|Text from Linebreeding was copied or moved into Inbreeding#Domestic animals with this edit. The former page's history now serves to provide attribution for that content in the latter page, and it must not be deleted so long as the latter page exists. The former page's talk page can be accessed at Talk:Linebreeding.|
|WikiProject Genetics||(Rated Start-class)|
|WikiProject Evolutionary biology||(Rated Start-class, High-importance)|
|To-do list for Inbreeding:|
|This article was nominated for merging with Linebreeding on 10 August 2008. The result of the discussion was merge.|
- 1 22-36% risk
- 2 Vandalism?
- 3 Westboro Baptist Church
- 4 Endogamy merge?
- 5 External link
- 6 Jewish Law
- 7 Pignatelli case
- 8 Outbreeding
- 9 Charles & Diana
- 10 Editing
- 11 POV?
- 12 Natural Selection
- 13 Domestic Animals
- 14 Bad Assumptions
- 15 Moved The Rothschilds from the article here for verification.
- 16 Charles II of Spain
- 17 Mormon
- 18 Inbreeding depression
- 19 Cleopatra
- 20 information available for use in this article
- 21 Father-daughter inbreeding as reproductive strategy
- 22 Merger proposal
- 23 Ancient Egypt section inconsistencies
- 24 Genetic Diversity in a population
- 25 Interesting statistic
- 26 Contradiction
- 27 Dead link
- 28 Genetic purging
- 29 Allele exposure
- 30 Icelandic Study
- 31 Edits
- 32 Other Notable Cases of Human Inbreeding?
- 33 Inbreeding in Ancient Egypt was widespread
- 34 Please fix this sentence
- 35 Overpopulation Inbreeding
- 36 Tests for Inbreeding
- 37 Cheetah inbreeding
- 38 Darwin
- 39 Results
- 40 Coancestry Calculation
- 41 Artificial Insemination
- 42 Pharaohs
I removed a bit about 22-36% of first-degree incestuous offspring being at risk of birth defect as it was not support in the citation given. Citation can be read here: http://www.amazon.com/Inbreeding-Incest-And-The-Taboo/dp/080474596X The increase is not in terms of total population, but over background rates; in other words, in 1 in 100 non-incestuous offspring are at risk, then 1.22 to 1.36 in 100 incestuous offspring are at risk, not 23-36 of 100. This is made even more clear when you access the cited work by Bittles. I didn't know how to reword this, so I deleted it.
"Roughly 20% of the world's marriages are between first cousins" ?! This is absolutely unsubstantiated! It's like saying: "90% of all Europeans are direct descendants of, say, Caesar :)" or something like that. I am going to delete this now because stuff like that makes Wikipedia hugely unreliable. I do understand that what was probably meant is that, throughout human history, there was a lot of inbreeding. This might be true, yet I'd like to see some data to support such a statement. I'm deleting this sentence now. —Preceding unsigned comment added by 220.127.116.11 (talk) 20:58, 14 December 2009 (UTC)
Westboro Baptist Church
Why was this even included? Westboro Baptist Church
The church group (and alleged cult) Westboro Baptist Church has apparently begun inbreeding, with one of its members, Rachel Phelps, being married to her nephew's brother-in-law, Charles F. Hockenbarger (her newphew, Samuel Phelps-Roper, is married to Charles' sister, Jennifer). Additionaly, though it does not interfere with genetics, Shirley Phelps is married to her step-brother, Brent D. Roper. Long before these marriages took place, residents of Topeka speculated that the church's stringent guidelines against marrying outsiders, coupled with the lack of potential spouses within the group (nearly 90 of the group's 100 members are related through blood or marriage) would lead to eventual inbreeding. It is unknown whether this pattern will continue or, if it does, how extreme the degrees of inbreeding will become.
There is no genetic relationship in the above case. Anything else is speculative. Phelps is married to her adopted brother if you read the article on Roper. Whatever our own feelings about the church, I think that bit doesn't add to the article and wasn't motivated by a desire to improve the article.
Comatose51 18:54, 23 October 2005 (UTC)
How about merging this article with the endogamy article? Maybe the inclusion of the Ashkenazim, also.
Moved this here.
- Inbreeding also occurs in humans. For example, Japan is one of the most endogenous societies in the world.
It doesn't seem clear to me that 1) Japan is more endogenous than say Iceland and 2) this can be regarded as inbreeding since the rate of genetic and health problems in Japan isn't higher than the rest of the world.
- "one of the most" :teach: 18.104.22.168 23:01, 22 March 2007 (UTC)
I don't care who is singled out but I do need at least one example of it in humans.
From the link I gave:
One of the most endogenous societies in the world, Japan has approved of incestuous marriages in court circles even in historical times.(152) Preferred sibling, cousin, uncle-niece and aunt-nephew marriages have been so extensive that genetics experts have discovered that the inbreeding has affected their size and health.(153) How often this incestuous marriage system occurred in traditional Japan is still largely unexplored. One indication of what is likely to be found is a 1959 study by Kubo showing that there were still rural areas in Japan where fathers married their daughters when the mother had died or was incapacitated, "in accordance with feudal family traditions.(154) Kubo concluded that incest was considered "praiseworthy conduct" in many traditional rural families. In the 36 incest cases he studied in Hiroshima, he found that there was often community moral disapproval of the families who lived in open incestuous marriages, but that the participants themselves did not think of it as immoral. In fact, when the father was unavailable to head the family, his son often took over his role and had sex with his sister in order "to end confusion in the order of the home." Other members of the family accepted this incest as normal.
1) Consider the possibility that you can't find an example because there isn't one.
2) Japan has a population of 150 million. Finding a few dozen or even a few thousand cases of incest isn't near enough to label the population as inbreed.
