, etc. — Preceding unsigned comment added by 208.80.117.214 (talk) 09:32, 1 September 2018 (UTC)


TMRCA of all living humans

In this section of the article is the following statement: "The age of the MRCA of all living humans is unknown. It is necessarily younger than the age of either the matrilinear or the patrilinear MRCA"

Does anyone else see a flaw in the logic of that statement? If the most recent common ancestor of all living humans is necessarily younger than the age of either the matrilinear or the patrilinear MRCA, then who/what was this ancestor, if they were neither female or male, and how did they pass down their genetics? If they were in fact, as all logic would suggest, either male or female, that would make them either the matrilinear or the patrilinear MRCA and thus the exact same age as one of them, not necessarily younger than both.

Therefore I must conclude one of the following:

  • the statement is completely illogical and untrue
  • the wording in particular the use of the word "either" leads to a misreading that in my opinion is a very easy misreading
  • there's not enough emphasis that MRCA uses a different model to predict TMRCA than mt-MRCA or Y-MRCA does. I would argue if the non-genetic, mathematical models and computer simulations are biased to always produce lower values, or the gene-marker based models are biased to always produce higher values, or indeed both, that the biased model is inherently flawed due to that bias. But I'm not an expert in this field and that's a tangent to the point of this comment which was: The quoted comment is either false or very confusing. If this third case is the correct conclusion, more emphasis should be placed on the biases of the models when making this statement, ie: "Due to biases within the modeling methods, the age of the MRCA predicted by the non-genetic, mathematical models and computer simulations will be younger than the ages of the matrilinear and patrilinear MRCA predicted by the gene-marker based models." Then perhaps expand on why that is, ie the mathematical models make assumptions about mating practices, while the gene-marker models make assumptions about mutation rates, etc. The assumption about mating practices skews results younger because... The assumption about mutation rates skews results older because...

As I said, I'm not an expert in this field, would someone that has more knowledge on the subject be willing to clean it up? — Preceding unsigned comment added by 198.47.204.197 (talk) 14:01, 10 September 2018 (UTC)

The statement does make sense but it could be more clearly expressed. Matrilinear MRCA means solely through the female line, ie mother, grandmother, great-grandmother etc. Generic MRCA means that the descent can go through the father or mother in each generation, eg mother, grandfather, great-grandmother. Dudley Miles (talk) 14:45, 10 September 2018 (UTC)
I'm still having trouble understanding, if generic MRCA is male, wouldn't all Y-chromosomal DNA have to have come through him as well; Similarly if MRCA is female, all mitochondrial DNA? Therefore MRCA is also either mt-MRCA or Y-MRCA. Could you provide an example tree where MRCA is not also mt-MRCA or Y-MRCA? 198.47.204.138 (talk) 15:08, 10 September 2018 (UTC)
Generic MRCA could have been either male or female and goes through both lines. In each generation it can go through either the father or the mother, eg mother, grandfather, great-grandmother or father, grandfather, great-grandmother etc, wheareas mt-MRCA has to go through solely through the female line, mother, grandmother, great-grandmother. Ditto Y-MRCA father, grandfather, great-grandfather. Dudley Miles (talk) 15:28, 10 September 2018 (UTC)
It took me a while to draw it out, I had to consider the case that a male that had all female offspring before it hit me. That man could be MRCA, but he would have passed on no Y-chromosomal DNA, and thus wouldn't be eligible for Y-MRCA. So I now understand it's not the case that MRCA must necessarily be Y-MRCA or mt-MRCA, but I would say that it's also not necessarily the case that MRCA must necessarily be younger than both Y-MRCA and mt-MRCA, because while I now understand it's not necessary, it is still possible that MRCA and Y-MRCA are the same individual. Some example family trees that illustrate the various possibilities, I believe would be very helpful in helping people understand. 72.37.1.7 (talk) 16:20, 10 September 2018 (UTC)
The MRCA is "necessarily" younger than mt-MRCA or Y-MRCA in the same sense that if you flip a coin 500 times, it will "necessarily" come up tails some of the time. It is technically not impossible that the overall MRCA is the same individual you'd get to by tracing back only fathers (or mothers), or that the coin comes up heads 500 times in a row, but in practical terms, these outcomes are inconceivable: so unlikely that the possibility does not merit a mention.Rracecarr (talk) 16:57, 10 September 2018 (UTC)
  • Redefining a word doesn't seem like a very strong defense.
  • my original impression was that MRCA must necessarily be either Y-MRCA or mt-MRCA. Since the opposite is extremely likely(as you point out) to be the case, wouldn't it be good to actually say that, and maybe explain why? You know, avoid the confusion altogether. Two graphics showing a 4-5 tier family tree with Y-MRCA, mt-MRCA, and MRCA labeled, one where they're all different individuals, and one where MRCA and either Y-MRCA or mt-MRCA are the same, and a small blurb about why the second is highly unlikely, seems reasonable to me. If you want to get really involved, I guess you could make different cases for Y-MRCA being older than mt-MRCA and vice versa. 72.37.1.7 (talk) 17:23, 10 September 2018 (UTC)

[outdent] Just defining, not redefining. Many things that are impossible are so because they are so highly unlikely. Such as all the oxygen molecules in a room randomly moving to one end, suffocating someone at the other end.

I think the graphics you describe could be helpful. Knock yourself out. Rracecarr (talk) 17:35, 10 September 2018 (UTC)

Necessarily ≠ Highly likely, Impossible ≠ Improbable or Unlikely. Your example is a false equivalence, all oxygen molecules in a room randomly moving to one end, suffocating someone at the other end, actually is impossible to the best of my knowledge, air being a combination of ideal gasses; you've already ceded the point that it's possible however improbable, and I've already ceded it's improbable. At this point the argument is pedantic on both sides, and perhaps of lesser concern. I'll start on some graphics. — Preceding unsigned comment added by 72.37.1.7 (talk) 18:03, 10 September 2018 (UTC)
I can't seem to add graphics, here's a link to one example I created. It's free for anyone to use for any purpose. Example Image Leiasolo527 (talk) 22:11, 10 September 2018 (UTC)
I think a good and simple explanation can be a few paragraphs of text starting with "Imagine the world population consisting of just a few closely related children" describing a population easy to grasp with just words (her kids, his kids, their common kids) and their parental hierarchy i.e. a prose model even simpler than your graphic.Cobanyastigi (talk) 10:22, 11 September 2018 (UTC)
If you think you can accomplish it with words, go for it! I'm a visual and hands on learner, graphics work better for me personally, but a well written article works. I'd be happy to review and provide any feedback for whatever wording you come up with. Leiasolo527 (talk) 15:54, 11 September 2018 (UTC)
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