24 Feb 2012:
Warming Climate Caused
Early Horse Species to Shrink, Study Says
A new study suggests that the earliest known horse species shrank significantly in size over a 135,000-year span
as a consequence of a warming climate. Using geochemical testing and measurements of fossilized teeth dating back more than 50 million years, U.S. researchers found that a 30-percent decrease in the body size of the species, Sifrihippus sandae
, corresponded closely with changes in global temperatures. As the average global temperature rose by about 10 degrees F during the first 135,000 years of that period — known as the Paleocene-Eocene Thermal Maximum (PETM) — the early horse, which lived in the forests of North America, declined in size from about 12 pounds to about 8.5 pounds, presumably because a declining amount of available oxygen. According to the study, published in the journal Science
, the species regained much of its size during the final 45,000 years of the PETM, bulking up to about 15 pounds. Researchers say the so-called “dwarfing” phenomenon could provide insights into how animals will respond to a projected increase in global temperatures in the coming centuries. “One of the questions is, ‘Are we going to see the same kind of response?’” said Ross Secord, a researcher at the University of Nebraska-Lincoln.
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