Talk:Human evolution

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6% figure

I note a contradiction between the primary record and the secondary press reports involving the proportional representation of Neanderthal and Denisova DNA. The abstract of the first Reich nature paper does in fact say that 6% of Denisova DNA is present in Melanisians. However, every secondary report I see of the paper says that 6% of Melanisian DNA is Denisovan. Admittedly a subtle difference but a difference. Unfortunately, I don't have access to the whole Reich paper right now to see how it is phrased in the body, but every other reference I see is the other way around. This ([1]) summary of the second Reich paper is also talking about proportion of different groups of Melanisians that is Denisovan, and not the other way around. Can anyone help with this? Agricolae (talk) 22:07, 11 November 2011 (UTC)

Any of these help?

• Denisova Admixture and the First Modern Human Dispersals into Southeast Asia and Oceania
• The Shaping of Modern Human Immune Systems by Multiregional Admixture with Archaic Humans
• Genetic history of an archaic hominin group from Denisova Cave in Siberia Slartibartfastibast (talk) 07:12, 23 December 2011 (UTC)

Some VERY recent human evolution.

In your more affluent countries, the age at which children go through puberty continues to decrease steadily. I am greatly surprised that this comment did not come up a long time ago in this article - this is a high-profile concern and totally verifiable.

The rest are all unsourced, hence only put here, on the discussion page.

• Also in more affluent countries, children are able to produce the various enzymes that digest milk, up to an age of several years. In the 20th century, children stopped being able to produce these enzymes well before they reached the age of two years.

Excuse me, I have to say this is completely untrue, at least of European children. As far as I'm aware, the capacity to digest milk is present throughout life in all human populations where domestic cattle have been used for the provision of milk for a long period of time. What's more, this is a well-known textbook fact. Macdonald-ross (talk) 14:17, 19 December 2011 (UTC)

Maybe I didn't phrase that very well. We lose the capability to digest SOME parts of cow's milk at a very early, but increasing age. Even in Europe and other places where cows milk is prevalent. Old_Wombat (talk) 07:33, 23 December 2011 (UTC) Here you go, someone below very kindly found the exact article: Lactase persistence. Old_Wombat (talk) 07:42, 23 December 2011 (UTC)

• The size of the human jawbone, particularly the lower jawbone, has become slightly but significantly smaller. This is a problem because the number and size of teeth has stayed the same.

Old_Wombat (talk) 10:12, 23 November 2011 (UTC)

We would need a source not only for the phenomena, but also indicating that they are genetic in nature before they could even be considered. Agricolae (talk) 15:10, 23 November 2011 (UTC)

Here you go: Dental Occlusion in a Split Amazon Indigenous Population: Genetics Prevails over Environment

• Studies examining human and nonhuman primates have supported the hypothesis that the recent increase in the occurrence of misalignment of teeth and/or incorrect relation of dental arches, named dental malocclusion, is mainly attributed to the availability of a more processed diet and the reduced need for powerful masticatory action. [...] Our findings downplay the widespread influence of tooth wear, a direct evidence of what an individual ate in the past, on occlusal variation of living human populations. They also suggest that genetics plays the most important role on dental malocclusion etiology. Slartibartfastibast (talk) 06:38, 23 December 2011 (UTC)

By the way, there are some recent documented examples. See, for instance, Perry et al, "Diet and the evolution of human amylase gene copy number variation", Nat Genet. 2007 Oct;39(10):1256-60. Agricolae (talk) 17:17, 24 November 2011 (UTC)

Even if there's a gradual human evolution recently, the genomic diversity of humans is still small. Please keep that in mind. Komitsuki (talk) 11:33, 11 December 2011 (UTC)

That's nonsense, because the genomic difference between humans and chimps is also very small. It's not about quantity, but quality.--Kmaga (talk) 16:11, 11 December 2011 (UTC)

• These are correct examples, just not really of evolution. The size of the jawbone characterizes European populations - but there's no evidence that this is under selection. The question of falling menarche is not about evolution at all - evolution can't work quickly enough to let the arge of Menarche drop from 16 to 13 in three generations. This is simply a question of environemental changes acting on the onset of menarche - the female body is evolutionarily programmed to go into menarche early if it is well nourished and late if it is not. BTW: I reccommend Wenda Trevathan's Ancient Bodies modern lives for treatment of the menarche changes, and other ways in which evolutionary principles can motivate fruitful inquiry into health issues.·ʍaunus·snunɐw· 16:16, 11 December 2011 (UTC)

So for an actual example of current human evolution (or at least of ongoing natural selection, as opposed to mere differing appearances under differing nutrition/environment) you could look in malaria-prone areas at the distribution of sickle cell anaemia genotypes. It has trivially been shown quantitatively that the hybrid is being selected for. Cesiumfrog (talk) 22:14, 11 December 2011 (UTC)

