March 28, 2007

Cochran and Hawks

From World Science:


Human evolution, radically reappraised

Human evolution has been speeding up tremendously, a new study contends—so much, that the latest evolutionary changes seem to largely eclipse earlier ones that accompanied modern man’s “origin.”

The study, alongside other recent research on which it builds, amounts to a sweeping reappraisal of traditional views, which tended to assume that humans have reached an endpoint of evolution.

The findings suggest that not only is our evolution continuing: in a sense our very “origin” can be seen as ongoing, a geneticist not involved in the study said.

Gregory Cochran of the University of Utah in Salt Lake City, Utah, a co-author of the study, said the research may force a radical rethinking of the story of modern human evolution. “It turns it upside-down, pretty much,” he said. But skeptics question some aspects of the work.

The traditional picture of humans as a finished product began to erode in recent years, scientists said, with a crop of studies suggesting our evolution indeed goes on. But the newest investigation goes further. It claims the process has actually accelerated.

It also downplays the importance of a much-scrutinized era around 200,000 years ago, when humans considered “anatomically modern” first appear in the fossil record. In the study, this epoch emerges as just part of a vast arc of accelerating change.

“The origin of modern humans was a minor event compared to more recent evolutionary changes,” wrote the authors of the research, in a presentation slated for Friday in Philadelphia at the annual meeting of the American Association of Physical Anthropologists.

The authors are Cochran and anthropologist John Hawks of the University of Wisconsin-Madison. The findings will also be submitted to one or more scientific journals, Cochran said.

The proposal is “truly fascinating,” wrote University of Chicago geneticist Bruce Lahn in an email. He wasn’t involved in the work, though he did conduct earlier research finding that evolution may still be ongoing in the brain.

Even before the Hawks-Cochran study and its immediate forerunners, Lahn wrote, scientists had already noted a trend of accelerating change in the evolutionary lineage leading to modern humans from ape-like ancestors. But that phenomenon seemed to have occurred over time spans measured in millions of years; it was far from clear that it has continued in the recent past or today, he added.

Hawks and Cochran, by contrast, argue that the trend “is visible even in the last tens of thousands of years,” Lahn wrote. It “runs counter to the feeling in some quarters that the evolution of the human phenotype [form] has slowed down or even stopped in our recent past.”

If the study is correct, it raises new questions about how to define the “origin” of modern humans—a rather arbitrary decision in any case, Lahn remarked.

The origin is “defined probably more as a matter of convenience rather than reflecting any actual watershed evolutionary event,” he wrote. That is, it’s “useful to say that any past creatures that are within certain levels of similarities to us today should be considered as ‘the same’ as us.”

But if the changes that accompanied this event are only a trifling part of a wider trend, he added, it becomes reasonable to ask whether that further deflates the rationale for calling it an origin.

“In a sense,” he wrote, one could say “the origin is still ongoing.”

Evolution occurs when an individual acquires a beneficial genetic mutation, and it spreads throughout the population because those with it thrive and reproduce more. Ceaseless repetitions of this can change species, or produce new ones. As beneficial genes spread, harmful ones are weeded out; the whole process, called natural selection, propels evolution.

Hawks and Cochran analyzed measurements of skulls from Europe, Jordan, Nubia, South Africa, and China in the past 10,000 years, a period known as the Holocene era. They also studied European and West Asian skulls from the end of the Pleistocene era, which lasted from two million years ago until the Holocene.

“A constellation of features” changed across the board, Hawks and Cochran wrote in their presentation. “Holocene changes were similar in pattern and... faster than those at the archaic-modern transition,” the time when so-called modern humans appeared. But these changes “themselves were rapid compared to earlier hominid evolution.” Hominids are a family of primates that includes humans and their extinct, more ape-like though upright-walking ancestors and relatives.

Hawks and Cochran also analyzed past genetic studies to estimate the rate of production of genes that undergo positive selection—that is, genes that spread because they are beneficial. “The rate of generation of positively selected genes has increased as much as a hundredfold during the past 40,000 years,” they wrote.

There are ways to detect positive selection in genome data. But Mark Thomas, a genetic anthropologist at University College London, was skeptical that these would be enough to make Hawks’ and Cochran’s case. “The issue is that the most powerful methods for detecting selection are ones that lose their sensitivity going more than 30,000 years back,” he said. Other techniques can’t “distinguish between selection and population growth.”

Thomas added that he understands the skeletal data to show something different from what Hawks and Cochran say, but that he would need a fuller account of their findings to make a judgment.

Hawks and Cochran said some of the most notable physical changes in humans have been ones affecting the size of the brain case.

