Though it's often difficult for us to envision how natural selection actually affects modern human populations, I've found some hard evidence that human populations are indeed still evolving.
A study recently published in Nature Genetics reports findings of recent human evolution which "reveal one of the most striking genetic footprints of natural selection ever observed in humans."
Sara Tishkoff, a researcher from the University of Maryland, found that human populations in Africa developed the ability to digest milk through a mutation which occurred sometime in the past few thousand years. Not all human ethnic populations are able to digest milk through adulthood - only Northern Europeans, whose ancestors domesticated catte, and East African populations that herd cattle. However, until Tishkoff's study, it was unclear how African populations developed this ability, since their genomes do not contain the same mutation that allows Europeans to digest lactose.
By resequencing DNA samples from a number of ethnic groups in Africa, Tishkoff found a mutation in cattle-herding populations that allowed those populations to digest milk that was distinct from the European mutation.
In both European and African populations, the mutation for lactose tolerance appeared at roughly the same time that cattle domestication became prevalent in those populations. Tishkoff's study thus provides an interesting example of how genes and cultures co-evolve.
You can read the article here to learn more about this study:
The actual Nature Genetics paper should be accessible from this website:
I wrote an Amazon review, though it's not showing up quite yet. When it does, it will be with all the other Amazon reviews for the first book that comes up when you search for "autobiography of charles darwin" on Amazon.com