My favorite foods all seem to involve lactose. Whether it's an aged goat cheese from the Loire Valley, or a stinky washed rind cheese, or a scoop of dark chocolate ice cream, I would probably starve if I was lactose intolerant. Now we know how lactose-tolerance evolved. Being able to digest milk is such a beneficial mutation that it appears to have evolved independently three different times:
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.
Throughout most of human history, the ability to digest lactose, the principal sugar of milk, has been switched off after weaning because the lactase enzyme that breaks the sugar apart is no longer needed. But when cattle were first domesticated 9,000 years ago and people later started to consume their milk as well as their meat, natural selection would have favored anyone with a mutation that kept the lactase gene switched on.
Comments (5)
You state: "Whether it's an aged goat cheese from the Loire Valley"
However, most problems with lactose intolerance relate specifically to the sugar molecule of the cow...goat and sheep milk have smaller sugar molecules that are easier to break down and digest, and are much closer to the human's. For instance, while I have pretty bad lactose intolerance (which makes me curl up for about an hour in the fetal position in nauseous pain), I often enjoy sheep yogurt and goat and sheep cheese (in fact, I find most cow cheese extremely boring flavored anyway, so it is no big loss).
Posted by: Bryan | December 11, 2006 2:35 PM