No way. Incest is very prevalent in Japan. It's a question of finding a population that's inbred.
There should be something about inbreedding depression, and perhaps something about breeding culture with animals, where they recommend an inbreeding coefficient around 1-5% as far as I remember. Outbred isn't always recommended.
This whole paragraph needs rewriting:
- The only really major problem with inbreeding is that two closely related individuals are likely to have very similar genomes, and if one individual has a gene for a given negative trait, then the other is likely to have it as well. It is pretty complex, and I would spew numbers, but I'm sure any reasonably intelligent person can figure it out for themselves with a basic knowledge of Gregor Mendel and his plant breeding experiments. Suffice it to say that a single instance of inbreeding is statistically very unlikely to result in a flawed individual.
-- The Anome 09:09, Jan 26, 2005 (UTC)
I wonder about the link Consanguinity and Mating. While it's got a lot of historical anecdote, it needs at least some kind of context as it comes from the site for Anthony M. Ludovici: not exactly a mainstream take on the subject!
- I agree, and I've removed it. --Xyzzyplugh 01:00, 13 February 2006 (UTC)
In Jewish law it is not incestuous for a man to marry his brother's daughter, but does the same apply to marriages between a man and his sister's daughter? The reason this occurs to me is the definition of a Jew as being a person "with a Jewish mother". This suggests a previous matrilineal kinship system, where those related through the female line might be forbidden to marry, but those related only through the male line were not. Can anyone give further information? Too Old 09:45, 9 January 2006 (UTC)
Erm, not highly relevant to its subheading, since they were not royalty.
Anyway, there have been better examples, for example uncle-niece or aunt-nephew marriages.
- Pignatelli was a case of extraordinary generational differences of descent found in some alliances among royalty and nobility. I can rename the heading. Charles 16:28, 27 April 2006 (UTC)
"Outbreeding" is linked in the article, but redirects here! The word is not explained in this article, but one could assume that it is the opposite of inbreeding.
- the link be removed,
- a new article created,
- an inline definition be added,
- or, a link to something similar (i.e. Miscegenation) be inserted?
(No, I'm not bold!) CAD6DEE2E8DAD95A 16:58, 9 May 2006 (UTC)
Charles & Diana
they are left off the list as is the other royals.. Charles & Diana are 3rd cousins.
- No, they are not. Their closest relationship is of 7th cousins, once removed. It is non-notable as many, many, many people are related to that degree or closer. Charles 16:29, 11 May 2006 (UTC)
I've done a fair bit of rearranging and added a small amount of material I think it makes more sense now, and am removing the tag. --Michael Johnson 12:20, 11 July 2006 (UTC)
- Intermarriage in European royal families is no longer a problem, due to modern science and our understanding of the negative consequences
Does this sound a little POV to anyone? I understand what they're trying to say, but it sounds a bit off to me.--Stella luna 18:32, 27 July 2006 (UTC)
- Yes, it is POV. It is widely assumed, but without any reliable evidence, that intra-marriage among royal families caused genetic "problems", e.g. in King Charles II of Spain and the so-called Habsburg lip. But no one ever cites what precise medical condition caused the problem, nor how it was caused or aggravated by inbreeding (rather than, say, multiple-generation inheritance of a dominant gene) -- and the Habsburg lip is not usually a "problem" at all. Rather, people tend to assume that if a person has an observable defect, and if that person has inbred ancestry, then the deleterious trait must be due to the inbreeding -- mistaking correlation for causation. Whereas we know, due to subsequent improved genetic and medical information, that in famous cases where it was popularly assumed that inbreeding was the source of a congenital defect, it had nothing to do with inbreeding: For example, the historically disastrous hemophilia among the descendants of Queen Victoria of the United Kingdom and her husband/first cousin Albert, Prince Consort. Despite frequent intra-marriage among that couple's descendants, not a single incidence of royal hemophilia is now attributed to inbreeding. Another example is the mental retardation of Prince François, comte de Clermont (and of his sister, Princess Blanche, born 1962), the heir apparent of the current Orléanist pretender to the defunct French throne. Four of Clermont's paternal great-great-grandparents were first-cousins, plus his mother and paternal grandmother also descended from multiple cousin-intramarriages. Nonetheless the retardation turned out to be due to his wife's infection with toxoplasmosis. And of course, nobody wants to mention in this context the brilliant, irresistable and fertile Cleopatra, who descended directly from seven generations of brother-sister marriages. The correct rule-of-thumb here is not "Don't marry your kin", but "garbage in, garbage out -- yet the reverse is just as likely to be true: matings of healthy relatives may produce healthier offspring." Lethiere 21:13, 8 December 2006 (UTC)
While researching inbreeding in humans, I have found reference to the above comment, along with citations of problems with populations that have high homozygosity. It has also been found that some human populations with isolation, and documented genealogies, are relatively free of genetic illness, even though homogeneous. In humans, however, isolation has not generated the races or "breeds", that some researchers such as Sir Arthur Keith, Coons etc. cited in their writings. The current genomic tracings of humans are indicating (relatively) small genetic diversity throughout our species. We have few progenitors,indicated by our mtDNA and the y chromosome, in comparison to many other animals. I am looking for a reference that indicates that our currently known genetic diversity would optimal for a population of 10,000 individuals. I intend to revise the article further on humans. It needs full revision as it is mostly POV. --Kerheals 19:12, 7 January 2007 (UTC)
- Our homozygosity is a function of our youth as a species. When compared with Chimps the most distantly related humans display less genetic diversity than chimpanzee siblings.--Counsel 20:30, 8 January 2007 (UTC)
Youth is a nominative adjective, it is an interpretation of what is found. Technically so are our definitions of what is "human".