A “thing that should probably worry people is that brains have been getting smaller for 20,000 to 30,000 years,” said Cochran. But brain size and intelligence aren’t tightly linked, he added. Also, growth in more advanced brain areas might have made up for the shrinkage, Cochran said; he speculated that an almost breakneck evolution of higher foreheads in some peoples may reflect this. A study in the Jan. 14 British Dental Journal found such a trend visible in England in just the past millennium, he noted, a mere eyeblink in evolutionary time.
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My published articles are archived at iSteve.com -- Steve Sailer

20 comments:

Fred said...

After reading that title I almost expected the story to be about Cochran coming up with an evolutionary explanation for hawks like [insert name of Jewish Bush foreign policy official here (if there are any left)].

Interesting though that brains have been getting smaller. Does that mean that blacks with smaller brains are more advanced than whites with larger brains?

ben tillman said...

Computers have also been getting smaller.

Monroe said...

It doesn't make clear what part of the brain is shrinking. I expect is whatever helps survival in a tough "wild" environment, rather than a easy domesticated one.

Looking at Australian Aboriginals for a clue provides contradictory signals. The Australian Aboriginals have smaller brains, but a larger visual cortex, than Caucasians (AAs are known to be better trackers etc) - but this also causes a large forehead.

Today's civilisation tends to concentrate daily activity on very minor mental activity, followed by witless (over) consumption. Rather like a human battery chicken farm. I'd love to see data on very recent (last 100 years) changes in brain morphology.

RBC said...

Brains getting smaller is an essentially inevitable side effect of domestication. Wolves are smarter than dogs, for example. In some sense, dog breeds with different hunting specialties (pointing, retrieving, etc.) are mentally equivalent to wolf puppies stuck at a certain stage of development. The same thing happened more recently: when Dmitri Belyaev tried to breed tame foxes for fur farming, they started acting like dogs. The best overall explanation is that in domesticated species, the brain simply does not develop for as long, so it ends up smaller -- just as the primary difference between human and chimpanzee brains is that ours develop for longer. For a good introduction to this kind of research, check out the first chapter of Nature via Nurture by Matt Ridley.

This is consistent with other genetic research posted here in 2005 showing that humans have genetically domesticated ourselves over the last 50,000 years just as much (or more) than we have dogs, cows or wheat. In fact, one author of the current paper is quoted in that column as calling it central to his own research, for which we'd "just have to wait". Apparently the waiting is over.

As for the black-white difference, start with the brain size over time graph in J. Phillipe Rushton's Race, Evolution and Behavior which shows where different races split off the main curve of hominid brain growth. Then have all three human subgroups shown curve downward again at the right edge of the graph (the recent past). Whites' brains kept getting bigger for longer than blacks' brains did, and now both are getting smaller again. The racial difference seems to be a different effect from the one discussed in this paper.

Monroe said...

rbc is broadly correct, except dogs did not evolve from wolves, but from more probably from wild dogs ... contrary to popular opinion. see http://darrennaish.blogspot.com/2006/10/controversial-origins-of-domestic-dog.html

tommy said...

Hawks and Cochran, by contrast, argue that the trend “is visible even in the last tens of thousands of years,” Lahn wrote. It “runs counter to the feeling in some quarters that the evolution of the human phenotype [form] has slowed down or even stopped in our recent past.”

Honestly, I don't see how this is tremendously surprising. We haven't been out of Africa for more than 150,000 years. The differentiation of human races has obviously occurred with incredible rapidity since that time. Civilization wasn't a factor for any group of human beings until less than 10,000 years ago. For some remote groups of people in the Amazon or Papua New Guinea it still isn't.


A “thing that should probably worry people is that brains have been getting smaller for 20,000 to 30,000 years,” said Cochran. But brain size and intelligence aren’t tightly linked, he added.

I'm curious as to whether anyone can provide more details about this. How have they determined this? I believe Neanderthals are thought to have had slightly larger brains than modern humans.

joshrandall said...

Evolution occuring even more rapidly than previously thought? Fascinating! I wonder how our daily lives influence the process of evolution? Well,lets see;last night I watched American Idol and Dancing WithThe Stars. You dont...supose...there kood be sum...re, uhmm,re,regreshin..okurran on a daly...uhhhh...basis...basis loaded...wut wuz I sayin? O no i hungri got banana? Ug! Oooga booga!

corvinus said...

Lemme 'lone, I'm 'batin'. I sure want some Brawndo. It's got electrolytes. Cr@p, I'm out of money. I like money.

Anonymous said...

A larger brain might allow for more processing of various sensory signals to evaluate danger, opportunity, etc. wrt animals, other potentially dangerous humans, etc.

