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Humans Nearly Went Extinct 1.2M Years Ago
Hugh Pickens writes "Scientific American has a story on researchers from the University of Utah who have calculated that 1.2 million years ago, at a time when our ancestors Homo erectus, H. ergaster, and archaic H. sapiens were spreading through Africa, Europe, and Asia, there were probably only about 18,500 individuals capable of breeding in all these species together (PNAS paper here). Pre-humans were an endangered species with a smaller population than today's gorillas and chimpanzees. Researchers scanned two completely sequenced modern human genomes for a type of mobile element called Alu sequences, then compared the nucleotides in these old regions with the overall diversity in the two genomes to estimate differences in effective population size, and thus genetic diversity between modern and early humans. Human geneticist Lynn Jorde says that the diminished genetic diversity one million years ago suggests human ancestors experienced a catastrophic event at that time as devastating as the Toba super-volcano in Indonesia that triggered a nuclear winter and is thought to have nearly annihilated humans 70,000 years ago."
I think this means we are a stubborn infestation, successfully resisting the Universe's attempts to exterminate us thus far. The Universe realized that we are harder to kill than cockroaches, and concluded that the only way to wipe us out is to place the means of our destruction in our own hands. Now, it's just a waiting game.
I prefer rogues to imbeciles because they sometimes take a rest.
The DNA that creates different physical traits does mutate in (more or less) unpredictable leaps and bounds as time goes on. But that's not the DNA they look at in cases like this. There's long strings of junk DNA that does nothing at all - random leftover of mutations that didn't happen to affect our survival one way or the other. Because these don't affect physical traits, they aren't selected for or against and are subject to only one 'force', genetic drift. That's why they're fairly constant.
More than that, I read a year or so ago (it may have been covered at slashdot, I don't remember) that it was mathematically proven that everyone on earth shares common anscestors from as little as a thousand years ago.
Besides, there was the other near extinction 70K years ago. Wht I find interesting is the near extinctions were probably what led to modern humans' intelligence and other traits (like humor) that makes us so different from other species.
Free Martian Whores!
I disagree. I think you'd see the same correlations in some species, but not necessarily all.
Let's posit some kind of catastrophic event that puts pressure on early hominids. It does not follow that every species is put under evolutionary pressure, only those that rely on the certain ecological resources to survive. So it doesn't have to be an event like nuclear winter.
Furthermore we might not see these effects in other species because most of the species that survived found the changes brought on by the event favorable to them. The ones that didn't for the most part may not have survived, or may have only survived in certain niches.
Hominids are a special case. Except in a few circumstances migration is not part of their lifestyle, but they have a tremendous latent capacity to migrate, probably greater and certainly more flexible than any land animal. So our posited "disaster" happens, but it doesn't look like a disaster to most of the species that survived. As for those for whom it was a disaster, many perish and a few manage to hold on in isolated geographic niches. These are almost certain to include hominids, with their adaptability and latent capacity to migrate great distances. Most of the hominids either don't get moving quickly enough or don't find a place to survive in, but enough of them do to maintain a breeding population.
Of course, this scenario isn't a scientific one. It's more of a counterscenario demonstrating that we wouldn't necessarily expect to see the same genetic phenomena everywhere we looked.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
The flood story is most likely a composite of semi-historical and mythological events surrounding the flooding of the Tigris and Euphrates rivers. It may also be related to the flooding of the Persian Gulf at the end of the last glacial period, when trillions of gallons of sea water flooded into what was a very large (and possibly very fertile) valley. Since the destruction caused by this event, and the resulting 10,000 years of salt-water erosion, would've wiped out any sign of an ancient hunter-gatherer or subsistence civilization in what is now the Persian Gulf, it's impossible to prove. But it's still fun to speculate.
God invented whiskey so the Irish would not rule the world.
The TWO (only two) genomes analyzed were from the subpopulation which left Africa. If you fully sequence a native south African more genomic variety, this hypothesis may not hold up.
But, the effect was spread on all H. Sapiens level species more or less equally, giving the more adaptable group the advantage of a sparse landscape. If the near-extinction event hadn't happened, H. Sapiens would likely have been out competed by entrenched specialists.
Not that it truly matters. There are roughly 27 states in which you can marry your FIRST cousin. To many, this seems "sick" because of the social implications it presents (100 years ago, you'd be fortunate to see some first cousins once or twice in your lifetime. Now it is common to see most of them several times a year, along with any other common relatives). However, you are genetically diverse enough from your first cousin that there are no genetic problems, other than sharing undesirable, recessive, genetic diseases.
"When life gives you lemons, don't make lemonade. Make life take the lemons back!" -- Cave Johnson
Have you heard of the Black Sea Deluge Theory?, basically, they found ruins at the BOTTOM of the Black Sea. Combined with geological records, many speculate that there was a single, massive Flood in the area that wiped out entire cities. This could be the basis for Noah's flood.
Bah, you call that news? Try:
"Humans Nearly Went Extinct 27 Years Ago"
the commander's Wikipedia entry says he:
You can follow any of the links in the above search, or here's a particularly lively read.