In humans, we find such occurences of one male producing millions of descendents through his conquests and raids. This "inbreeding" has produced the y chromosomes AND mtDNA most present in the population. There is NO sign of inbreeding depression in the general population.The radiation of the genetic traits, and its ubiquitous increase of population associated with radiation has caused this. Naill of Noigiallach and Genghis Khan have great expression throughout the population. These warriors and raiders had many "wives" and therefore represent a preponderance across the population. It is NOT so much the youth of humans, but the tendency towards population bottleneck, with subsequent genetic drift of the founding genes have produced this finding. WE reduce our genetic pool by our social conflict. And by the way, so do chimpanzees when they raid other groups adjacent to their home territory.--Kerheals 14:32, 16 January 2007 (UTC)
Mandibular prognathism has not been fully identified as a genetic trait. It is SUSPECTED to be so. The trait has not been identified as either recessive or dominant. It has been found to run in families in Japan as well. [[ http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=16214628&dopt=Abstract]] --Kerheals 04:35, 30 January 2007 (UTC)
- It is possible for a population to become inbred without inheriting deleterious traits. For instance the cheetah is a highly inbred species, resulting from a population bottleneck. Many island species are also highly inbred. This is more likely in a population where natural selection is acting. I'm pretty sure natural selection is always happening, it's not something that you can turn off.
I think the answer is Yes, if I understand the question --Michael Johnson 12:34, 4 October 2006 (UTC)
We have what appears to be good information there, however, it should be kept in mind that the goal is description, not advice on how any particular editor believes breeding should be done.--Counsel 20:06, 8 December 2006 (UTC)
Much of this article is written with the assumption that a breeder is infallible. Take the following paragraph for instance:
- "Natural selection works to remove individuals who acquire the above types of traits from the gene pool, therefore many more, in the first generation of inbreeding, will never live to reproduce. In biology, the fittest are those who survive and breed. Over time, with isolation such as a population bottleneck, caused by purposeful (assortative) breeding or natural environmental stresses, the deleterious inherited traits are culled."
Firstly, it is a poor assumption that "many more" of the first generation will never live to reproduce. Tp what organisms does this refer? Brine shrimp? Sea Turtles? Trees? Dogs? People? It is not possible to generalize over such a broad spectrum. The second sentence states that only the fittest survive in biology. This may be true of collage biology courses, but not of all organisms. In nature the fitter animals are more likely to survive and reproduce, but in fact all might survive in any given generation or all might perish. It depends upon what organism and what environment we are talking about. Lab rats with horrible defects might survive, sea turtles in the wild might not. The next sentence states that "assortive breeding" culls deleterious traits, ipso facto. This assumes that the person controlling the breeding is able to identify the traits, knows how to eliminate them, and chooses to avoid them. If this were true even most of the time such things as hip dysplasia would not exist in dog populations. In fact, they are increasing. The omniscient breeder assumption that pervades this article needs to be culled.--Counsel 23:05, 21 December 2006 (UTC)
The omniscient anti breeding status of the previous article was not based in genetics. The fittest in biology may not be the "best" choice or the most beneficial for the survival of the species, the article now fairly presents what the issues are in inbreeding. In the first generation(not necessarily a single breeding, statistics show that no deleterious phenotypes are also probable) of inbreeding deleterious traits are most often expressed, that is a fact in ALL organisms, it is a basic tenet of Mendelian genetics. The article previously made no distinction between the "fittest" in a biological sense and the "fittest" in the sense of survival in terms of "strength" and vigor. It is a theoretical error to assume that the strongest survive. This is not always the case, specifically with recessive deleterious traits. The previous article made an error in terms of its emphasis on the strength and vigor. The fittest in biology are simply those who survive and breed. Casual or "backyard" breeders have been responsible for the over expression of deleterious traits in both cattle and domestic companion animals. Such breeders are not assortative(and therefore not in the best interest of a breed) at all. Assortative breeding must, by definition, take the various genetics views into account, and must include requisite culling, which can be distasteful when we are discussing humans. If a breeder is not aware of the traits, then assortative breeding is an impossibility.The article now discusses how to identify the traits, identifies culling as the means of removal, and identifies the benefits of removal by culling. Culling may be accomplished by either euthanesia , natural death(selection) either in utero or after birth, or by sterilization of those who express genetic illness. The previous versions were far to close to the animal rights view, which is by nature, anti breeding. In fact there were many errors of fact, and presentation of genetics theory, specifically in the discussion of cheetahs. Finally what purpose is the discussion of royal families? A previous talk participant pointed out the errors in the outcrossing paradigm that was present within the arguments. Why is it that no changes were made on the entry? --Kerheals 17:11, 24 December 2006 (UTC)
Moved The Rothschilds from the article here for verification.
===The Rothschilds=== Among the descendants of Mayer Amschel Rothschild, the founder of the famous financial and banking family, many of the men married their brothers' daughters or cousins related through the male line, neither of which practices is forbidden by Jewish law. They also had the tradition that only male descendants in the male line could participate in the business, though daughters did inherit considerable wealth. These two traditions were a means of keeping the business closely in the family. This was the reason that, in 1901, the Frankfurt branch of the family business was closed when the male line that managed it died out.
