A friend put me onto this human genetic research program (no, no, it all sounds reasonable, keep your shirt on; no one is looking for the missing link andyou are him and the genetic police are waiting outside … wake UP, will you?):
Ethnically diverse people are donating DNA to science, and the wealth of genomic data emerging from the project already is shedding light on human evolution.A decade ago it was a big deal to spell out the entire DNA sequence of a single human being. That event marked the success of the initial Human Genome Project. Now hundreds of human genomes have been decoded. Scientists who study human evolution are using the new data to make discoveries about how Homo Sapiens may have adapted to an ever-changing, ever-challenging environment.
But a puzzling claim immediately follows:
New traits become established in human populations because they confer a survival and reproductive advantage. In Darwinian terms they are “positively selected.” Individuals who lacked the genetic variant responsible for an important trait often did not survive long enough to leave progeny.Mutations in general may be harmful or of no consequence, but some mutations make for a better-adapted organism. Over time these new and advantageous genetic variants can usurp those that dominated previously.
Yes, but one problem that set me thinking was loss of adaptive traits. I tried explaining it to a friend in this way:
Let us say that, as an evolutionary legacy, a woman is immune to leprosy. She has always lived in a northern climate where she was unlikely to be exposed to the disease. If her daughters marry immigrant men who do not have that immunity and the trait is lost over time, it would still be of no consequence provided they all stayed in that climate.In the end, no one would get leprosy, maybe no one would know about the existence of the trait, and the trait, which doesn’t matter where they live anyway, would just get lost.
So, I asked, don’t beneficial evolved traits get lost all the time? Is this correct?
The friend wrote back to say,
Yes, they do get lost all of the time, and they are more likely to be lost when there is no consequence to the loss.
Hmmm. Still more trouble for Darwinism: The rare beneficial trait that results from natural selection has no special protection from just getting lost.