Did an ice age boost human brain size? Or a magnetic reversal?

“Why did we humans evolve such big brains, making us the unrivalled rulers of the world?” asks this article in New Scientist.

29 Jul 09 – “Some 2.5 million years ago, our ancestors’ brains expanded from a mere 600 cubic centimetres to about a litre. Two new studies suggest it is no fluke that this brain boom coincided with the onset of an ice age.”

Biologists David Schwartzman and George Middendorf of Howard University hypothesize that our modern brain could not have evolved until the Quaternary ice age started, about 2.5 million years ago, because such a large brain would have generated heat faster than it could dissipate it in the warmer climate of earlier times.

If keeping cool is a problem now, says climate researcher Alex Kleidon of the Max Planck Institute for Biogeochemistry in Jena, Germany, it would have been too challenging 2 or 3 million years ago when temperatures were a few degrees warmer than today.

I don’t think the change to a larger brain had anything to do with the ice age.

If magnetic reversals trigger ice ages (as I claim in “Not by Fire but by Ice”), and if the Quaternary ice age started in sync with a magnetic reversal (as I show in “Not by Fire but by Ice”), then it seems logical that the radioactivity dumped onto our planet during the reversal would have caused mutations. Those mutations would explain the sudden appearance of our bigger brains.

By the way. Did you notice that it was a few degrees warmer back then than it is today? I wonder who caused that “global warming”?

See entire article by Bob Holmes
http://www.newscientist.com/article/mg20327194.000-
did-an-ice-age-boost-human-brain-size.html

Thanks to Winona Campbell for this link


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