Please provide a source. I know the entire article is unverified, but this is rather controversial, especially "neither of which practices is forbidden by Jewish law".--22.214.171.124 14:50, 19 March 2007 (UTC)
Charles II of Spain
- I know that it has to be tagged without evidence, but come on ;-) Charles 16:05, 7 April 2007 (UTC)
- This debate seems to have died due to lack of interest. I am removing the tag. As Charles II's disabilities are widely attributed to his very inbred lineage, it is unnecessary to tag a photo caption. Someone probably should add a cite sometime, though. Montanabw(talk) 03:26, 23 September 2007 (UTC)
- The "debate" has not died due to lack of interest. Rather its point has been vindicated because no one has supplied the requested documentation of the allegation's accuracy. "As Charles II's disabilities are widely attributed to his very inbred lineage, it is unnecessary to tag a photo caption" is an affirmation of hearsay. But people turn to an encyclopedia to learn whether hearsay is accurate, so it is inappropriate to simply affirm it or squeeze it in merely because it is popular hearsay. At least that is my reading of Words to avoid, Weasel words, and the Bandwagon fallacy. The fact that the unsupported allegation is made in a photo caption makes it no less inappropriate. Several examples of popular but inaccurate historical assumptions about royal inbreeding were cited (at Talk:Inbreeding#POV?) as evidence of why this article should not repeat unsubstantiated genetic rumors. I'm giving the caption a weasel tag. Lethiere 06:30, 23 September 2007 (UTC)
- This debate seems to have died due to lack of interest. I am removing the tag. As Charles II's disabilities are widely attributed to his very inbred lineage, it is unnecessary to tag a photo caption. Someone probably should add a cite sometime, though. Montanabw(talk) 03:26, 23 September 2007 (UTC)
Oh for crying out loud! Haven't you ever cracked a world history textbook? This is about the most classic and well-known example of why first cousins shouldn't marry in all of world history! This is so silly. You want sources, fine. It is most certainly not hearsay, though at the time he was said to be bewitched? Shall we move the reference to the magic article? Sheesh! Spend your time tagging dubious and unverifiable claims, for pete's sake. Stay tuned for sources. What a waste of time. Montanabw(talk) 07:11, 23 September 2007 (UTC)
- Well, well. So it is in history textbooks. And here I never knew historians were experts on genetics. Seems to me that if anything, you just eloquently demonstrated why that shouldn't be here in the first place, unless explicitely labelled as unverified rumour. 126.96.36.199 (talk) 19:36, 17 August 2008 (UTC)
If there is doubt that Charles II's negative traits resulted from inbreeding, perhaps this article will help: "Inbreeding Was Major Cause Of Fall Of Spanish Habsburg Dynasty". The original peer-reviewed article by Alvarez, Ceballos, and Quinteiro can be found here. According to this research, Charles II had an inbreeding coefficient of 0.254. This study has been widely referenced since its publication in PLoS ONE in April 2009. Articles citing Alvarez's team's research include those provided by HealthDay and the AFP. KAPet (talk) 22:12, 25 July 2009 (UTC)
- And once again, the problem of confounding correlation with causation slips into this article. The study authors explicitly acknowledge that their attribution of Don Carlos II's defects to two genetic factors is speculation, based on what kinds of genes are now known to produce the symptoms which contemporaries attributed to Carlos II. The authors' projections cannot be substantiated without genetic examination of the corpse (preserved in the Escorial, access to which is at the pleasure of Carlos II's current successor, King Juan Carlos I of Spain -- so it's not as if the task were impossible, thus arguably justifying supposition. The relevant research simply hasn't been undertaken). Keep it out of the article! Lethiere (talk) 09:23, 2 September 2009 (UTC)
Does anyone have a real source for the following info? Sounds kinda bogus and the reference is pretty old. WLU 14:06, 17 April 2007 (UTC)
- Cases involving people of the Mormon faith, (who practice polygamy) who have for generations bred with their direct relatives, (i.e. Mother to son union resulting in a daughter who later has a child by her father/brother) have resulted in cases of a rare disorder known as Throemboangiities Obliterians. Children born with this genetic disorder have deep recessed eye sockets, large protruding foreheads, and in many cases never develop teeth.<ref>UNIVERSA MEDICINA, 1899, p.295</ref>
- You should really do your research before deleting content. I did and found Throemboangiities Obliterians to be a real and bona fide medical disorder resulting from inbreeding of Mormon polygamists. Just simply typing something into "Google" and receiving no results, then saying "Shit, this must be fake" shows a lack of research ability. Shame on you, your the kind of person who makes Wikipedia inaccurate and watered down.
Your change was reverted, as you failed to provide any actual reference. You have not addressed my comments, all you did was revert a change then claim evidence. It's people like you that give anonymous contributors a bad name. WLU 23:49, 20 April 2007 (UTC)
- Agree with WLU. It is up to the anon editor to produce a reference for what on the face of it is an outrageous claim. --Michael Johnson 00:21, 21 April 2007 (UTC)
Didn't find anything about Throemboangiities Obliterians but if 'anonymous editor' (or anyone else) wants to add it, I found a source on Reuters today for fumarese deficiency being linked to FLDS (old-school Mormon) inbreeding in Arizona:  Happy editing! CanadianMist 15:05, 14 June 2007 (UTC)
Should we just merge this into the inbreeding article? Unless we get up around 30KB or it becomes disproportionately long, it would be better kept here. Richard001 07:11, 1 May 2007 (UTC)
- I'd say merge, it'd give us an excuse to trim down this article. WLU 16:54, 2 May 2007 (UTC)
I changed the entry on her in the royalty/nobility section, but there wasn't room to explain why in the summary. This is how the bulk of it read:
"Not only this, but all members of the Ptolemaic dynasty from Ptolemy II on engaged in inbreeding among brothers and sisters, so as to keep the Ptolemaic blood "pure". This was often looked over, or even made more complex when Ptolemies married other Ptolemies who had only a remote connection to the Ptolemaic bloodline (Cleopatra herself was the daughter of a Mithridatid princess)."
Firstly, in general only the kings were permitted to marry, so I changed "members" to "rulers". Secondly, although attempting to trace Ptolemaic bloodlines can make your head explode I don't recall anyone marrying a relative who could even charitably be described as "remote". Thirdly and most importantly, we don't actually know for sure who Cleopatra's mother was. There are several leading candidates, but no Mithridatids among them that I recall. So I deleted the last sentence as it seemed to be making some doubtful assertions. Finally, or actually firstly, I added her regnal number VII. I'm not sure about that, as to people not interested in Egyptian history of the period there was only ever one Cleopatra, and the numeral might actually make people think that someone else is being referred to. Perhaps it should go, but I can't decide.
