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As a layperson, I find this article deficient of worthwhile information, because while it juxtaposes two examples of skulls which are clearly different, it says nothing about the variance in modern human brain shape. It doesn't seem interesting to me unless one were to characterize the variance and describe the ancient skull in terms of the modern distribution.
What's interesting that if the basic point is true (that modern human brains emerged only 100,000 - 35,000 years ago) then its amazing (and scary) how quickly things have moved from there. It wasn't that long after "relatively speaking" that the Greeks emerged, then the Romans, Egyptians, Europe, Asia, etc, and now our modern technology driven civilization.
Speed of evolutionary change is basically proportional to the population size. Thanks to the huge increase in population size after the rise of agriculture, more human evolution has happened in the last 5000 years than the previous 500,000.
Really? I thought selective pressure was required to cause a major shift in the average human. The reason that our population has boomed is because our selective pressure has declined significantly. Or are you more talking about the adaptability of the species overall has increased?
In a booming population, it seems to me that evolution can be more rapid in "selection" with less "pressure". For instance, if humans start exploring a new continent, some might have 10 times the normal number of grandchildren, and their genes would rapidly outnumber the others. Whereas if population is static, then you could say there's more "pressure" but there's probably less "selection", because there's less opportunity and variance in success.
Evolution acts on genetic diversity present in the population. The rate at which new genes (mutations) appear is basically a constant proportional to the population size (i.e. double the population and you double the rate new genes are formed). The rate at which new genes under positive selection spread through the population is approximantly equal to the log of the population size. This means it only taken 3x longer for a new gene to spread through a population of 100 million as it does to spread through a population of 1 million.

The end result is the bigger the population the more evolution even if in a static environment most of the evolution is invisible. Of course the environment of farmers is very different to hunter-gathers so there has been a large amount of visible evolution in the last 5000 years.

I think that depends on pressures and variation as well; without selection pressure I don't think that there is a reason why the variation in the overall population will change.
Selection pressure doesn't just mean people being killed by things. Some groups having significantly more surviving offspring is also a selective pressure.
There are still selection pressures, only they are more focused on sexual selection rather than survival selection. There still remain advantages to being smart healthy and athletic. What has changed is the lower bound on these required for survival. What has happened to pressures on these required for reproduction seems like a much harder to judge question.

Certainly though, those with advantageous mutations seem to have a better chance of reproduction.

I really wonder about the relations between the earlier hominides and the brainiacs.
How do they reconcile the fact that apparently only brains after 35k years ago show this new brain morphology when humans left Africa at least 70k years ago (when they showed up in Australia).

So one of the groups, either the "in Africa group" or the "out of Africa" group still should have the "old style brains" unless magically the changed happened in both groups at simultaneously. And yet I believe all humans currently alive have essentially similar brains.

It's uncomfortable to consider, but there is strong evidence to suggest that the brains of Australian aboriginal people differ in significant ways from their Caucasian bretheren. One study found the aboriginal visual cortex to be significantly larger than the Caucasian equivalent [0], possibly as an adaption to Australia's (visually) vast open spaces. The same study found the Caucasians had significantly larger parietal lobes and cerebellums - the same structures mentioned in this article. Another study found that Caucasians have significantly larger brains on average compared to those of aboriginals [1].

There's also evidence to suggest that modern humans from India [2] have contributed to the Australian gene pool for millennia (long before the arrival of the British), so more dramatic cranial differences may have already been averaged out.

EDIT: deleted figure mis-remembered from an unrelated study.

[0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1261675/ [1] https://www.ncbi.nlm.nih.gov/pubmed/6926391 [2] http://www.pnas.org/content/110/5/1803

Isn't gene expression dependent on environment though? Is there some reason to believe that these differences are inherent, and not the result of gene expression being affected by the environment?
IANA biologist. That said, if by "inherent" you mean primarily genetically determined, I'd say that explanation seems most likely given the evidence.
>primarily genetically determined

Even this statement isn't as absolute as you seem to think it is. Your genes may or may not express based on the environment in which you grow up. Primarily genetically determined doesn't make sense, since genes aren't working in a vacuum.

> Is there some reason to believe that these differences are inherent, and not the result of gene expression being affected by the environment?

That is a question that remains to be answered, and is only just beginning to be looked into through research on epigenetics[1].

[1] https://en.wikipedia.org/wiki/Epigenetics

If our brain structures were different (at least in so far as the organization or distribution of cells within the cranium and not the external measurement) then one would expect adopted children from places where brains are very different to perform differently then peers in new locations.

