What do resistance to malaria and light skin have in common? These two human characteristics, along with many others, developed in the past 10,000 years. Many people believe humans stopped evolving with the rise of culture. However, assistant professor of anthropology John Hawks has another controversial idea: human evolution is accelerating.
The first modern humans originated in Africa 50,000 years ago, says Hawks. About 5,000 years ago culture arose, which brought about changes for early humans, and many think the end of human evolution.
""The idea is that because we are culturally sophisticated we can improve our environment and make us better survivors,"" said Hawks. ""It's true that by cultural means we make some aspects of our existence easier. But we actually make other parts more complicated.""
Hawks completed his undergraduate degree at Kansas State University, and his M.A. and Ph.D. at the University of Michigan. He has been an associate professor in anthropology at UW-Madison since 2002. His work was recently featured in ""Discover Magazine"" and ""The Best American Science Writing 2010.""
Hawks studies genes to determine which in particular have been targets of natural selection. These selective pressures did not vanish when culture arose, he said, they were just different.
Diet is an excellent example of this. When humans became farmers, they altered the land, creating new homes for mosquitoes carrying malaria. Early humans had to adapt to that new selective pressure.
""Malaria resistance genes evolved in Africa in the past 5,000-10,000 years because malaria started to become a real problem when people became agriculturalists,"" said Hawks. ""So you have that correlation with the way history unfolded and the environment.""
Human evolution is a controversial topic because many experts believe it stopped with the emergence of modern humans.
According to ""The Best American Science Writing 2010,"" Leda Cosmides and John Tooby, founders of evolutionary psychology, believe the human brain has barely changed in 50,000 years.
Hawks demonstrates this rapid acceleration by pointing to how far humans have come since they first arose in Africa. He does this by studying the genes of an extinct group of people, the Neanderthals.
""We have the genetics of an extinct group of people, and we can show that there's not very much that we have that they don't,"" said Hawks. ""The fact that we haven't changed much as a species helps to illustrate that since we have different populations of humans—Europeans, Africans, Australians—we have changed a lot.""
What Hawks is getting at is that different ethnic groups are a direct result of accelerating human evolution. Humans started migrating out of Africa and these different environments selected for different traits, he explained.
One example is skin color. When humans migrated north into Europe they did not receive as much sunlight as they did in Africa. This became a problem since humans need sunlight to make vitamin D, which is essential for bone development. This new selective pressure resulted in lighter skin.
Since cultural differences can be traced back to genetics, many people want to keep these findings quiet rather than run the risk of genetic discrimination. But Hawks counters that this information needs to be public knowledge.
""I think the reason that a lot of people are reluctant to talk about human variation is that if you show that the difference between two people is rooted in their genetics, then you can't alter it,"" he said.
Today, Hawks is looking for genes that have been reoccurring targets for change, such as diet and disease resistance. He believes that if current trends continue, the human population will grow closer genetically, rather than farther apart.
There is no doubt in Hawks' mind that human evolution is accelerating. But why?
""Two reasons,"" he said. ""We're changing our environment faster, and there are more of us. That's all it is.""
For more information about Hawks' research visit his blog at johnhawks.net/weblog.
