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
Compare the tendency to produce the higher levels of genius, today, in any population group, with Sir Francis Galton's example of the population of Attica about 2400 years ago, where 90,000 produced a dozen men who throughout all history since, have remained at or near the top in their respective disciplines. Or contrast even the top 25% of the voting population of America today, with those who were persuaded to ratify the Constitution, by reading the scholarly disertations in the Federalist Papers, to witness the dumbing down of our own population.
William Flax Return Of The Gods Web Site
Freeper Alter Kaker supplied some information in post 51 concerning common lineage of bears and dogs.
How is this insufficient to support species transition? Is there something key missing?
in fact it was almost .. instantaneous ...
The truth or falsity, reasonableness or unreasonableness, of a belief must stand independently of those who accept or reject the belief.
If a controversial claim could be established as true because it is supported by experts, then contradictory beliefs would be true, which is absurd.
Do you know what a genetic fallacy is? One can't legitimately judge a proposition or belief by the person who is stating it, rather, one must judge it through the arguments for and against it. Please don't expect those capable of critical thought to take you seriously if you use ad hominem in place of valid argumentation.
>And how do you reconcile Biblical admonitions against dishonesty with the deliberate dissemination of falsehoods to unsuspecting students?<
Nothing to reconcile.
It is evolution which is false.
I only assert creation.
more later.
You are all off base. Everyone knows that Odin created the first man Aske from an Ash tree, and Embla (first woman) from an Elm tree and endowed them with life and souls.
I get very upset that the local schools teach this junk science of evololution instead of the truth. How do I know this, it's written in the Eddas for all to see plain as day.
Are we to believe we are descended from monkeys? The Ash tree is our true ancestor.
As some have been doing......
I'm guessing that you are trying to make a point....
Is there something you fear about reading The Bible?
Arthur C. Clarke and Stanley Kubrick knew about this 40 years ago.
I think (personally, based on my own anthropology reading) that it was the *kind* of society which formed that made the difference. In chimp and gorilla groups, there's no nuclear family. Males may "own" a group but there's no real individual loyalty to one female & her offspring.
At some point proto-hominids transitioned to people (probably 150,000 or so years ago.) It may have been something so simple as pair-bonding between male and female, with the male being *responsible* for the female and her offspring.
One thing you can say for sure about *modern* primitive hunters is that the men don't hunt in a "vacuum." Even though the women don't hunt, they have huge jobs to fulfill - like taking care of the camps, processing the kill, preserving the meat, doing all the sewing and preparing of hides, as well as a good portion of the artwork (decorating hides.) So development of the brain occurred in *both* sexes, without the gross sexual differences in size and behavior seen in the great apes.
This situation is optimal for language development. Males "needed" language to work cooperatively with other men; to persuade a woman to set up a partnership (marriage) with him. Females "needed" language to pass their arts on to other females; to bond with their mates and probably most important - as a means of better raising infants. At some point the survival value of being *talked to* and *communicated with* as an infant had to be phenomenal.
Is there something you fear about answering my question?
That's silly. Please tell me Homer Simpson thought that up! Please God!
Dogs with wings? Yep, there are those and more.
This works both ways. It should be obvious that one cannot use science knowledge to infer religious truths anymore than one can use religious knowledge to deduce scientific truths.
It is those, such as R. Dawkins, who perform reductionism (materialism scientism) while claiming they're not reductionists because there's nothing to reduce. This is an affront to anyone persuing knowledge transcending the narrow sphere of science.
Evolution has had a greater impact OUTSIDE biology. This should tell us that it is being used far outside it's limited - and rightly questioned - area of knowledge.
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