Sunday, January 17, 2010

Microsatellites, mass extinctions, and .... mammoth-punk?

I don't really know about "mammoth-punk"; I went with alliteration.

Science fiction and science fiction romance embraces "steam punk" and "cyber punk". What would (or do) we call alternate history dating back 800 years, or 35,000 years or even 75,000 years?

Suppose for a moment that the theoretical Toba catastrophe never happened. This theory suggests that a massive volcanic eruption on Sumatra covered the Indian subcontinent in 16 centimeters of more of ash, compounded an ice age and reduced mankind to perhaps as few as 1,000 "breeding pairs" thus creating a "bottleneck" in human evolution.

By the way, this theory seems to be at odds with Spencer Wells's study of Y chromosomes in Central Asia (see article published in the December 2004 issue of Discover magazine) which latter appears to suggest that the first humans moved out of Africa about 50,000 years ago.

Suppose for another moment that Genghis Khan (800 years ago) and described by Discover contributor Robert Kunzig as "a prodigious fornicator" was impotent.

How might our world be different?

Apparently, Genghis Khan's breeding territory cut a broad swathe across Asia, from Iran to the sea of Japan, and he had a woman in every port (and village along the way) and 500 wives. Allegedly, there is a microsatellite ("a short, repetitious sequence of DNA in which the number of repetitions can change from one generation to the next") that appears to suggest that Genghis Khan's male descendants are all across his former empire.

Robert Kunzig's "The Hidden History Of Men" (about Wells's "Human Genome Diversity Project") is a fascinating article, illustrated with three excellent maps. I love maps for world-building and inspiration! One map shows Genghis Khan's stomping ground. Another shows where Spencer Wells and his team took blood samples from men. The best map of all looks like a tattoo on some guy's back and shows little flags with genetic markers, tracing mankind's migrations after leaving Africa.

This map on Wikipedia shows a mitochondrial-related migration map. Mitochondrial mapping relies on female chromosomes.

Scientists seem to agree that all of us originated in Africa. I'd like to think that some of us didn't, that some of us originated on another planet or were seeded here by an interstellar Genghis Khan. But why Africa? Why not South America, or Australia, or India, or France?

I asked Google "Why did mankind originate in Africa?" and found plenty of  How-and-why-we-now-know-that-we-did..." but if someone knows the Why of it, it's not at the top of the search results.

Was it because the Sahara back then (before life left the sea) was the perfect warm, shallow, primaeval soup?

Freshwater lakes.

There is a theory about why some people left Africa. Mega-Drought. Climate change! Paradoxically, there's also a theory that the Sahara desert will once again become lush and fertile as a result of global warming. is an absolute treasure trove of links, for those fascinated by our planet.

All the best,
Rowena Cherry

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