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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."
The end result is the same as that predicted for nuclear winter. Radiation is not the primary danger from a "real" nuclear winter, it's the smoke and soot that would spread through the atmosphere, drastically reducing the amount of sunlight received at the surface, killing plants and reducing temperatures everywhere. When a supervolcano goes off, the effects are nearly identical.
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The 18500 people quoted is not the number of people capable of breeding, but the "effective population", an abstract measure of genetic diversity in a species. According to TFA, the effective population of modern humanity is about 10000, and the argument in the article is that this much lower diversity indicates that a lot of genetic material must have been lost in a near-extinction event.
Because 1.2 million is the same as 70,000, right? You must work for Goldman Sachs.
But why should we assume a uniform rate over time, when evolutionary theory says that genetic differentiation happens in leaps and bounds?
Sources should always be cited when making this kind of argument. I'll do it for you this time:
Pr. Charles Xavier, X-Men movie introduction speech
I don't expect them to use the term 'catastrophic clamactic event' in a flowing sentence.
Quite right. Such terms should be reserved for events like the 1912 San Francisco Shellfish Riots.
Linux, you magnificent bastard, I read the fucking manual!
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.
"I do not understand," reads an ancient line of pictographs depicting the sun, the moon, water, and a Sumerian who appears to be scratching his head. "A booming voice is saying, 'Let there be light,' but there is already light. It is saying, 'Let the earth bring forth grass,' but I am already standing on grass."
So... an alternate headline would be "Ancient Sumerian on grass hears voice of God".
The enemies of Democracy are
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.
We also have written evidence that Frodo set forth from the Shire in order to destroy the One Ring before it fell into the hands of Sauron. But so what?
So that's what 'Ribbed for Your pleasure' comes from!
Meep.