Yet I remember reading a study that showed that black children from Africa adopted by white parents in Germany performed at the same level as their peers. There have been other such studies with very similar conclusions.

It could also be that differences in academic performance (I'm assuming academic is the performance you were referring to in your comment) are not accurate metrics for identifying the effects of differential brain organization.

In scenarios like that, it's also difficult to control for the impact of different level of support for students in academic matters. For example, focused support for under-performing students compared to relatively relaxed support for students meeting expectations.

I could probably also see the impact of different psychological factors associated with being adopted by a family on a different continent being hard to control for.

My rambling brain confounded a few studies I had read.

My mistake. I was incorrect about the study being related to adoptions. It was actually something interesting that happened in Germany. I had read an environmental interpretation of the Eyferth Study: https://en.wikipedia.org/wiki/Eyferth_study

We better get this racism thing in check before we're literally dealing with different species of human (assuming that some groups of people remain isolated and we don't experience total global homogeneity in the future)
What do you mean by "get in check"? It's pretty well accepted that we deal differently with different species. We'll need to decide what counts as ethically acceptable, but blind insistence that "all humans are created equal" isn't going to fly when we have undeniably different species of human.
I mean racism needs to be obliterated before the differences our governments and world religions trick us into bickering about become even greater, and we regress on fair and ethical treatment of all people in both the eyes of the law and the heart of the common man.
I thought racism was defined as:

> prejudice, discrimination, or antagonism directed against someone of a different race based on the belief that one's own race is superior.

I completely agree that when looking at differences among population groups in a species, one should avoid normative statements such as "such and such makes this population superior," but is there harm caused by identifying differences in averages, medians, and variance in said defined population groups? In other words, if I am speaking about dogs, is it inappropriate to say chihuahuas are on average smaller than boxers and labs? Same species, but distinct populations.

I think that is at the heart of it. To be "colorblind" to both the historical and modern claims of specific population superiority in one dimension or another is misguided-bad claims made in good faith should be addressed head on, in requests for citations, evidence, etc. Similarly, to identify where differences may occur seems to be a reasonable action so long as there is recognition to cultural or historical drivers too, as GP implicitly identifies with the optical adaptation mentioned (though, TBH, I have not read the study he or she proffers and thus have no insight to the claim).

On one hand, we have Darwin, who straight up wrote a book about why some races are superior [0], and on the other hand we have extremists who take offense even at assessments like "Men are on average stronger than women."

For a modern-day Darwin, we have James Watson, the father of genetics, who has some interesting things to say [1]

[0] https://en.wikipedia.org/wiki/On_the_Origin_of_Species [1] https://en.wikipedia.org/wiki/James_Watson#Controversial_com...

James Watson definitely has a masculine, biased perspective, but I mostly consider him to be somewhere in the middle of the spectrum. Yet, his career has suffered greatly for his remarks dealing with race and genetics.

Personally, I think it is patronizing if not downright deceitful to pretend differences don't exist between isolated demographics, but it will remain a touchy subject for a long time and most scientists will see what happened to Watson and pursue other areas of research.

>Personally, I think it is patronizing if not downright deceitful to pretend differences don't exist between isolated demographics,

We don't have many isolated demographics (although there are some) both because pre-modern humans were capable of traveling over extremely long distances (i.e. isolation is unlikely) and because humans haven't been around for a particularly long time.

Unlike many species humans are surprisingly genetically similar to each other[0]. Some of this also results from the fact that humans may have passed through a very small genetic bottleneck 100,000 years ago in which the human population was reduced to around 3,000-10,000 people other studies dispute this but arrive at similar genetic conclusions [1].

>but it will remain a touchy subject for a long time and most scientists will see what happened to Watson and pursue other areas of research.

This isn't fair to scientists that legitimately engage in controversial topics. Watson is a bit of a crank, for example:

>'In a lecture hall jammed with more than 200 Berkeley students and faculty members, Watson showed a slide of sad-faced model Kate Moss to support his contention that thin people are unhappy and therefore more ambitious. "Whenever you interview fat people, you feel bad, because you know you're not going to hire them," Watson said."' [3]

That isn't a scientific conclusion. Much of the anger against Watson is that he says stupid unscientific things to support his own biases and then hides behind his discovery. This follows a pattern, which occurs across the political spectrum, in which a scientist who makes an important discovery thinks that discovery means everything they say is correct.

