alt Hacker NewsGenetic drift is not evolution. Every single birth brings about genetic drift. Evolution is gaining or losing specific traits. Individually, humans do gain and lose traits but from an macroscopic view, those traits are just a blip. An cheetah that lose it's ability to run fast many not survive. A human that loses a some useful trait does not die(government assistance. I'm talking about the West because I can't speak for every place in the world) and might even pass that trait down the line. An cheetah that gains the ability to run even faster thrives, outcompete competitors, and most likely pass on this trait. A human that gains a useful trait(faster, stronger, better vision, better hearing) does not amount to much;, might win competitions and make a bunch of money but many people can make a bunch of money without that trait so it's nothing really special. Overall, it's a wash because in one generation, you might have some good genes and the next generation, no so good genes. Therefore, no evolution.
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This is certainly not what I learned to be the definition of evolution in my biology classes.
First, the article is not just proposing genetic drift, which is the change in allele frequency by chance. It is arguing that change in allele frequency is due to natural selection pressure, and that most certainly is evolution. Copied from the Wikipedia entry, because I think it's simple and clear:
> Evolution is the change in the heritable characteristics of biological populations over successive generations. It occurs when evolutionary processes such as genetic drift and natural selection act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations.
That is exactly what the article described.
I believe the traits for humans you should look at are not physical like strength, but social. People with poor social skills are less likely to reproduce in our society. Likewise, culture (and hence memetic evolution) influences birth rates quite a bit and is passed on from parents to children.
Well notably the loss of skin pigmentation evolved in two different ways after migration into Europe and separately into East Asia. There is strong selective pressure in Africa so pigmentation remains there.
And lactase persistence is quite recent. Some people say that Tibetans and some S E Asians are particularly adapted as well to their local environment of high altitude and sea diving but I don’t know anything about that.
>> might win competitions and make a bunch of money
You mean, they might be more likely to have lots of offspring than someone who was disabled and living on government assistance?
Or 500 years ago, be more likely to slaughter the men and rape the women of a neighboring kingdom, than those who stayed home?
Or for a trait closer to my heart, be adept at handling the intellectual requirements of surviving exile and persecution?
You know it's the success they confer toward reproduction that causes traits to survive or not, right? Without reproduction, of course one generation's genetic noise is just noise. And longevity traits don't survive if they hamper reproduction. Just the opposite: Lots of traits that succeed because they improve the chances of breeding are the worst possible things you would want for longevity. Risk taking behavior and all manner of psychoses have survived and thrived for millenia not because the individuals with them live long, but because they breed prolifically.
Genetic drift is essentially random. Alleles at loci more than a few hundred thousand base pairs away are unaffected.
In contrast, an allele under selection pressure drags along large chunks of the chromosome on which it occurs. Statistically, the effect is different. You start to see long-range correlations across the chromosome.
The MHC region, which contains genes that govern many functions of the immune system, has been under continuous selection pressure resulting in extraordinary variability, but also very strong long range correlations spanning the region. It's unlike anywhere else in the human genome. This is a clear signature of evolution.