....People, including this science journalist, tend to emphasize biology when thinking about human evolution, but that focus contains an element of looking-for--my-keys-under-the-streetlight reasoning. Genetic evolution can be rigorously measured and quantified. Cultural evolution is messy and difficult to study in journal-appropriate ways, yet in many ways culture -- our social practices and institutions, including the all-important vehicle of language -- is more powerful than biology.
After all, if we could travel back in time a few hundred thousand years, Homo sapiens would be quite recognizable. It's culture that truly distinguishes us.
In the last decade, researchers have developed tools for studying cultural evolution, from patterns of linguistic change to folktale relatedness (above) to interpretations of Polynesian canoe design. As with biological evolution, cultural evolution is clearly continuing: The advent of digital communications technologies, for example, makes new types of cultures possible.
For now, though, an Origin of Species for cultural evolution hasn't yet been written.