[0]: https://en.wikipedia.org/wiki/Human_genetic_variation

[1]: Population Bottlenecks and Pleistocene Human Evolution https://academic.oup.com/mbe/article/17/1/2/975516

[2]: http://www.sfgate.com/science/article/Nobel-Winner-s-Theorie...

I said Watson had a biased perspective.

I'm not trying to lay down any sort of narrative, I'm just presenting facts in a neutral light.

The quote you selected is found in the link I provided.

It is something we will have to grapple with. Cognitive genomics is already starting to confirm very politically incorrect things, such as the the confirmation of a dysgenic trend in Iceland, which has been implied from phenotypic data but career ending to acknowledge: https://www.gwern.net/docs/genetics/selection/2017-kong.pdf

This is the tip of the iceberg. Once we have a million genomes tagged with cognitive measures, a huge swath of politically-incorrect but factually true descriptive statements will be confirmed. We need to work now to avoid confusing the descriptive with the normative and be willing to consider technological fixes for unfair distributions of economically valuable allies, such as embryo selection and direct genetic modification. Our society is so in denial of biological realities, this may not happen in time. But there will be competitive pressure from Asian (and perhaps Islamic) societies that do not share our tabbos.

> willing to consider technological fixes for unfair distributions of economically valuable allies, such as embryo selection and direct genetic modification

A short story about the consequences of normalized post-birth genetic alteration: http://compellingsciencefiction.com/stories/thelittlegods.ht...

A short description of the pre-birth and post-birth conditioning present in Aldous Huxley's famous Brave New World: https://en.wikipedia.org/wiki/Brave_New_World#Fordism_and_so...

The Last Book In The Universe takes a different approach to the issue. A cataclysmic event called The Big Shake destroys society, and only a small group of surviving scientists hidden underground were able to genetically modify their offspring to be superior to the rest of the world. This creates an immensely divisive class system, and the genetically altered humans live and govern separately from the rest of the planet.

This will not be an easy problem to solve, and there is no telling what the future effects will be. But it seems precise genetic alteration is the inevitable holy grail, doesn't it?

I've never actually met someone who was offended by a statement like "on average, men are stronger than women".

If you are saying things like that, and people are getting offended, perhaps record yourself and see what other shit you say and how you say it, and maybe you'll see what they are really offended at.

I'm not walking around saying that because I'm not trying to provoke people, but thanks for the unwarranted judgment.
You just did on here, what does "walking around" have to do with it? And if you want me to take you by your words, take me by mine. I also said "If you say...".

If you don't say those things, and the judgement doesn't apply, then don't get offended.

I'm not offended, even though you're trying to offend me.

Just a suggestion, consider dropping the snarky, aggressive attitude and actually contribute to the discussion I initiated, or move on.

I think I did contribute, but you don't see my point, or you don't think it's important enough to comment on. Consider me "moved on" :)
> record yourself and see what other shit you say and how you say it, and maybe you'll see what they are really offended at

That's not a point, it's an Ad Hominem.

From Wikipedia: A fallacious argumentative strategy whereby an argument is rebutted by attacking the character, motive, or other attribute of the person making the argument, or persons associated with the argument, rather than attacking the substance of the argument itself

And no, I didn't think it was worth commenting on because it's one of my most-encountered fallacies and it just gets tiring.

Why are you fixated on the part we agreed doesn't apply to you? You still miss my point. I'll try one more time. I admit, I don't have a way with words, and I feel I should thank you for your patience, but it seems like you aren't trying to understand me...

Disclaimer, "you" is not YOU, it's whoever says non-offensive things, then complains that people get offended.

You said:

> we have extremists who take offense even at assessments like "Men are on average stronger than women."

If you say something like "on average men are stronger than women" and they get offended, then YOU are the problem. You are a poor communicator. No one says things like that unless they are trying to make a point. What is the point you are trying to make? Are you saying men are therefore better at some activity that strength is involved in? That's obviously not necessarily true.

They are getting offended at the WAY you "teach" them, the bigger point you are trying to make by citing obvious drivel. Perhaps, linking pages to wikipedia, as if they've never heard of "ad hominem" or something. That's why you offend people. Not cuz the facts are right, but because the messenger is a prick.

And again, if this isn't you, don't be an extremist and get offended at stupid shit.

Fixated on what? That sentence was half of your comment.

> If you say something like "on average men are stronger than women" and they get offended, then YOU are the problem. You are a poor communicator. No one says things like that unless they are trying to make a point. What is the point you are trying to make? Are you saying men are therefore better at some activity that strength is involved in?