Another example is lactase persistance.·ʍaunus·snunɐw· 22:22, 11 December 2011 (UTC)

Or rather examples, as the mutation responsible in Eurasia is separate from that in Africa, and the expansion in each population dates from the approximate time of the introduction of cattle herding in those population. Basically, nature replicated the experiment. Agricolae (talk) 22:38, 11 December 2011 (UTC)

Relevant:Cultural diversification promotes rapid phenotypic evolution in Xavánte Indians (Accessible mirror)

• Shifts in social structure and cultural practices can potentially promote unusual combinations of allele frequencies that drive the evolution of genetic and phenotypic novelties during human evolution. These cultural practices act in combination with geographical and linguistic barriers and can promote faster evolutionary changes shaped by gene–culture interactions. However, specific cases indicative of this interaction are scarce. Here we show that quantitative genetic parameters obtained from cephalometric data taken on 1,203 individuals analyzed in combination with genetic, climatic, social, and life-history data belonging to six South Amerindian populations are compatible with a scenario of rapid genetic and phenotypic evolution, probably mediated by cultural shifts. We found that the Xavánte experienced a remarkable pace of evolution: the rate of morphological change is far greater than expected for its time of split from their sister group, the Kayapó, which occurred around 1,500 y ago. We also suggest that this rapid differentiation was possible because of strong social-organization differences. Our results demonstrate how human groups deriving from a recent common ancestor can experience variable paces of phenotypic divergence, probably as a response to different cultural or social determinants. We suggest that assembling composite databases involving cultural and biological data will be of key importance to unravel cases of evolution modulated by the cultural environment.

From a Discover Magazine genetics blog post about the article:

• The authors used a set of variables amongst groups of indigenous Amazonian populations, and analyzed how the variables related to each other. In particular, they found that one tribe seems to have undergone a great deal of phenotypic divergence from a genetically and linguistically related population (last common ancestors ~1,500 years B.P.). The phenotypic variables were head circumference, facial height, nasal height, nasal breadth, and glabello-occipital length. They also constructed a phylogeny using mtDNA, and related that and the phenotype to geography, and climatic 6 × 6 distance matrix. One assumes that variables like phylogeny, geography and climate should be robust predictors of phenotypic divergence (i.e., in a random drift model phenotypic divergence would be proportional to genetic distance).

Slartibartfastibast (talk) 06:49, 23 December 2011 (UTC)

Wow, what a discussion, I hadn't intended to generate so much controversy. I'd like to move forward. Here is a suggested addition to the section on "Recent and current human evolution". We can now debate something more concrete. So here we go:

There has been some evidence of human evolution in time spans as short as decades. For example, Lactase persistence, changes in the shape and size of the human jawbone, (please add others).

Please attack this as you see fit. Old_Wombat (talk) 07:41, 23 December 2011 (UTC)

One problem is that these are examples of adaptation, and may or may not lead to evolution (if we are allowed to distinguish between the two terms). Dbfirs 21:00, 1 January 2012 (UTC)

No. The word evolution is right there in the title:

• Cultural diversification promotes rapid phenotypic evolution in Xavánte Indians

Also:

• Evidence for evolution in response to natural selection in a contemporary human population (March 2011)

Slartibartfastibast (talk) 15:20, 2 January 2012 (UTC)

• NYT: Genome Study Points to Adaptation in Early African-Americans (Jan 2, 2012)

"Researchers scanning the genomes of African-Americans say they see evidence of natural selection as their ancestors adapted to the harsh conditions of their new environment in America." — Preceding unsigned comment added by Slartibartfastibast (talk • contribs) 03:18, 5 January 2012 (UTC)

Yes, I agree that your examples sound more like genuine evolution, but "evolution in time spans as short as decades"? No way! Dbfirs 07:48, 5 January 2012 (UTC)

Yes way.Slartibartfastibast (talk) 13:44, 8 January 2012 (UTC)

Out of Date tag

I see no discussion about how the article is supposedly out of date, I say we remove it. THoughts? Dbrodbeck (talk) 12:35, 22 December 2011 (UTC)

You can search it out above. A particular example was that the article presents the impression that there are currently two main but conflicting hypotheses, fairly evenly matched in competition against one another, when in fact neither of those extreme views is held anymore. (Rather, both conflicting views have apparently been replaced with a new more-nuanced consensus.) As such the article is outdated. Cesiumfrog (talk) 01:05, 23 December 2011 (UTC)

I see one anonymous IP and several others disagreeing, perhaps I am missing something. 03:57, 23 December 2011 (UTC)

Why does "human evolution" only start with Homo

The article omits all of human evolution before the appearance of Genus homo. Surely human evolution starts with the divergence from the Great Apes, particularly from the Chimpanzee 5-6 million years ago. There is much excellent research done on this. John D. Croft (talk) 17:35, 31 December 2011 (UTC)

?? Human evolution#Before Homo.Moxy (talk) 20:26, 31 December 2011 (UTC)

I'm pretty sure we never diverged from great apes, I think we're still classified as one of them. KrisPwnz (talk) 19:13, 30 January 2012 (UTC)

Units error in discussion of energy usage of brain?