188.8.131.52 16:45, 18 September 2007 (UTC)
- The "Cleopatra VII" thing made me do a bit of a double take, I actually assumed "the" Cleopatra was the one in question, but the number gave me a bit of pause. I'd suggest changing it back to simply "Cleopatra" as this is unlikely to cause confusion about which Cleopatra is being referenced, whereas "Cleopatra VII" is likely to be confusing to those not knowing an extraordinary amount about her. I assume there's an "established naming convention" by some WP or another saying the VII should be used regardless of whether it makes any sense. Sc00baSteve (talk) 07:45, 26 November 2008 (UTC)
- I'm not sure if the numeral will confuse people. If a reader is unsure of which Cleopatra the article is referencing, he or she could always, y'know, click on the link and read the article. If most people don't actually use provided article links, though, using just "Cleopatra" will bring the proper Cleopatra to mind for those unfamiliar with Egyptian history, and those who are interested can discover her regnal number by clicking on the provided link. KAPet (talk) 22:37, 25 July 2009 (UTC)
Distinction from "Royalty and Nobility"
Please correct me if I'm wrong, but doesn't Cleopatra also fall under the category of "royalty and nobility?" Why, then, does Ancient Egypt appear as a separate section from Royalty and Nobility? Would it be more accurate to make Royalty and Nobility a section header, with Ancient Egypt and Europe being sub-sections? KAPet (talk) 22:37, 25 July 2009 (UTC)
information available for use in this article
The text in the collapse box below was moved here from the article on incest. It's off-topic and overly detailed for that page, but it might fit in this topic well. It needs copyediting and further sources, but maybe it will be useful if anyone wants to merge it in to this article. --Jack-A-Roe (talk) 04:55, 28 March 2008 (UTC)
|inbreeding - text for optional merge into article|
Presumably because of the genetic harm done, animals inbreed only in extremely unusual circumstances: major population bottlenecks and forced artificial selection by animal husbandry. Pusey & Worf (1996) and Penn & Potts (1999) both found evidence that some species possess evolved psychological aversions to inbreeding, via kin-recognition heuristics.
Inbreeding leads to an increase in homozygosity (the same allele at the same locus on both members of a chromosome pair). This occurs because close relatives are much more likely to share the same alleles than unrelated individuals. This is especially important for recessive alleles that happen to be deleterious, which are harmless and inactive in a heterozygous pairing but, when homozygous, can cause serious developmental defects. Such offspring have a much higher chance of death before reaching the age of reproduction, leading to what biologists call inbreeding depression, a measurable decrease in fitness due to inbreeding among populations with deleterious recessives. Recessive genes, which can contain various genetic problems, appear more often in the offspring of procreative couplings whose members both have the same gene. For example, the child of persons who are both hemophiliac has a nearly 100% chance of having hemophilia.
Leavitt has argued that inbreeding in small populations can have long-term positive effects: "small inbreeding populations, while initially increasing their chances for harmful homozygotic recessive pairings on a locus, will quickly eliminate such genes from their breeding pools, thus reducing their genetic loads" (Leavitt, 1990, p. 974). However, other specialists have argued that these positive long-term effects of inbreeding are almost always unrealized because the short-term fitness depression is enough for selection to discourage it. In order for such a "purification" to work, the offspring of close mate pairings must be either homozygous-dominant (completely free of bad genes) or -recessive (will die before reproducing). If there are heterozygous offspring, they will be able to transmit the defective genes without themselves feeling any effects. This model does not account for multiple deleterious recessives (most people have more than one) and multi-locus gene linkages. The introduction of mutations negates the weeding out of bad genes, and evidence exists that homozygous individuals are often more at risk to pathogenic predation. Because of these complications, it is extremely difficult to overcome the initial spike in fitness penalties incurred by inbreeding (Moore, 1992; Uhlmann, 1992).
Recent research shows that couples consisting of third cousins actually have the highest level of reproductive success: "The results of the exhaustive study are constant throughout the generations analyzed. Women born between 1800 and 1824 who mated with a third cousin had significantly more children and grandchildren (4.04 and 9.17, respectively) than women who mated with someone no closer than an eighth cousin (3.34 and 7.31). Those proportions held up among women born more than a century later when couples were, on average, having fewer children." It is hypothesized that third-cousin couples may represent a "point of balance between the competing advantages and disadvantages of inbreeding and outbreeding."
The genetic risks of inbreeding are often overstated. "[F]irst cousins are third-degree relatives, uncle/niece are second-degree, and sibling/sibling or parent/child are first-degree. 'Uncle/niece risk is somewhat higher than first-cousin risk, which is between 1.7% to 2.8% above the background risk,' said [Robin] Bennett [manager of the Genetic Medicine Clinic at the University of Washington Medical Center]. 'Risk in first-degree relations is 7% to 31% - based on limited studies,' she said. Following Bennett's reasoning, the genetic risk of morbidity (the relative incidence of disease) in uncle/niece relationships is somewhere between 2.8% and 7% above the risk of unrelated couples." This risk is lower than the risk associated with becoming a mother when at or over the age of 47, something that can be legally done everywhere.
