Now, here's where it gets interesting. The actual human population at the moment is over 7 billion, but the effective population is estimated to be just 10,000! This shows an incredible lack of genetic diversity in our numbers; compare that to chimps who have an actual population of roughly 200,000 individuals and an effective population of 20,000. So what does this mean? It seems to point to a period of time in our past when we faced extinction. By following certain genetic clues in the DNA scientists are able to estimate when this event occurred and how many people were alive at the lowest point. There was apparently one close call around 70,000 years ago which may have left just 2000 humans survivors! There is also evidence for population bottlenecks which occurred around a million years ago; one, as our ancestors left Africa, and another as they attemped to cross the Bering land bridge.
More recently, during the agricultural revolution 10,000 years ago, our decimated numbers began to rebound, carrying with them the stamp of our brush with extinction. And scientists have very recently discovered that there are many new rare genetic variants in the human population that, given enough time, will introduce more diversity into our species, so...a bit of good news there I guess.
Anyway, cool stuff, It's amazing to me that our DNA can tell such a story.
http://www.nature.com/scitable/topicpage/genetic-drift-and-effective-population-size-772523
http://www.the-scientist.com/?articles.view/articleNo/27922/title/Ancient-humans-more-diverse-/
Well we're not as badly off as the cheetahs, whose effective population may have been in double digits at one stage (going by their genetic whatever).
ReplyDeleteThings don't look good for the cheetah; they are just too highly specialized in their genetic whatever. I think we should let them have Australia where they will not have to compete with other large cats.
ReplyDeleteMaybe we should let everyone rare have Australia. Too weird to live, too rare to die.
ReplyDelete