You're misunderstanding the nature of the sentiment. It's silly and provocative to go around saying "Hey did you know African descendants statistically make better runners?" or "Hey did you know women are weaker than men?", for the same reasons you listed.

But scientists who make statistically valid claims like this are often lambasted, and while some of them (Watson) are trying to use these discoveries to strengthen their biases, many more are not.

And there are useful things to come out of this. For example, the notion that women tend to be more emotional than men. Or, put in another way, that men tend to be more emotionally reserved than women.

We could ignore this fact, or we could call it toxic masculinity, or we could actually take it into consideration when dealing with people we don't know well by making statistical assumptions that guide our behavior. We could have more positive intersexual interactions keeping in mind the statistical strengths and weaknesses of each gender, and not agitating or playing into them.

> They are getting offended at the WAY you "teach" them . . . Perhaps, linking pages to wikipedia, as if they've never heard of "ad hominem" or something . . . That's why you offend people. Not cuz the facts are right, but because the messenger is a prick

I didn't link to Wikipedia, I provided a relevant context. Because people who truly understand Ad Hominem and its dangers are careful not to fall into that trap. But you did, and you are doing so again several times with the above quote. I'm not being a prick at all by pointing out your logical fallacy, even if it makes you feel embarrassed or momentarily ignorant. Being corrected is the price we pay for engaging in these discussions, and the one doing the correcting is not a prick for doing so.

Orthogonal to the matter at hand, I have indeed taken on a certain negative attitude towards you in my arguments because you started off the thread by attacking my character and insulting me, accusing me of doing something I never claimed to do. This conversation started off on the wrong foot and if you had wanted me to be nicer, you should not have begun by dishing out an Ad Hominem.

The entire position of my discussion in this overall thread has been one of rational conservatism, I've even spoken against extremism, so to imply that I am being extremist in such a way that you can back out if you need to and claim that I misunderstood you is only furthering to create animosity in this discussion.

(comment deleted)
How about this: we treat people as individuals regardless of what the scientific facts turn out to be.
If you rephrased that as "we treat people as individuals regardless of the statistics about any classes those people happen to be members of", I'd agree.
How about just, "We treat people as individuals regardless."
Sounds much more like science revealing its still-lingering capacity for producing racist hierarchical judgements of human anatomy
I honestly can't tell if this comment is satire.

If it's not, please point to the racism. The study makes no moral judgement as to whether it's better to have a bigger parietal lobe vs. visual cortex. Do you think the study's results are somehow inaccurate, or improperly obtained?

From the article:

> Only fossils younger than 35,000 years show the same globular shape as present-day humans

and

> They used state-of-art statistics to analyze endocasts of various fossils and present-day humans.

There's nothing uncomfortable about this. They analyzed modern day humans and compared it to humans 35k years ago and found a statistical difference. "Uncomfortable" thoughts fall into the category of pseudoscience which has been long discredited - phrenology, essentially.

Is this any different to the "taxi drivers have bigger [part of] brains" or "musicians have bigger [part of] brains" memes that go around? i.e. true but insignificant
"Only fossils younger than 35,000 years show the same globular shape as present-day humans, suggesting that modern brain organization evolved some time between 100,000 and 35,000 years ago."

If humans reached Australia well before 35,000 years ago and lived in isolation there and the evolutionary pressure in Australia differed noticeably from that in the rest of the world, then that narrows the gap. And, and.

I don't know how much isolation they had. The Sahul Schelf was walkable ground only 18,000 years ago by our current knowledge.
There is the interesting hypothesis that the first people to reach Australia were the Denosovans and African peoples came much later. It would explain a lot of interesting observations about the peopling of Australia, not least evidence of there being people in Australia before African peoples had left the Middle East and why you can only find significant Denosovan genetic ancestory on the Australasian side of the Wallace line.
Your use of "African" seems confusing here. In particular the line "evidence of there being people in Australia before African peoples had left the Middle East" seems to suggest you think Denosovan people didn't originate in Africa.
Well the Denosovans really originated in East Asia somewhere as their ancestors left Africa a long time ago.

We don't really have a good name for the ancient sub-Saharan humans that have contributed most of the genetic background to all living humans.

The problem with the peopling of Australia is the time has been push back so far now (80K BCE) that it is before the ancient sub-Saharans really got much further than the Middle East.

We (sapiens) and perhaps late model erectus are the African species/subspecies of the archaic human group. Denisovans are Asian and neanderthals are European.

It's all based on migration theories which are far from certain, currently. The story gets more complex with every find.

