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
Liberal women have small brains. Conservative men have big ones. Whether we use them is an application mystery.
God spoke us into existence - it doesn't get any faster than that.
Unique but not uniform. Some humans--those on the staff of the Guardian, for example--have not yet evolved in this respect.
Me ping
First, I am not an evolutionist. Second, please provide the incontrovertible proof that we are here by a single creator, God.
Do I believe in God? Yes. Do I believe that God created the all forms of life on earth and has a grand plan? Yes. Can I or anyone else provide proof of such? No.
Do I believe as "evolutionists" that there is no God and we are here only by mistake and absolute luck? No.
But I do reject those who proclaiming with certainty that evolution is false.
I'm not sure how commonality implies evolution? It seems reasonable that if you create something and then create a different something you could change or modify your original schematic to change the end result. The products are similar but different and the first did not mutate into the second.
I have always to go back to the question of what evolved first, the heart or the brain? These gigantic systematic changes are just too profound to accept as chance. Further, a dramatic change upward would only occur in 1 individual representative of a species. You would not have an entire generation of a species mutate the same way at the same time without a designer manipulating the change. Therefore, with 1 unit of a species evidencing this 'evolutionary' change, the change would die out in its lifetime. It is unlikely that 1 individual mutation would set the standard for all of the species posterity. Again, this requires far more faith than any creationist scenario. The statistics (science) are staggering.
As a Jew, is my wife going to burn in hell for eternity?
But we know that Chimpanzees and other primates have immensely complex societies relative to other animals. Yet there is no evidence of the type of evolutionary pressure referred to in the article toward human size large brains amongst other primates.
One could argue it is a positive feedback system that makes brain size grow so quickly. The system starts with a complex society and a sufficient brain size. Then, each increment in brain size increases societal complexity which in turn increases brain size and so on. But in that case, why the difference between us and chimpanzees?
Which leads me to one of my principal beefs with evolutionary biology. Almost any fact can be explained in retrospect in the context of evolutionary biology. Here, the authors note the fact that DNA sequences associated with brain development are different from non-brain associated sequences. That is either true or not, replicable or not. But the inference that this difference arises because of evolutionary pressure caused by societal complexity appears, on the evidence in the article, to be nothing more than a WAG with strong post hoc ergo propter hoc overtones. Or in more generous terms, cool speculation.
It may be that the actual journal article provides a better link than the posted article.
I don't dis-believe evolution because I believe it conflicts with my faith, but rather because I find the evidence to be lacking. Want to explain the Cambrian explosion to me?
Can you explain the difference?
You know the earth is only 6000 years old. How do you know?
A leads to B which leads to C; with C possessing repressed but present characteristics of A therefore C has a hereditary link to A ...
When this is seen cross species, what are you proposing happened?
"No man comes to the Father but by Me" is pretty clear. I'm curious about something: What messianic prophecies do Jews consider unfulfilled by Jesus?
MM
There is no Physical evidence to support the Theory.
WAR IS PEACE
FREEDOM IS SLAVERY
IGNORANCE IS STRENGTH
What about "nanotechnology" makes you think it would be useful in the creation of roughly functional and rapidly decaying meat machines?
And why would you accept God's use of "nanotechnology" (whatever the heck you mean by that), but not God's use of evolution?
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.