The snippet "The brain of a modern human consumes about 20 watts (400 kilocalories) per day..." looks wrong to me for the simple reason that watts and kilocalories have different physical dimensions, and therefore can not be equivalent. Perhaps what is meant is "... 20 watts (40 kilocalories per day) ...". Could someone verify this? --68.0.167.220 (talk) 06:00, 1 January 2012 (UTC)

I have posted a note at the Reference desk regarding your question. Rivertorch (talk) 06:51, 1 January 2012 (UTC)

Units mentioned are different, Watts and "kilocalories per day" are units of power, suitable for describing brain energy consumption. The 20 Watts average (same as just over 413 kilocalories per day I think) quoted seems realistic. Polypipe Wrangler (talk) 08:13, 1 January 2012 (UTC)

Using the calculator at UnitConversion.org I come out with 20 Watts = 412.7 kilocalories per day, which is very close to the stated figure (which is just an approximation anyway). Note it takes a bit of fiddling, as the units on the calculator don't exactly correspond to those given here. --jjron (talk) 08:25, 1 January 2012 (UTC)

You can verify on paper; the unit kilocalorie is described in our article. If you want a quick check, Wolfram Alpha can perform the conversion; Google can also perform unit conversions. Nimur (talk) 09:17, 1 January 2012 (UTC)

Thanks for all the help, folks, but it's clear the objection is to the nonsensical "Watts per day", not 40 vs. 400 - that's just a typo. ;) 66.57.57.178 (talk) 07:32, 9 January 2012 (UTC)

Yes Watts per day makes no sense. What was intended was 20 Watts (400 calories per day). edit:I also just noticed the figure does not have any citations. IRWolfie- (talk) 15:29, 1 January 2012 (UTC)

Fairly easy to find citations, though estimates vary, such as [2], [3](25 watts) , [4](10 watts) etc. Perhaps it depends on how hard you are thinking? Dbfirs 20:54, 1 January 2012 (UTC)

It would be good if some solid citations could be found, I don't think the sources are really that reliable. IRWolfie- (talk) 22:28, 9 January 2012 (UTC)

"All animals have a tail at one point in their development"

This affirmation is not backed up by reference 2, and is misleading. A sponge is an animal and certaily doesn't have a tail — Preceding unsigned comment added by 189.178.204.225 (talk) 06:35, 14 January 2012 (UTC)

I corrected it a while back (to all chordates ...), but someone undid all of my fixes. The page is back to being filled with garbage. — Preceding unsigned comment added by 24.94.234.96 (talk) 12:30, 3 February 2012 (UTC)

Humans never had tails

"Humans inherited their tail bone, a remnant of what was once a human tail, from primate ancestors"

That is wrong; humans never had tails. — Preceding unsigned comment added by 24.94.234.96 (talk) 12:34, 3 February 2012 (UTC)

All human embryos have a tail during weeks 13-14 of gestation.·ʍaunus·snunɐw· 16:50, 14 February 2012 (UTC)

And some are even born with them although fortunately not very many.Jobberone (talk) 10:28, 15 February 2012 (UTC)

The 'vitamin C' gene was disbled LONG before human evolution

"For example, humans have structures in their genetic make-up that were once used to produce enzymes (L-gulonolactone oxidase) to process vitamin C; many other animals have this functioning DNA, but at some point in human evolution a mutation disabled the gene, leaving behind its remnants as junk DNA."

That is wrong. Chimps also have the same pseudogene, and they aren't humans. In fact, it’s not just humans and chimps that share a GULO pseudogene with a primate-specific mutations: instead, all simian primates -- humans, chimps, gorillas, orangutans, gibbons, Old World monkeys, New World monkeys -- as well as tarsiers have the GULO pseudogene, — Preceding unsigned comment added by 24.94.234.96 (talk) 12:40, 3 February 2012 (UTC)

Do you have a reference? IRWolfie- (talk) 10:52, 24 February 2012 (UTC)

Embryonic evidence

Why is there no embryonic evidence for human evolution? Here are some, there are others.