While a smaller more specialized brain might allow for deeper focus on tasks. What makes humans unique is the acceleration in our tool-making. If you look at tools over the last 10,000 years, you go from stone tools to bronze to iron/steel tools.

And the societies that can successfully organize around better tools, particularly for warfare, tend to be more successful.

The Egyptians, Hittites, Persians etc organized around the chariot and bow tools. But were beaten by the Greeks organized around the heavily armored and shielded spearmen/pikemen. Who were beaten by the Romans organized around lines rather than squares of the same thing with short stabbing swords. Who were beaten by nomadic horsemen. Who morphed into armored knights with heavy Roman-style pikemen infantry. And so on.

All of THAT requires an evolutionary change in perception of a broad range of threats to ever more extreme specialization with emphasis on co-operation. A stone-age tribe in deep New Guinea might require huge generalization from each member; while today's modern societies require extreme abstract thought (such as this article and the discussion).

Cochran and Hawks work might (yes I'm the Dark Ages commenter) indicate how Europe was able to move rapidly from a situation where literacy was almost unknown, life was extremely rural and tribal and optimized for physical survival rather than intellectual activities and specialization, to well intellectual activities and specialization.

If I had to guess I'd venture that dynastic struggles, lots of migratory pressure (all those tribes fighting over the corpse of the Roman Empire), and various Muslim and Viking raids led to warfare being the "starter seed" for a climb upward to specialization.

[European brains circa say 50,000 BC to perhaps say 1100 AD may have been optimized for sensory perception and processing, i.e. will a freeze be coming, is that man approaching friend or foe, is the food spoiled or safe to eat, where is that spear thrust coming from? And African brains may be coming to that transition to specialization later.]

IQ seems to measure abstract reasoning (a specialization) and racial differences in IQ might be driven by more or less specialization driven natural selection. I.E. the degree to which tool making is genetically rewarded. Cochran and Hawks suggest that this genetic rewarding for tool making / specialization might be far more rapid than we think.

[One thing that stands out in thinking about Dark Ages Europe and Africa is the difference in ship building and armies. Starting from Athens and other Greek City states to the Romans and Vikings and various other European tribes, the greatest military (and hence evolutionary advantage) came from combined naval and land force power. Requiring lots of co-operation and specialization. African's lack of need to venture to the sea, compared to the relative paucity of the Med's poor farming soil and need for the sea for fishing/trading may explain the difference in the civilizational rise.]

blueman said...

The Egyptians, Hittites, Persians etc organized around the chariot and bow tools. But were beaten by the Greeks organized around the heavily armored and shielded spearmen/pikemen. Who were beaten by the Romans organized around lines rather than squares of the same thing with short stabbing swords. Who were beaten by nomadic horsemen. Who morphed into armored knights with heavy Roman-style pikemen infantry. And so on.

..and the worlds biggest power was sent into a tailspin by a few boxcutter knives.

According to military old-hands, one of the biggest missteps by the US in the operations in Iraq and Afganistan, was the lack of "human intelligence". I'm not kidding - they use those words. What that means is that, for instance, there is only six native Arabic speakers amongst the whole US army in Iraq.

Time and time and time again through history, the dominant power becomes mentally lazy, relying on it's superior technology. The archetypical example is Rome. This cycle seems inevitable.

Anonymous said...

What, nothing about Obama's forehead?

James said...

Their findings are based on fossil bones? Specifically fossil skulls? How much can they really say just based on that? Humans are more than brain.

Steve Sailer said...

Tool-making goes back millions of years, but it was crude, mostly involving whacking rocks together. Then about 50,000 years ago, you see a great leap forward in material culture. By the time of the Iceman in the Alps 4 or 5 thousand years ago, even illiterate tribesmen carry an impressive variety of tools that a modern backpacker wouldn't sneer at.

I've vaguely theorized that the growth of tool-making capacity is related to nerdism in modern humans, while leaders of war and large scale hunting parties were the equivalent of the modern big men in politics and business.

Anonymous said...

Uh oh, some former NBA player said jewish people were crafty and shrewd:

http://sports.espn.go.com/nba/news/story?id=2816356

Everyone knows there are no group differences. I've never noticed any differences between black people and jewish people for instance.

Anonymous said...

Human evolution:

Somebody on another post commented on AIDS and what its effect on Africans might be and he brought up intelligence. I have always wondered about that and have gotten so bored with people who speculated about "genetic mutation that would keep one from succumbing...". To me, it seems greater intelligence will be the ultimate weapon and will spread far faster than waiting for the holy grail mutation. It is a lifestyle disease and life is an I.Q. test.
I believe Christianity, or more accurately, Judeo-Christian values are important vis a vis intelligence. Monogamy, prohibition of pork (especially in ancient times when it may have been more dangerous to eat), circumcision, no sex with other men or animals, etc. all have one thing in common: they cut down on germ transmission.

