In my "Atlantic article on the genetic roots of stable-versus-reactive temperaments, I noted that the key gene variants linked to these traits appeared to have developed over only the last 50,000-100,000 years -- a short time in evolutionary time. That same idea is developed in Cochran and Harpending's "The 10,000-year Explosion." Here Razib at Gene Expression looks at polymorphisms that have developed over the last 10,000 years in response to agriculture.
Changes in human diet driven by cultural evolution seem to be at the root of many relatively recently emerged patterns of genetic variation. In particular, lactase persistence and varied production of amylase are two well known cases. Both of these new evolutionary genetic developments are responses to the shift toward carbohydrates over the last 10,000 years as mainstays of caloric intake.