Tonight, the Perpetual Notion Machine digs into our archive of shows to rebroadcast an edited version that originally aired on January 17, 2008. Our guest was John Hawks, anthropologist and evolutionist at UW-Madison. With his research into various genetic sequences of the human genome and at times, the use of some convenient mummified DNA, he has identified the rate of human evolution, at least for a few specific genetic traits. John described several ways the rate of evolution can be measured. One way is to determine about when a new trait or genetic mutation occurs, how often it occurs, and when the mutation becomes common throughout the population. This is the essence of natural selection. One example that John described is the lactase gene, which enables a human to digest lactose, or the sugar in milk. This gene seems to have suddenly appeared about 8,000 years ago, coinciding with the agricultural practice of raising dairy animals like cows, sheep, and goats. This ability to digest the sugar in milk gives the human body a boost in energy for a longer survival pattern in the population, but only these isolated populations. Today, about 20% of the total population have this ability. But in terms of geologic time, this specific genetic evolution is pretty fast!