1) Human embryos do not get their nutrition from yolk stored in a yolk sac, yet human embryos have a (vestigial) yolk sac. 2) In addition, the human genome contains VIT pseudogenes: now-disabled-by-mutations genes that are involved in yolk production. 3) Humans, despite not having a tail, develop a postanal tail in embryonic development. 4) Human embryos start off with a very fishlike arrangement of aortae and aortic arches, which then must undego much remodeling to finally end up in a human-appropriate arrangement. — Preceding unsigned comment added by 24.94.234.96 (talk) 12:45, 3 February 2012 (UTC)

There is a great deal of evidence in embryology. Check out any good textbook on developmental biology, comparative developmental biology or comparative embryology, yada.Jobberone (talk) 11:02, 15 February 2012 (UTC)

I think what he was talking about, Jobberone, was that there doesn't seem to be embryonic evidence for human evolution presented in the article, not that it doesn't exist at all. Cadiomals (talk) 16:35, 15 February 2012 (UTC)

How comprehensive do you think it should be? I've had several embryology courses as well as developmental biology and that's a big undertaking. Or do we just want to say there is evidence for evolution of phyla and man in our own embryology and put a couple of references in there with an embryology link?Jobberone (talk) —Preceding undated comment added 17:01, 15 February 2012 (UTC).

This page focuses on the evolution of hominids (humans). Of the examples, 1, 2, and 4 are all shared by all (at least most) mammals (there is an Evolution of mammals page), while 3 is common to all apes. This page just cannot be a repository for all of the evidence for the whole process of evolution that resulted in humans, or it would have to mention the presence of five digits, Your Inner Fish, and the commonalities between the human mitochondrial polymerase and those of bacterial. The page is not List of evidence that humans evolved. Agricolae (talk) 17:23, 15 February 2012 (UTC)

I agree that this isn't what the article is about. Any evidence presented in this article should be evidence that helped in accurately mapping the lineage of humans, not evidence that humans even evolved at all. I know what the underlying motive in that is. There is no need to try to satisfy or cater to the creationists here. We start with the assumption that humans evolved and go from there; we don't have to establish it here. Also, much of the evidence that humans evolved can be applied to many other groups of organisms, so its no use. Cadiomals (talk) 22:24, 15 February 2012 (UTC)

EDIT CONFLICT

I spent a great deal of time working on the introduction and adding refs to evidence for evolution. I was going to discuss this but I'd like for others to review the changes and help sort out any unwanted deletions.Jobberone (talk) 11:18, 14 February 2012 (UTC)

What the heck is with that million mile long line of citations in the evidence section??? Surely you didn't put that many cites for one single fact? it needs to be scattered. Cadiomals (talk) 11:25, 14 February 2012 (UTC)

If you read it, it states the following are references to both evolution and the evolution of man. If that is too extraordinary then let's find a better solution. But no it's not to reference one single fact. In fact I'll remove them for the time being.Jobberone (talk) 11:52, 14 February 2012 (UTC)

Well, that is the wrong way to cite sources. You don't put down paragraphs of information and then at the end say "here are all the cites" and put them all in a long line. Every statement of fact that may be challenged needs to have a citation immediately after it. You should check out WP:CITE if you haven't already. Cadiomals (talk) 16:39, 14 February 2012 (UTC)

It wasn't my intent to reference anything in particular and what I wrote was unlikely to be challenged since it was general knowledge. I was giving references to evolution and to evolution of man. However I agree it might be best not to address references to evolution here. People can easily go to the main article via evolution. I also believe we should consider removing the material about the plantaris muscle etc. I don't feel strongly about it. Is there a way to make a list of references and use a 'pointer' to view them? That way you can have a more extensive bibliography without creating such an eyesore.Jobberone (talk) 10:26, 15 February 2012 (UTC)

Will be redoing these section(s) that now have GUESS words and are very badly sourced. VERY bad source this isMoxy (talk) 17:27, 14 February 2012 (UTC)

Yeah to be honest WHY do we even have this section? I feel like the Evidence section only exists to try to convince any creationist readers who might be out there (who probably woouldn't read it and won't be convinced anyway). Either we remove it, merge the content with other sections or put in some more reliable sources. Cadiomals (talk) 18:41, 14 February 2012 (UTC)

I agree - most can be removed ... See what I can source.Moxy (talk) 04:34, 15 February 2012 (UTC)

A sentence says something different that what was meant.

I think that the sentence:

"and Neanderthals and other hominids, such as Denisova hominin may have contributed up to 6% of their genome to present-day humans.[13][14][15]"

should be reworded to say:

and Neanderthals and other hominids, such as Denisova hominin may have contributed up to 6% of the genome of present-day humans.[13][14][15]

67.142.162.24 (talk) 00:22, 27 February 2012 (UTC) Steve Stites

This has already been mentioned here once before without resolution (see "6% figure" section currently at the top of this talk page). The problem is that the secondary sources (press reports) say it one way (the way you suggest), while the abstract of the original paper says it the other. I have not been able to lay hands on the original paper to see whether the abstract or the press reports better reflect the language of the paper itself. Agricolae (talk) 02:02, 27 February 2012 (UTC)