Gene Expression

Apocalypse 73,000 B.C.

FuturePundit points me to a new paper on the Toba explosion, Environmental impact of the 73 ka Toba super-eruption in South Asia:

The cooling effects of historic volcanic eruptions on world climate are well known but the impacts of even bigger prehistoric eruptions are still shrouded in mystery. The eruption of Toba volcano in northern Sumatra some 73,000 years ago was the largest explosive eruption of the past two million years, with a Volcanic Explosivity Index of magnitude 8, but its impact on climate has been controversial. In order to resolve this issue, we have analysed pollen from a marine core in the Bay of Bengal with stratified Toba ash, and the carbon isotopic composition of soil carbonates directly above and below the ash in three sites on a 400 km transect across central India. Pollen evidence shows that the eruption was followed by initial cooling and prolonged desiccation, reflected in a decline in tree cover in India and the adjacent region. Carbon isotopes show that C3 forest was replaced by wooded to open C4 grassland in central India. Our results demonstrate that the Toba eruption caused climatic cooling and prolonged deforestation in South Asia, and challenge claims of minimal impact on tropical ecosystems and human populations.

The Toba caldera is in Sumatra, but the ashfall in India was on the order of 15 centimeters to 6 feet. This might also be relevant to human evolution, The super-eruption of Toba, did it cause a human bottleneck?.

Citation Martin A.J. Williamsa, Stanley H. Ambroseb, Sander van der Kaarsc, Carsten Ruehlemannd, Umesh Chattopadhyayae, Jagannath Pale and Parth R. Chauhanf, Environmental impact of the 73 ka Toba super-eruption in South Asia, doi:10.1016/j.palaeo.2009.10.009


  1. #1 Bob Sykes
    November 24, 2009

    Isn’t there also an alleged Cheetah bottleneck dated to about the same time?

  2. #2 Paul Jones
    November 24, 2009

    Bottle neck suggests to me a larger more diverse population becoming a smaller less diverse population.

    If grit and intellectual adaptiveness needed to survive sudden climate change were heritable, we might be able to find those genes by comparing pre and post Toba gene pools.

  3. #3 Onkel Bob
    November 25, 2009

    15 centimeters to 6 feet or about 6 inches to 180 centimeters…

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