In our time, it has been fascinating to learn about how much germs affect us and have become implicated in ailments once thought understood (15 years ago, nobody used hand sanitizer, now it's ubiquitous). I think we're only at the tip of the iceberg.
Further, while we are able to appreciate the worst results of some of the STDs: death, infertility pre-term labor, surely the ability to produce the best child possible would be hindered in more invisible ways that we haven't yet discovered.

Emily

Anonymous said...

"I've vaguely theorized that the growth of tool-making capacity is related to nerdism in modern humans, while leaders of war and large scale hunting parties were the equivalent of the modern big men in politics and business."

Exactly Mr. Sailer and that's my point again. [The Dark Ages obsession guy again]

WHAT if both requirements (tool-making and military leadership) were encapsulated in one person? That the leader must be both "nerd" perhaps not a tool-maker in the garage tinkerer sense but one who uses complex and abstracted military systems, as one gigantic "tool" and also "leadership" defined as getting people to do things they don't like to do (run a good risk of nasty death)?

Could that be the Dark Ages inflection point? The requirement to understand boat-building and naval power (with all those Vikings sailing in unexpectedly) and how to use an Army as a "tool" along with a Navy?

Blueman -- given trends isn't relying on superior tech the better bet? The Romans didn't adapt to the changing times (not enough real Romans of certain loyalty fighting) and got beat. Given that today's tech will obsolete soon isn't that a huge competitive advantage?

What's interesting is how many guys who fought in Iraq are coming into the Defense industry with lots of interesting new solutions for IEDs, snipers, mines, etc.

blueman said...

given trends isn't relying on superior tech the better bet?
Well, the problem is relying. It's human psychology to reach for the footstool and relax once a certain level of technology and advantage has been reached. But the next door neighbors won't be relaxing. The Japanese reached their pinnacle, and now they're taking a nap while South Korea and China are poised to overtake. That's the cycle. In the US, helped by labor-saving devices (and increasingly thought-saving devices) the population is unbelievably fat, dull, ignorant and lazy. You can't expect the US to hold on to it's position when it's a nation of mouth-breathers who elect a president in their own image.

MarcZ said...

Somebody on another post commented on AIDS and what its effect on Africans might be and he brought up intelligence. I have always wondered about that and have gotten so bored with people who speculated about "genetic mutation that would keep one from succumbing...". To me, it seems greater intelligence will be the ultimate weapon and will spread far faster than waiting for the holy grail mutation. It is a lifestyle disease and life is an I.Q. test.

The impact of HIV/AIDS on African intelligence will be zero to none. The best defense against contracting HIV/AIDS in Africa is simply to live in a society that practicies male circumcision. This is a cultural norm that has nothing to do with intelligence.

True, in countries like Swaziland and South Africa with roaring epidemics, there might be some selection going on. But the majority of sub-Saharan Africans do not live in countries that have or will probably ever have such high prevalance rates.

Anonymous said...

Male circumsion does not protect against AIDS.

I really dont know what differences in brain size and morphology between "blacks" and "whites" has to do with natural selection either, since the degree of gene flow between different human population in the past 200,000yrs since our speciation has been such that greater differences exist between the genotypes of two white americans born in the same district of Salt Lake, than between the genotypes of one of those americans and an Australian aborigine born in the Northern Territory.

The self-domestication research is great, check out niche construction research as well (Odling-Smee, Laland, etc - www.nicheconstruction.com), which would suggest our domesticated status to be some sort of social niche, a manipulation of our social environment which ahs in turn affected our genotype, hand in hand with our construction of our physical environment. Domestication doesnt necessarily lead to stupidity, but it does cause different selection pressures to act on different areas of the brain - like, for example, tolerance and sensitivity to others' actions and intentions (shown to emerge in foxes after only 50yrs of intentional selection for tameness). It also causes body size to decrease generally, and to become less robust, which has clearly happened in humans (though probably more due to food processing diminishing the need for large jaw muscles).

If you need a reference for those look at Richard Wrangham's work - he's done various experiments on the effects of domestication on cognitive traits, and has hypothesised cooking to be responsible for some of our unique evolutionary characteristics, which is also an approach that would be interesting to use in terms of recent changes in brain morphology, since clearly our diet as well as our lifestyle has changed considerably in the last few centuries...early agriculturalists certainly shrank in stature in response to a lack of nutrients and spread of disease, due both to urban living and a reliance on type 3 staple foods...

Charlotte

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