The morrocan find is a spanner, as it "proves" a wide distribution of sapiens early on. This essentially excludes the idea of a migration out of the horn of Africa 200kya, the original out of Africa theory. Modern variations have gotten bigger.

In the Levant neanderthals follow sapiens in the archeological record. The early sapiens are a little more neanderthal looking, especially the brows. This has lead some to a theory that neanderthals evolved from sapiens, and arboreal subspecies.

The Australian story is even more confusing. 70kya is before behavioural modernity. But, seagoing boats are unmistakably modern behaviour. If modernity is strongly genetic, did (almost identical evidence) modernity evolve separately in Oz?...

A lot of mystery still. We have very few finds.

You are making a very large assumption about the evolution of modernity in Australia.
What assumption? The only assumptions I (well, prominent theories) I make are that (a) people got there 45-70kybp and (b) they achieved behavioral modernity (art, tools etc.) around that time or shortly after.
It's Denisovans, after the discovery site in the Denisova cave.
Interesting autocorrect on my iPad, but yes you are right :)
In some cases better known as the autofail. :)

That is a curious change, yes. These things happen, but since people seemed to be following suit I'm glad we cleared that up.

> So one of the groups, either the "in Africa group" or the "out of Africa" group still should have the "old style brains" unless magically the changed happened in both groups at simultaneously.

Just because one group migrated earlier doesn't mean they were genetically isolated. Presumably there were subsequent migrations, counter-migrations (of large populations and smaller groups) and associated interbreeding between them.

That doesn't mean they were completely isolated once they arrived or that evolution stopped once they arrived.
I'd tend to assume that any genetic trait that improves intelligence without significant drawbacks would spread rapidly through interbreeding and selective pressure even without wholesale population transfers. It took about 10,000 years for adult lactose tolerance to spread to its modern range and this brain organization trait would have 35,000 years and potentially give a larger selective benefit.

EDIT: The corollary is that the large genetic component of intelligence is mostly non-linear. E.g. being heterozygous is an advantage and being homozygous a disadvantage.

> I'd tend to assume that any genetic trait that improves intelligence without significant drawbacks would spread rapidly through interbreeding...

I would agree if we were confident that greater intelligence was always worth it, no matter the metabolic cost.

Brains are expensive! Making them bigger incurs additional metabolic costs (and potential complications in the developmental phase). It's very possible that another 20 IQ points wouldn't have really made humans better hunter-gatherers, but would've meant they had to eat more.

Granted, there are likely other ways to get smarter, but it's possible that there would be other systematic tradeoffs required.

Brain size is certainly an issue but from my understanding it's more about the constraints of childbirth than metabolic cost that are restraining it. When you're resting flat on your back your brain uses up 10 of the 100 watts you're dissipating but the variation in brain size given other constraints is pretty low and I'd expect plausible power differences from that to be pretty small too. And brain size only has something like a .3 correlation with IQ so other factors like efficient myelination or organization are probably much more important. I'd expect better myelination to reduce energy consumption if anything. As to organization I'm too unfamiliar with the scaling laws of neurons to be sure but I'd suspect brain organization that increased intelligence at least wouldn't increase energy usage much. So I'm still inclined to view intelligence as being constrained, evolutionarily, by issues of complexity rather than tradeoffs between efficiency and effectiveness as with height.
Note, the original paper is about evolutionary patterns of overall brain shape, which is far from indicating how brain organization evolved. The important parts of brain organization are encoded by patterns of structural and functional connectivity, which are internal to the brain and not well depicted by the overall shape. The paper is great, but the write-up just jumps to some distant conclusions.
I'm reminded of head binding practices at this point.
What is striking is the contrast between how little we understand how the brain actually works, and the bold statements about no difference between men and women brains, everything is nurture/nothing nature, etc. The reality is that we don’t really know. I am dying for science to figure out, but until then I only take claims arguing either way as made up opinions.
> the bold statements about no difference between men and women brains, everything is nurture/nothing nature, etc.

You are attacking a position that is not the common scientist position at all. Your whole comment is a bit surprising given the context. You went out of your way to invent a reason to vent.

"Study finds some significant differences in brains of men and women": http://www.sciencemag.org/news/2017/04/study-finds-some-sign...

https://stanmed.stanford.edu/2017spring/how-mens-and-womens-...

https://www.psychologytoday.com/blog/hope-relationships/2014...

It does not even matter how accurate any of those articles are, this just serves to show that the claim made by OP is wrong. There are plenty of science articles about differences.

