What is the Significance of This?

I don't know what to make of this story. Something's gone wrong somewhere in the reporting.

The sophistication of the human brain is not simply the result of steady evolution, according to new research. Instead, humans are truly privileged animals with brains that have developed in a type of extraordinarily fast evolution that is unique to the species.

"Simply put, evolution has been working very hard to produce us humans," said Bruce Lahn, an assistant professor of human genetics at the University of Chicago and an investigator at the Howard Hughes Medical Institute.

"Our study offers the first genetic evidence that humans occupy a unique position in the tree of life."

Professor Lahn's research, published this week in the journal Cell, suggests that humans evolved their cognitive abilities not owing to a few sporadic and accidental genetic mutations - as is the usual way with traits in living things - but rather from an enormous number of mutations in a short period of time, acquired though an intense selection process favouring complex cognitive abilities.

One has to ask, is this really news? After all, we know for a fact that stone tool-making didn't get off the ground until 2.5 million years ago at most, and that there's no evidence of mastery of fire before the last 400,000 years. It's obvious that intense selection would have had to occur in order for our kind of intelligence to appear within such a short timespan, isn't it?

Prof Lahn's team examined the DNA of 214 genes involved in brain development in humans, macaques, rats and mice.

By comparing mutations that had no effect on the function of the genes with those mutations that did, they came up with a measure of the pressure of natural selection on those genes.

Hmm, I'm not so sure of the wisdom of using fast-evolving species likes rats and mice as outgroups. I'll have to read the actual paper before I pass judgment, however.

The scientists found that the human brain's genes had gone through an intense amount of evolution in a short amount of time - a process that far outstripped the evolution of the genes of other animals.

"We've proven that there is a big distinction," Prof Lahn said. "Human evolution is, in fact, a privileged process because it involves a large number of mutations in a large number of genes.

"To accomplish so much in so little evolutionary time - a few tens of millions of years - requires a selective process that is perhaps categorically different from the typical processes of acquiring new biological traits."

Is it really fair to say that human evolution is "privileged" when of the time-scale one is talking about - tens of millions of years - for only a small fraction (6mya) have humans actually been evolving separately from chimps and gorillas?

As for how all of this happened, the professor suggests that the development of human society may be the reason.

In an increasingly social environment, greater cognitive abilities probably became more of an advantage.

"As humans become more social, differences in intelligence will translate into much greater differences in fitness, because you can manipulate your social structure to your advantage," he said.

"Even devoid of the social context, as humans become more intelligent, it might create a situation where being a little smarter matters a lot.

This would certainly support what I already believe, but how exactly does it follow from this research? I don't see that it does, though in this case I suspect that the fault lies more with a reporter pushing for a definitive explanation where there is none than with the scientist responding.

This looks a lot to me like a big fuss over very little, scientifically speaking, and looking at the abstract of the relevant article doesn't do anything to contradict said suspicion. As far as new insights go, the most I expect from this research is that it will someday help to pin down when exactly traits like language became part of the human repertoire.

 

Comments

[eoin]

Whats new is,I think, that he claims to have found proof of the large number of genes that mutated during human ( and primate) evolution with regards to intelligence. The rest is just the Just So story about humans being social, and human socialization leading to higher intelligence etc. I believe that too ,but it is not really proven by the discovery of "intense genetic pressure" on the genes for human intelligence.

[praktike]

I would think that the development of language would be a key element of sped-up evolution.

In any case, we already know that evolution doesn't have to be "slow." Fish tend to evolve like gangbusters.

[razib]

i might have to come back to blogging to post on this...but will wait until the i read the CELL paper, but, my reaction was the same because paleoanthropologists have always noted that primates have large brains, that homonids have larger brains, and that cranial capacity increased steadily up until 200,000 years ago with an increase in rate between 600,000-200,000 years ago.

the conundrum of course is that though anatomically modern humans existed 200,000 years ago (in africa) there isn't a great deal of evidence of culture as we know it. the traditional model holds that the great-leap-forward happened around 50,000 years ago, though new findings are pushing that back, nevertheless, i haven't seen anything bridge the gap to 200,000 years B.P.

many palaeoanthpropolists and cognitive scientists infer that there must have been a point mutation which resulted in a saltational leap in cognition at some point. the new evidence from dogs in terms of tandem repeats influencing gross morphological variation might point to something along those lines.

anyway, it might be that the fossil hunters just haven't looked hard enough for culture, that to me is the only other alternative. i don't believe that symbolic expressions of culture was an "invention" like writing or the wheel, the evidence from tasmanians to me suggests that no matter how much a small isolated group degrades in their material culture, they still retain the suite of behavorial tendencies that produces art, which you can't find in the earliest humans with modern cranial capacities....

[Abiola Lapite]

"the traditional model holds that the great-leap-forward happened around 50,000 years ago, though new findings are pushing that back, nevertheless, i haven't seen anything bridge the gap to 200,000 years B.P."

I doubt there ever will be. It seems to me that a lot of people make the mistake of thinking that a change in the way brains work must be reflected in the bodies of those who have them. My own guess is that fully modern cognition is at most 80,000 years old: the anatomically modern humans found at Qafzeh and dated to 96,000 years ago showed no sign of thinking any differently from their Neandertal neighbors.

"the evidence from tasmanians to me suggests that no matter how much a small isolated group degrades in their material culture, they still retain the suite of behavorial tendencies that produces art, which you can't find in the earliest humans with modern cranial capacities...."

Indeed. It's almost as if modern humans can't help doodling or leaving some sort of glorified graffiti wherever they go, and even if populations were small in the upper paleolithic, one would at least expect one or two pieces of evidence that modern thought patterns existed, given a timespan of 100,000 years.

[dsquared]

I suspect that if you compared penis sizes relative to body mass between male great apes and human beings you might get similar results, although it would be a bit more difficult to get your diagrams published in the popular press. Not sure with what conclusions, but it wasn't just in the cranium that things were going on ...