Do human animals continue to evolve? The evidence is clear that we do, for instance in the case of that small subset of human adults who drink milk, according to this article in Discover Magazine:
Assertion: Because modern humans are a young species, there has not been enough time for major differences to emerge between populations.
This is false. 5 to 10 thousand years ago a set of strangely mutated humans arose. They continued to be able to digest lactose sugar as adults, in contravention of the mammalian norm. In fact, humans are the only mammals where many adults continue to be able to consume milk sugar as adults. The rapidity of this shift has been incredible. 5,000 years ago almost everyone in Scandinavia was lactose intolerant. Today, very few are. The area of the European genome responsible for this shift is strikingly homogeneous, as a giant DNA fragment “swept” through populations in a few dozen generations.
The literature on recent human evolution is still evolving, so to speak. But it is clear that during the Holocene, the last 10,000 years, our species has been subject to a wide array of selective forces. Lactose tolerance, malaria tolerance, differences in color, hair form, and size, seem to be due to recent adaptations. And because of different selection pressures human populations will evolve, change, and diversify. Our African ancestors left 50 to 100 thousand years ago. If 10,000 years was enough time for a great deal of evolution, then the “Out of Africa” event was long enough ago to result in genetic diversification, which we see around us.
It sounds like an interesting hypothesis, but it rests on the assertion that almost everyone in Scandinavia was lactose intolerant 5000 years ago. How did they determine that?
Grumpy: Check out this general article: http://evolution.berkeley.edu/evolibrary/news/070401_lactose
It refers to this study: http://www.nature.com/ng/journal/v39/n1/full/ng1946.html
Here’s the abstract of the other article cited: http://www.pnas.org/content/104/10/3736
addendum: Here is the article you’ll want to start with: http://en.wikipedia.org/wiki/Lactase_persistence
Here’s more on the rapid pace of modern human evolution: http://www.peopleandplace.net/on_the_wire/2011/2/18/jonathan_haidt_morality_binds_and_blinds
With the increase in breeding between people who were born thousands of miles away from each other, something that was very rare for technological and social reasons(racism), I wonder if human evolution will accelerate.