Sunday, December 10, 2006
Milking Environmental Resources
Well, I've always known that I'm "more evolved" than most people. It turns out us lactose tolerant humans are recent improvements to the species. However, some of you are apparently trying to catch up, according to an article in the New York Times by Nicholas Wade. A surprisingly recent instance of human evolution has been detected among the peoples of East Africa. It is the ability to digest milk in adulthood, conferred by genetic changes that occurred as recently as 3,000 years ago, a team of geneticists has found.
The finding is a striking example of a cultural practice — the raising of dairy cattle — feeding back into the human genome. It also seems to be one of the first instances of convergent human evolution to be documented at the genetic level.
My own Irish-American background probably links me to the early cattle-raising people known as the Funnel Beaker culture, which flourished, in large part to their lactose tolerance, some 5,000 to 6,000 years ago in north-central Europe.
A research team led by Sarah Tishkoff of the University of Maryland has now found three new mutations in Africa, all independent of each other and of the European mutation.Genetic evidence shows that the mutations conferred an enormous selective advantage on their owners, enabling them to leave almost 10 times as many descendants as people without them. ...
The survival advantage was so powerful perhaps because those with the mutations not only gained extra energy from lactose but also, in drought conditions, would have benefited from the water in milk. People who were lactose-intolerant could have risked losing water from diarrhea ...
On behalf of my fellow advanced humans, we want the rest of you to know we're pulling for you.The principal mutation, found among Nilo-Saharan-speaking ethnic groups of Kenya and Tanzania, arose 2,700 to 6,800 years ago, according to genetic estimates ... This fits well with archaeological evidence suggesting that pastoral peoples from the north reached northern Kenya about 4,500 years ago and southern Kenya and Tanzania 3,300 years ago.
Two other mutations were found, among the Beja people of northeastern Sudan and tribes of the same language family, Afro-Asiatic, in northern Kenya.
