[Dean's World] Dave Price: The Toba Catastrophe

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Posted by Dave Price:
The Toba Catastrophe
http://www.deanesmay.com/posts/1198859858.shtml


   Is [1]this why [2]humans have relatively little genetic variance
   compared to most species?

     Geneticists Lynn Jorde and Henry Harpending of the University of
     Utah proposed that the variation in human DNA is minute compared to
     that of other species. They also propose that during the Late
     Pleistocene, the human population was reduced to a small number of
     breeding pairs â no more than 10,000 and possibly as few as 1,000 â
     resulting in a very small residual gene pool. Various reasons for
     this hypothetical bottleneck have been postulated, one of those is
     the Toba catastrophe theory.
     ...
     According to the Toba catastrophe theory, 70,000 to 75,000 years
     ago a supervolcanic event at Lake Toba, on Sumatra, reduced the
     world's human population to 10,000 or even a mere 1,000 breeding
     pairs, creating a bottleneck in human evolution. The theory was
     proposed in 1998 by Stanley H. Ambrose of the University of
     Illinois at Urbana-Champaign.
     Within the last three to five million years, after human and other
     ape lineages diverged from the hominid stem-line, the human line
     produced a variety of species.
     ...
     According to the Toba catastrophe theory, a massive volcanic
     eruption severely reduced the human population. This may have
     occurred around 70â75,000 years ago when the Toba caldera in
     Indonesia underwent an eruption of category 8 (or "mega-colossal")
     on the Volcanic Explosivity Index. This released energy equivalent
     to about one gigaton of TNT, which is three thousand times greater
     than the 1980 eruption of Mount St. Helens. According to Ambrose,
     this reduced the average global temperature by 5 degrees Celsius
     for several years and may have triggered an ice age.

   When I read theories like this, it always brings to mind the [3]Drake
   equation and the [4]weak anthropic principle, and makes me wonder just
   how incredibly unlikely a chain of coincidences we rode on the path to
   intelligence.

References

   1. http://en.wikipedia.org/wiki/Toba_catastrophe_theory
   2. http://en.wikipedia.org/wiki/Humans
   3. http://en.wikipedia.org/wiki/Drake_equation
   4. http://en.wikipedia.org/wiki/Weak_anthropic_principle