It’s easy to wonder to what degree humans are still subject to natural selection; from the perspective of someone living in an industrialized western nation, it can look like everyone gets to live long enough to reproduce and can successfully raise their offspring to adulthood. Of course, in some parts of the world, that’s much less certain than in others, and furthermore, evolution is complicated. A new study, using data from the Framingham Heart Study, has found that natural selection does still seem to be at work on us.
Researchers used data from the 60-year Framingham study on more than 2,000 post-menopausal North American women. They examined the relationship between roughly half a dozen health-related traits and the number of children a women had, adjusting for things like income and education and assessing the way the traits might affect one another. The result indicates that humans are still evolving; as best I can gather, the idea is that certain heritable traits are likely to appear in greater numbers in future generations. On the basis of this information, several predictions can be made about the way natural selection is shaping the future of the human species (the female half of it, anyway).
To me, the interesting thing about this is the demonstration that we’re an evolving animal just like all the other evolving animals on the planet. The senior author of the study says we’re “kind of average” in the speed with which we evolve. It might not sound like a big deal, but the idea that current humans are not an end product but rather a snapshot in a long process goes against some deeply ingrained cultural assumptions. Even if you totally accept the truth of evolution and understand at some level how it works, it can be hard to really understand that the concept of “human” (or any other species) is provisional and time-dependent. (I thought of this when I saw the Ardipithecus show on Discovery last weekend, in particular regarding the idea that “humans evolved from chimps” versus the more precise statement that both evolved from a common ancestor, and the question of how exactly to categorize each group of animals during that process of evolution.)
This story from Medical News Today and this one from Science Daily have more information. The work is reported as Natural Selection in a Contemporary Human Population, by S.G. Byars et al. Proceedings of the National Academy of Sciences 107(suppl1), 1787–1792, 2010. doi: 10.1073_pnas.0906199106.