So what exactly is the basis for your claim again? Did you do any research of your position at all (and just googling quickly before posting already counts)? It seems to be entirely made up.

> made up opinion

Such as yours? :-)

Talking about making up your own invented antagonistic positions: I am not arguing everyone else pretends there are no difference, I am arguing that some do. Quoting some articles arguing that there are differences doesn't prove anything. As for the ad hominem arguments,...
> I am arguing that some do.

What is the purpose of finding someone, anyone, who holds some fringe opinion to attack it as if its common? You can find any opinion about anything out there after all.

> Quoting some articles arguing that there are differences doesn't prove anything.

It proves that the opinion you attack does not seem to be the opinion of the scientific community. Unfortunately you did not include a single link to show whom or what exactly your comment is about.

I hope you don't consider it rude or an "attack" that I point out that you did not point to anyone/anywhere specifically? Because you really did not. I think your argument would benefit greatly from being more specific.

I have Facebook friends (who I keep because they are ex colleagues and mostly harmless otherwise) whose whole life (judging by their news feed) seems to be centered around finding the most stupid comments on the entire Internet and then posting them to show how stupid they are. Your comment strongly reminds me of that phenomenon. Personally, I consider it not only highly illogical but also a huge waste of time, not to mention what it probably does for your outlook on life to concentrate on the most absurd and ridiculous fringe opinions that you can find.

Also, counter to your latest claim, you make no such distinction at all. You attack the position as if it's common. The Facebook friends I mention at least include specific links that they attack. Not that that would make much sense given that we are here discussing a specific article.

It's interesting to note that a technological civilization has occurred only in the past 200 years. Homo sapiens have been around on the planet for a long time so why is it only happening now?

I suspect that easy access to large amounts of food, more time available for mental activities and the easy spread of information have given us advantages our ancestors did not have despite the apparent similarities in our brains.

One tragedy currently ongoing is that many potentially brilliant minds in LEDCs are suffering from lack of the above three items. It does beg the question - how much mental capability could humanity gain by ensuring everyone on the planet has food, time and access to knowledge.

Increasing the capability raises the noise floor, so you would also need a grooming or discovery mechanism in order for the better ideas to achieve greater adoption.

For instance, if someone comes up with some way for aluminum smelting to use x% less electricity, but no aluminum smelter ever knows about it, no benefit will be realized. Conversely, if all the smelters adopt it, and the inventor is never rewarded, they will simply stop telling people about their ideas, and restrict their thinking to those areas that will benefit them personally.

I would argue that the patents and copyrights system is so lacking in additional capacity with respect to promoting good ideas that the overall benefit to humanity from increasing the raw mental capability will be negligible.

Depends what you consider technology, I would say.

Plant and animal domestication. A heavy hand axe that gave homo erectus a more dangerous clank than a big ram? Fish traps? Hydraulic engineering?

Yuval Noah Harari puts the start around the same time as this article's modern brain, the palaeolithic revolution. The point at which cultural evolution takes over and replaces biological evolution as the driving force of change.

But yeah, we have a ton of wasted potential. Nutrition, education, information and (uncomfortably) inbreeding along with the many types of unavailable opportunities...

Study: The evolution of modern human brain shape

Citation: Simon Neubauer, Jean-Jacques Hublin, Philipp Gunz. Science Advances, 2018; 4 (1): eaao5961.

Link: https://doi.org/10.1126/sciadv.aao5961

DOI: 10.1126/sciadv.aao5961

Abstract: Modern humans have large and globular brains that distinguish them from their extinct Homo relatives. The characteristic globularity develops during a prenatal and early postnatal period of rapid brain growth critical for neural wiring and cognitive development. However, it remains unknown when and how brain globularity evolved and how it relates to evolutionary brain size increase. On the basis of computed tomographic scans and geometric morphometric analyses, we analyzed endocranial casts of Homo sapiens fossils (N = 20) from different time periods. Our data show that, 300,000 years ago, brain size in early H. sapiens already fell within the range of present-day humans. Brain shape, however, evolved gradually within the H. sapiens lineage, reaching present-day human variation between about 100,000 and 35,000 years ago. This process started only after other key features of craniofacial morphology appeared modern and paralleled the emergence of behavioral modernity as seen from the archeological record. Our findings are consistent with important genetic changes affecting early brain development within the H. sapiens lineage since the origin of the species and before the transition to the Later Stone Age and the Upper Paleolithic that mark full behavioral modernity.