September 19th, 2011
Episode 92 of 571 episodes
In the second episode of this three-part series, geneticist and broadcaster Adam Rutherford explores the complex and sometimes controversial world of human evolution. He talks to geneticists, evolutionary psychologists and anthropologists to try and understand and untangle the relationship between our biology, our genes and our cultural and social behaviour. Have we, as Professor Steve Jones thinks, evolved beyond evolution by natural selection? He thinks that in the western, developed world, the normal driving force for evolution by natural selection is tailing off. We are all having a similar number of babies and those children are surviving and having children of their own. The impact of this is that there's no longer an opportunity for genes which may be beneficial to be selectively passed on. As these trends increase, he says that "if we haven't already stopped evolving, we soon will." Seeing evolution in action isn't easy, by its very nature, it only occurs on a generational time-scale. But there is evidence of very recent human evolution, some of which may still be occurring now - particularly fueld by disease epedemics, from flu to HIV. Since the human genome was decoded, geneticists are finding regions of genetic code which are relatively stable amongst populations - the so called "Darwin's Fingerprint" - evidence that these genes have been selected for and passed on, in the past. Examples of these include genes for lactose tolerance, which evolved in dairy herders, as recently as 3000 years ago, and is thought to still be spreading as the world switches to a dairy-rich diet. Disease-resistance is also seen in our genomes, as is apparent increases in the length of time women are able to have babies. But, Kevin Laland, at St Andrews University says we're not just passive actors in our genetic destiny. In fact it's our ability to change our environment which not only drives out cultural evolution, but has a direct effect on our genes as well.