Father-daughter inbreeding as reproductive strategy
Mathematically, what are the merits of father-daughter inbreeding as a strategy for maximum propagation of the father's genes? The progeny of any such union would tend to have 75% of the genes of the father. So, let us assume that there is a certain cost to producing one child (e.g. opportunity cost, costs related to feeding/other upkeep of child, etc.). Let us take two possible scenarios. In both of them, we will presume that the father has already, with an unrelated mate, produced a daughter. In scenario 1, the father again reproduces with an unrelated mate, and his daughter reproduces with an unrelated mate. In scenario 2, the father reproduces with his daughter. For the purposes of this analysis, negative social and legal repercussions are ignored.
- Result = Two individuals with 50% of the father's genes
- Result = One individual with 50% of the father's genes, and one individual with 75% of the father's genes
But I suspect there are many other factors here which have not been accounted for, such as the fact that in scenario 1, it is the unrelated mate of the daughter who is likely providing the child's support; which he has an incentive to do, because that child has 50% of his genes. Then there are the age-related fertility aspects which I believe were at one time discussed at ephebophilia. Then there are the potential problems related to inbreeding and recessive genes. Has anyone else done analyses on this subject? Aldrich Hanssen (talk) 15:11, 27 July 2008 (UTC)
- You may wish to move this question to either inbreeding or consanguinity. You would probably get a better discussion in those areas.
- "Incest" is frequently misinterpreted of the de facto act of sexuality with close relatives, but that is incorrect. It technically means a sexual act that is immoral because it is with close relatives (hence the word root "unchaste"). In a hypothetical nation where marriage of father and daughter or brother and sister is legal and non-taboo, such actions are not "incest."Legitimus (talk) 15:29, 27 July 2008 (UTC)
- What is the purpose of this discussion? How would it improve the article? Is this some notable view? from a reliable source? Slrubenstein | Talk 19:48, 27 July 2008 (UTC)
- Wikipedia is not the place for original research (see WP:NOR) - thee is no point in discussing something unless it will have bearing on an actual improvement to the article, which means compliance with Wp:NPOV, WP:V and WP:RS. Slrubenstein | Talk 09:56, 31 July 2008 (UTC)
Ancient Egypt section inconsistencies
Some Egyptian Pharaohs married their sisters; in such cases a special combination between endogamy and polygamy is found. Normally the son of the old ruler and the old ruler's oldest (half-)sister became the new ruler. (emphasis added)
The old Pharaoh's sister would be his son's aunt, not his sister. I assume this is supposed to indicate that the new queen would be the new king's eldest "(half-)sister", the old king's eldest daughter. Those could be different women though, and I've no idea which is the operative relationship. I've edited the text assuming the father/daughter relationship, rather than the brother/sister, determined succession. I've also changed the "(half-)sister" stuff to clearly allow for both half- and full-siblings, as the text as written seemed to suggest (though somewhat unclearly) that we're talking about half-siblings at in certain (but not all) cases.
Someone with more knowledge in the area should look my changes over to ensure I got it right, though. It's now self-consistent and unambiguous, but I'm not sure it's correct Sc00baSteve (talk) 07:45, 26 November 2008 (UTC)
- I'm not sure, but it looks to me like the text is suggesting that the New Ruler would marry both his sister and his aunt, satisfying both the endogamy and polygamy parts of the equation. Der Elbenkoenig (talk) 03:35, 4 October 2011 (UTC)
Genetic Diversity in a population
I'm hoping someone who reads this article knows something about inbreeding. My question is how large must a population be to finally grow out of having to reproduce closely? I.E. an island of six animals will soon result in inbreeding, but a million will never have to. Where's the point at which genetic diversity becomes indefinite? 184.108.40.206 (talk) 08:16, 30 November 2008 (UTC)
If one starts at one persons generation (the life of a single said individual) as beginning at 1950, and takes 25 years back in time for every subsequent generation (most often, especially in times past, generations began younger / in less time, than that) it would be the year 700CE at fifty generations back, and the person born in 1950 would have 1,125,899,906,842,620 ancestors(!). That is, over a quadrillion, and only by the year 700 (not going back any further). This goes to show how inbred the human race is, and, all pairing off and producing dual-sexes species are. Because there were many less humans alive at once at that time than now even, and only fewer the further back in time one traces. 220.127.116.11 (talk) 11:48, 6 December 2008 (UTC)
The text about inbreeding in humans contains a contradiction. The second list consists of two paragraphs claiming different things about the Inca Empire. The first says that the sacred rulers occasionally married their sisters. The second one says that they used to marry their sisters with eventually disastrous results. Which one is correct?
- I agree that those statements seem incongruous. I also think that the Inca statements need to cite specific examples of inbreeding couples, and could really use a few references for verification. Additionally, I think their position under the Royalty and Nobility section (which, at the moment, seems to only be referring to royalty and nobility in Europe) should be rethought. Given the current organization of Inbreeding/Humans sub-sections, that the Inca examples should be placed within a South America sub-section. KAPet (talk) 23:04, 25 July 2009 (UTC)
The article mentions that unfit individuals can be culled, but it does not state why. The reason is that doing so removes deleterious alleles. This is worth mentioning. Also worth mentioning is that inbreeding, through the removing of deleterious alleles, can be methodically used to purge genomes of those alleles. This means thats inbreeding is not always associated with decreased fitness. Mention of these facts would greatly better the article. GreySun (talk) 15:58, 26 May 2009 (UTC)
I am considering adding info to the article:
"== Genetic purging == Inbreeding can be associated with increased fitness. This requires culling, or selection. When deleterious alleles are removed from a genome through selection, the deleterious effects of those alleles are removed. This contributes to the fitness of the resultant population. This technique is used in, but is not limited to, the making of heterotic hybrids."
"== Allele exposure == Inbreeding allows the expression of what otherwise may be unexpressed, recessive alleles. This can increase the variety of traits a population has. Since normally mutations are recessive, the exposure of alles that inbreeding produces may lead to evolution."
