People are evolving faster:
Human evolution has accelerated | john hawks weblog
According to the web site listed above, John Hawks, Eric T. Wang, Gregory Cochran, Henry C. Harpending, and Robert K. Moyzis have found that people are evolving more rapidly than in the distant past. That instead of populations staying alike, we are diverging at an accelerating rate. They looked carefully at the DNA of humans and chimpanzees, but you don’t even need to do that to see the evidence of our rapid change. Chimpanzees look a lot like gorillas, who are only slightly less related to us. We look entirely different. They found, what you would not guess, that we were evolving slower earlier.
They put it down to the fact that our culture and our geographic radiation have presented us with new opportunities requiring specific and urgent changes in our constitution. That seems inescapable. Perhaps larger populations produced more mutations, hence more good mutations, as grist for the evolutionary mill, but my own computer simulation of evolution seems to indicate otherwise. A new mutation seems to get fixed as the standard form in a smaller population, and besides, loss of fertilized eggs to bad mutations has its limits. Evolution can only proceed in so many directions at once in a population, since each direction requires selection against the majority that has not yet made the change.
But that is only a quibble. We are evolving faster for whatever reason. I belive it is up to 100 times faster than in the past according to the web site.
The subdivision of populations seems certain, since by and large animals are subdivided anyway. And the challenges of new frontiers that Harpending’s group points to is, I’m sure, part of the cause of the changes they noticed.
But there is another reason for the increased rate of evolution. I may return to the point some time in the future, but right now just think of this. What we have gererally believed in clinical medicine is that the reason it takes 6 months on average for a woman to become pregnant is that it takes that many tries before a viable combination of genes is reached. Thus our complextiy is close to the maximum we can sustain. Any more good genes would mean more bad mutations, more lost fetilized eggs to get those mutations out of the gene pool, and we just can’t afford it, so to speak. Evolution, thus, is put on hold.
But it doesn’t look like it is on hold. It has been going blue blazes. We have changed so much since we were dangling from the same tree as our pre-chimp brethren that many, indeed most, Americans have a serious problem with the idea that we even evolved from a common ancestor.
If you refer to humans as mammals, you will not get much of a reaction. If you refer to humans as chordates, nobody will object even though that includes such modest cousins as the sea quirt and amphioxus. But call a person an ape, and he may take offence. All questions of origin aside, from a purely anatomical standpoint, if you call an orangutang an ape and call a gorrilla an ape, then you must include humans as apes. We are all chordates. We are all mammals. What could be wrong with all being apes?
The reason is a gut reaction. We are just so different from the other apes that many believe in good conscience that we cannot be the same group.
But going back to our theory that humans, and just about every other mammal, are pinned against the wall of carrying all the genetic information we can conserve, how is this consistent with our taking off at an evolutionary gallop?
The answer may in part be our nurturing society. We keep babies alive better. Losing fewer babies to starvation, diarhea, being eaten by turtles or whatever else, we can afford to lose more to bad mutations. That means school’s out. We can lay on new complexity, experiment with new forms, gain valuable skills because we now have the genetic slack. Using those skills to provide ever more secure surroudings, we lose even fewer babies. It all goes faster and faster, we become more complex, more capable but more genetically vulnerable until now we are by far the least fertile animal there is. Other animals also are working against their mutational maximum, but they don’t have our nurseries, our wholesome food, our innoculations.
So it is true, we are so different from other apes that evolution is hard pressed to account for it. Part at least of the accounting is our social order, our nurturing of infants and our erratically increasing technical skills.
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