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
Please refer to my previous reply.
As long as we know how to use them. I worry the next generation has turned off half it's processing power.
Macro my friend, Macro... the fundamentalists seem to have this foolish idea that the theory of evolution, is some how at odds with the divine. Its not.
It's a theory, and yes, even MACRO evolution is NOT in conflict with faith, and that's according to Vatican edicts on the matter.
Again, Evolution (in all things) is observable evidence that God exists. Saint Thomas Aquinas addresses this issue long before Darwin ever existed or proposed his theory of evolution.
Should macro evolution be proven beyond a reasonable doubt tommorrow it no more negates God than the fact evil in the world exist would negate God nor creation. Intelligent Design and Evolution are NOT in conflict and only the most aethist scientist or radical fundamentalists believe they are.
I was just joshin.....
Me too!
Tell that to the "antiwar" "people"... he he he
It would seem that "acts of God" would indeed motivate evolution toward smarter people.
Yes, and it is random, directionless, purposeless evolution that worked so hard on creating the human brain. It does seem that evolutionists exempt themselves from consistency when convenient, doesn't it?
Yes. By definition.
You are overlooking two crucial aspects of the science, here. First, natural selection. Second, inheritability.
The first answers the "chance" fallacy; the second answers the question regarding the "one out of a population" issue.
Genetic changes or mutations occur for many reasons. Of those mutation, differential reproductive success means that only the favorable changes will be passed on to the next generation. If the mutation is bad, the organism will not reproduce or be less successful at reproduction than average. If it is favorable, the organism will reproduce at a greater than average rate. Remember that at its heart, evolution is descent with modification.
What does this all mean? If, as the result of the mutation, an organism is more successful at producing offspring, the more of the next generation will have that mutation as part of its genetic code. Those organisms will, also, leave more of their offspring in the succeeding generations that those without that mutation. Thus, the mutation does not remain within "1 unit of a species". After a number of generations what started with one individual propagated throughput the population.
There is an element of chance in there, but remember mutations are not necessarily objectively good or bad. They merely effect the relative reproductive success of the organism. (I.e., a mutation which decreased the amount of body hair might be favorable in an aquatic environment, but disfavorable in an alpine or arctic climate.)
But one possible valid answer; one that does NOT, however, address the issue at hand: why and wherefore does a huge amount of genetic material get carried forward - were it not for some underlying commonality?
On the practical level, we already know as humans we can evolve both plants and animals into more desireable forms by selectively breeding; so we already have before our very eyes proof of 'evolution' on a minor scale, therefore, we know it's possible ...
Do you know anywhere it is written or indicated that all plants/animals were created/based on one another - from all indications biblical animals could have equally been comprised of purely 'dog', 'cow' or 'horse' stuff as the elements we know they are comprised of ...
If you don't agree with the evidence, that's fine, its those that dismiss evolution as though its somehow an affront to God.
Cambrian explosion:
"A span of 40 million years embraces the appearance of the first small, simple shells that may have been secreted by metazoans and the subsequent exuberant diversity of Chengjiang and the Burgess Shale. This is not so short a time for an evolutionary ‘explosion.’ However, the proliferation of animals with well-differentiated hard parts characteristic of specific metazoan phyla was largely restricted to the last 15 million years of this interval" (Thomas et al. 2000, p. 1239).
Evidence of life pre-cambrian is being exposed more and more daily. The life forms were soft bodied, so they did not leave the fossil traces that the Cambrian hard bodied animals would later leave.
55 Million years is a long time particularly when you figure the first 40 Million remained largely simple shelled type of organisms. Once however this "trait" evolved into larger animals it is not suprising that those animals would suddenly gain dominance and diversity. As a hard bodied animal certainly has a benefit over a soft bodied one.
The first hard bodied predator (or prey) for that matter, would rapidly push the evolution of predator and prey toward more genetic preference, as these would be more likely to live. If hard bodied prey dominate the environment of soft bodied animals, they would quickly decimate the environment and likely leave lots of new niches for new animals to fill.
Now, of course this is purely conjecture, since none are now living that saw that time, but 55 Million years is a LONG time, hell even 15 Million years is a long time for an "explosion".. considering that human beings date back only a few hundred thousand years.
Heheh.. that is funny isn't it?
Ice Age.
These are not articles nor discussions about conservatism or advancing the cause of conservatism.
Shouldn't these be posted under General/Chat or Bloggers/Personal?
What defines these as "Activism" for conservative causes?
Thanks in advance.
So does the word of God say that I shall not kill (KJV) or does it say I shall not murder (NIV)? Both are purported to be the Word of God, but both have very different impacts on acceptable behavior.
In this case NIV is the more correct translation. One should always read the subject matter for content consistency. Common sense allows that one may use lethal force if needed in self-defence. Society may condemn a vicious incorrigible murderer to death but this is not murder.
They probably went extinct pretty quick. There just weren't enough purple people around for them to eat.
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