These two items may not be perfect, but I believe they have merit. If they are undesirable, they can be changed. If anyone wishes to comment or suggest changes to these possible additions, that would be appreciated. I will be checking back. Thanks. GreySun (talk) 16:35, 26 May 2009 (UTC)
This entry interprets a study of the Icelandic population as being indicative that minimal relation is optimal for health. I take exception to this interpretation. If the research does say third cousin relationships are most optimal, that is a far cry from saying that such relationships are most distanced of all human relations, which is the context with which we are dealing. GreySun (talk) 12:00, 19 July 2009 (UTC)
I edited the introduction and added the entries on Allele exposure and Evolution. If there are any disagreements with these edits, please say so here and why. Thanks. GreySun (talk) 12:45, 19 July 2009 (UTC)
Other Notable Cases of Human Inbreeding?
Could we add a section or link to a new article about notable cases of inbreeding in the human population outside of nobility?
The article on incest contains a link to the ignoble Goler clan as an example of incest (and, in this case, inbreeding, as well), but all other historical examples in the article concern either nobility or otherwise elite persons. Inbreeding contains no linked examples of human inbreeding beyond royal families.
I know there are more notable examples of non-noble inbreeding out there. I think this article could be improved by the addition of such notable examples because it would give the reader tangible evidence that inbreeding is not restricted to royal families, though instances of incest and inbreeding among royal families may have been tolerated (if begrudgingly) more than instances among the general population (see Roman Emperors Claudius and Caligula for examples). Though inbreeding amongst nobility may be more common than in the general public, I do not think non-noble cases should be excluded on these grounds. It could be argued that cases pertaining to average citizens, being less common, are all the more noteworthy. KAPet (talk) 21:11, 25 July 2009 (UTC)
Suggestions on Finding Notable Ignoble Cases of Inbreeding
Cases of inbreeding concerning the general public would likely be those with criminal significance, as in the case of Chiyo Aizawa, because such cases would need to be notable without involving elite persons. The subjects involved in these cases would probably be known and considered notable because of the instance(s) of inbreeding and related incidents (such as murder or rape), and not other reasons.
Inbreeding in Ancient Egypt was widespread
In the incest article is says in Etymology which is under History: “It is generally accepted that incestuous marriages were widespread at least during the Graeco-Roman period of Egyptian history. Numerous papyri and the Roman census declarations attest to many husbands and wives being brother and sister. Some of these incestuous relationships were in the royal family, especially the Ptolemies". Shod it not say something about that too?--Lord Don-Jam (talk) 14:09, 6 September 2009 (UTC)
Please fix this sentence
In the section "Isolated groups", the following sentence makes no sense. Please fix:
Among genetic populations that are isolated, opportunities for exogamy are reduced, however may not intend to inbreed.
This is new science theory which requires an acceptance of evolution.
Population explosions favour the individual that can inbreed and produce the most children. Natural defenses to inbreeding are blown through and lost, namely the appearance of an inbred (slanty eyes, etc.) can go unperceived or lost. People can fail to perceive the existence of overpopulation inbreeding also because to perceive it is dangerous to their existence if they are an overpopulation inbred. It is really quite simple to show its existence:
The number of offspring we have and mating style is inheirited.
The one with the most offspring quickly outnumbers all other "contestants".
To reacquire the characteristic to have the most children inbreeding is necessary.
Previous genetic models donot realize the consequences of the fact that the genes for inheiritance are inheirited.
I would add the current overpopulation inbreeding in humans is an atrocity, or natural catastrophe, in my opinion. It is easier to perceive this with other invasive species.
Without understanding overpopulation inbreeding, one looks at an invasive population of rabbits that is inbred and assumes the original number of rabbits was small. According to the theory, this is not necessarily the case. Even populations with large diversity become inbred when they expand.
The "Adam and Eve" myth observes the general human condition as inbred in Egypt, and assumes a single common ancestral couple. However, overpopulation inbreeding theory means that a large non-inbred gene pool was nontheless responsible for the inbred population. The Bible was a failed attempt to rationalize overpopulation inbreeding in other ways, with discussions of flood bottlenecks, phaoraohs and overacheivers who might have had huge families.
Insofar as kings are historically noted to be inbred, it may be the case that since the kings' subjects are inbred and reject dissimilarities, that the kings claim inbred status also to maintain popularity, without actually being inbred. They may also mistakenly become inbred on observing that their populations are prolific inbreds.
What are the features of the overpopulation inbred? For instance, the ability of the overpopulation inbred to combine it numbers to exclude and destroy its genetic competitors in its own species. (eg. rioting, mass exclusion, mass overpresence, mass harrassment, gang assault, mass common deceit, mass common presumption, war...) Its tendancy to acquire a genetic trait which easily identifies itself to others of its type, for example skin colour. This speeds its growth and quickly lowers its genetic variation as it can then easily identify the route to inbreeding and quickest growth.
Overpopulation inbreds descended from a larger genetic pool are potentially more invasive and insidious because they have a larger selection of ganging features to draw from.
How is it possible that defenses to inbreeding would ever be "blown"? They may be blown by an invasive species which has not been an invasive species before and suffered for it. In primates, small groups of animals are the rule. In their ancestral history there have been no very large population explosions recently except protohumans. When opportunity came for man to leave Africa and explode in numbers the genome would have been thinned as the population moved east across Asia, or as rare mutations were chosen from among the Africans to handle the different climate. Then it could acquire adaptations which would cause its inbreeding defenses to fail, following the acquisition of the agricultural lifestyle for instance. The population would no longer be individuals who knew everyone in their mating group, how many children each family had, and who everyone was related to. The memory of the species was strained beyond its capacity. Inbreeding errors occured more frequently, and adaptations arose to overpower inbreeding defenses, as there was evolutionary pressure to inbreed. "Survival of the fittest" is no longer what occurs in such a situation. Potentially, fitter variations cannot rise for extreme lengths of time if ever, because the population must first lose its tendency to suppress variation. Hence the general stagnation of species. (This paragraph does not imply Europeans and Africans are not also overpopulation inbred. Currently any human group over 500 or so in number is inbred and the overwhelming majority that are only that size too. Aboriginals including Africans are measured to be the least inbred with DNA sampling. However, missing hair is a symptom of inbreeding in mammals, and the legendary Yeti or Bigfoot may be the only humans that are not inbred compared to other species of animals. The chimpanzee has 10 times the genetic variation of man, so you can't talk about human beings without talking about inbreeding.)
