April 24, 2008

Humans nearly went extinct 70K years ago, scientists claim.

This is all based on genetic data, and I don't understand it a bit, but it's very interesting. It brings to mind the cross-cultural stories of big disasters that nearly wiped us out, like Noah and the flood. One wonders if we had some sort of cultural memory of this?

posted by meredithea 16 years ago
  • My father participated in a DNA study similar to this (mostly to aid in his genealogy hobbies). One of the results was a map of the major migration groups out of Africa showing which one our ancestors were a part of.
  • Fools. Humans DID go extinct 70K years ago. We`are all monkeys.
  • Well "Thank God!" we didn't. Hyuck, yuck, yuck, yuck!
  • Fools. Humans DID go extinct 70K years ago. We`are all monkeys Golgafrinchans. FTFY
  • That was actually already the second time we nearly went extinct. But now, the third time, we're going to really do it!
  • die off
  • Didn't we see this report doing the rounds last year, or perhaps the year before? I thought when I read it, 'hang on, I've already read about this somewhere.'
  • No record of population density can persist in DNA, which is merely available for qualitative analysis. Only a quantitative analysis of rich fossil beds could provide any sense of how many people actually lived 70 thousand years ago. And times of drought make for a poor fossil record. For example, that's why cactus fossils are so rare even though we see a lot of them growing today in arid regions. It's a romantic notion that we almost became extinct, but until somebody finds enough fossils to support the claim, let's just make the movie.
  • Well, fossilization is a rare process, and there is never going to be guaranteed a fossil cache relevant to any particular line of inquiry. But it seems to me that this analysis of the mitochondrial DNA is entirely analogous to fossil study, in that we know how it behaves & is passed down. Because the rate of variation in mtDNA in a given population can be calculated, and because our mtDNA shows a marked lack of variation dating to roughly this point in history, it does tend to suggest fairly strongly that the overall human population dropped precipitously right then. It doesn't seem to be an invalid deduction.
  • Thanks for the elucidation, Hank. I still wonder though if people's rate of genetic variation isn't sometimes precipitous, like the *punctured equilibrium* we hear about, from Stephen Gould, for example
  • Er... What I'm wondering, on the other face of it then, is whether there might be an opposite effect, and people didn't change much for a time even though there were a lot more people extant.
  • But when the mtDNA changes finally DID come, I see now that the most reasonable assumption is that this probably that couldn't happen to a lot of people at once. Interesting!
  • Somebody urgently needs to do a good job of back-forming an intransitive verb out of 'extinct' to save all this 'go extinct' and 'become extinct' business. It ought to be 'Humans nearly extinguished 70k years ago', but I can't see that catching on.
  • Hey, not to worry, there's another chance coming along for us to get extincted.