Posted on 12/29/2004 9:14:28 AM PST by aculeus
Emergence of society may have spurred growth
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.
Evolutionary biologists generally argue that humans have evolved in much the same way as all other life on Earth. Mutations in genes from one generation to the next sometimes give rise to new adaptations to a creature's environment.
Those best adapted to their environment are more likely to survive and pass on their genes to the next generation.
The evolution of a large brain in humans, then, can be seen as similar to the process that leads to longer tusks or bigger antlers. In general terms, and after scaling for body size, brains get bigger and more complex as animals get bigger.
But with humans, the relative size of the brain does not fit the trend - our brains are disproportionately big, much bigger even than the brains of other non-human primates, including our closest relatives, chimpanzees.
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.
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."
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.
"The making of the large human brain is not just the neurological equivalent of making a large antler. Rather, it required a level of selection that's unprecedented."
Guardian Unlimited © Guardian Newspapers Limited 2004
Don't forget the genius, Jacob Bronowski!
Then you aren't having enough of a night!
Yes, he certainly did! He's been replaying lately on the History Channel or one of the Discovery channels. Or somewhere.
Merlot? Ugh! It's a rare Merlot that is worth drinking.
OTOH, we've been cleaning out the cellar by drinkling all the "Pinot Grigio". After a few glasses you do get used to it. But I think tomorrow is going to be a baaaaad day.
Just like tracing DNA relationships by the viral infection scars, you can trace the "scientific" basis of creationist scholarship from the bloopers in the stuff they crib off each other. I'll have to look for that pairing of "The Descent of Man" and "Preservation of Favored Races" in future posts.
My other favorite is "... the boy from Tukana ...," where "... the boy from Turkana ..." occurs in the Lubenow original. (Turkana being a lake in Africa and Lubenow being a creationist.)
There seems to be an odd disorder in your taste buds. Well, more for me!
It's a curious error. First we have this:
THE ORIGIN OF SPECIES BY MEANS OF NATURAL SELECTION, OR THE PRESERVATION OF FAVOURED RACES IN THE STRUGGLE FOR LIFE. .
And then there's this: THE DESCENT OF MAN, AND SELECTION IN RELATION TO SEX.
The next two have it wrong also. The last two, however, seem to have that subtitle appended to Origin of Species, so they're apparently okay.
Sure, I just want to repeat it, as there are folks on this thread who did not participate last time.
It's the time-frame, right, that you don't agrre with; for surely you believe that it DOES speak to people today, don't you?
You say to-mah-to.........
Are you talking about DNA replication here?
They are true believers and have no disagreements. The reason for this is that they know the theory is true. When believers know that strongly that something is true they don't question it. (Notice how absolutely no proponent of evolution here, ever questions even one little thing about it.)
And "when you don't question it, you're living by faith, not by science."(Ian Stewart, quoted from Does God Play Dice? The Mathematics of Chaos)
For these people here, few of them scientists, mind you, they are defending dogma
And if you outlive me, you win.
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