Overpopulation inbred populations are not necessarily completely inbred, but have some genes which are completely inbred. The inbreeding is pushed to the maximum viable extent even after actual numbers have hit the environmental limit. The population does not "bottleneck".
I have contacted the CDC and Health Canada with a crisis warning on the predictions of this theory (ie. widespread human inbreeding depression tending to a complete majority inbred population). Also, there is a new syndrome here, to coin a term: "Inbred Overpopulator Syndrome". — Preceding unsigned comment added by GuildCompounder (talk • contribs) 01:56, 8 February 2011 (UTC)
Tests for Inbreeding
There should be something in this article on inbreeding testing, human and otherwise. In the meantime, search in the internet including terms like "homozygosity" and "genotypic homozygosity".—Preceding unsigned comment added by 18.104.22.168 (talk) 20:40, 14 February 2011 (UTC)
This article and the cheetah article is at odds as to what caused the low genetic variability in cheetahs. The cheetah article states it's an ice age, the inbreeding article says it was humans. Both cite sources (which I havn't examined) but I think the ice age theory is the concensus today.
Citation from the cheetah article:
The cheetah has unusually low genetic variability and a very low sperm count and motility, and deformed flagella.[...]It is thought that the species went through a prolonged period of inbreeding following a genetic bottleneck during the last ice age.
- The Cheetah article says that a genetic bottleneck occurred during the last ice age, not that the ice age caused the bottleneck. It cites a supporting source to which I don't have access. This article cites two supporting sources, one of which says that genetic research supports a hypothesis of an ancient Pleistocene bottleneck (which that WP article says spans the world's recent period of repeated glaciations).. The other cited supporting source links to an archived copy which isn't currently available -- I don't know whether or not that source supports this article's assertions about causes of the bottleneck. Wtmitchell (talk) (earlier Boracay Bill) 07:40, 17 March 2011 (UTC)
- Charles Darwin, through numerous experiments, was one of the first scientists to demonstrate the effects of inbreeding depression. Darwin had married his first cousin, Emma Wedgwood and their grandparents had been first cousins. He later became concerned that inbreeding within his own family would adversely affect the health of his own children. The Darwins had ten children, but three died before the age of ten. Of the surviving children, three of the six who had long-term marriages did not have any children.
"The reduced genetic diversity that results from inbreeding may mean a species may not be able to adapt to changes in environmental conditions."
This needs to be edited and changed to "The reduced genetic diversity that results from inbreeding [in a reproductively isolated subgroup] may mean [that subgroup] may not be able to adapt to changes in environmental conditions."
I have no formal training in such calculations, but the coancestry of a parent-offspring pairing should surely be 1/2, not 1/4 as stated. The rest of the statistics have to be changed to represent this. I think somebody might have gotten confused and written something to do with the difference in variance between sibling-sibling and parent offspring pairing. Could somebody with a bit of background in mathematical biology and more confidence in their math than I maybe write those in? — Preceding unsigned comment added by 22.214.171.124 (talk) 13:07, 14 November 2013 (UTC)
Ways to improve: 1. More examples 2. Elaborate more on how to measure inbreeding 3. Mentions effects of outbreeding after inbreeding, but not anything about crossbreeding — Preceding unsigned comment added by Abraham.135 (talk • contribs) 23:47, 30 September 2014 (UTC)
Artifical Insemination (AI) has been helping farmers with their animals where they can select what kind of offspring they want produced. I wonder how this can help with inbreeding by collecting different samples and then freeze them and use them when a population may be getting inbred so new genes can be introduced and then a whole population won't be affected. AI could possibly help with animals that are becoming endangered or threateded and have samples in lab that could be used to help endangered animals from being inbred.Medford.6 (talk) 16:32, 1 October 2014 (UTC)
There is some uncertainty as to what extent the pharaohs actually married their sisters. The Ancient Egyptian word for sister and wife were spelled the same. So unless the queen's parents have been mentioned in writing we don't really know if a pharaoh was married to his sister. Also, humans suffer the adverse effects of inbreeding more easily than other mammals. Even less degrees of inbreeding than brother-sister incest often results in sterility. For this reason marrying your sibling or half-sibling generation after generation simply does not work. After a couple of generations of such severe inbreeding all sons were probably sterile. If they pharaohs really married their sisters or half-sisters generation after generation a considerable part of them would have either lacked heirs or been succeeded by their nephews rather than their sons.
2015-01-12 Lena Synnerholm, Märsta, Sweden.
- "When Incest Is Best: Kissing Cousins Have More Kin - Scientific American, February 8, 2008".
- "Curtain drops on incest drama - The Register Herald, January 6, 2005".
- "Maternal Age and Chromosomal Abnormalities at Live Birth".
- O'Brien, S., D. Wildt, M. Bush (1986). "The Cheetah in Genetic Peril". Scientific American 254: 68–76.
- Berra et al. (2010). "Was the Darwin/Wedgwood Dynasty Adversely Affected by Consanguinity?". doi:10.1525/bio.2010.60.5.7.
- "Inbreeding May Have Caused Darwin Family Ills, Study Suggests". Science Daily.