24 Feb 2012

Horses the size of small dogs were common for 50 million years

For more than 50 million years, was much more heat in the earth and horses, to adapt to these temperatures werealmost the size of small dogs, wandering the forests of North America, according to a study published on Thursdayby Science magazine.

These earliest known horse called Sifrhippus actually become smaller over tens of thousands of years, an age in which methane emissions have soared, possibly due to large volcanic eruptions. And the research could contribute to the knowledge of how modern animals on the planet can adapt to global warming.To reach this result, the scientists analyzed fossil teeth of horses found in Wyoming (northwest).Many animals have become extinct during this period of 175,000 years in length, known as the Thermal Maximum of the Paleocene-Eocene, which occurred 56 million years ago. Others decreased in size to survive with limited resources.According to a study author, Jonathan Bloch, of the Natural History Museum of Florida (Southeast), the average world temperatures rose 10 degrees Fahrenheit during this period due to the significant increase of carbon dioxide emitted into the air and oceans.The sea surface temperature in the Arctic was then 23 degrees centigrade, as the subtropical waters of the contemporary.The research showed that Sifrhippus fell by almost a third, until you reach the size of a small dog (four pounds) for the first 130,000 years of the period. Then he began to grow again until you get to seven pounds in the last 45,000 years of the period. Approximately one third of known mammal also become smaller during this time.
According to researchers, observing the reaction to climate change Sifrhippus of his time has major questions about how modern mammals respond to global warming today, what is happening much faster. By current estimates, the Earth's average temperature could rise by four degrees Celsius in just a century against the thousands of years it took to reach a level similar in Paleocene-Eocene.
"We estimate that about a third of mammals shrink in size and some will be very small, with up to half his original body weight," says Ross Secord, University of Nebraska and lead author of the article in "Science". "As warming occurred much more slowly during the PETM, the mammals had more time to adjust the size of their bodies. Thus, it is unclear whether we will see the same thing happen in the near future, but it is quite possible. There is a huge difference scale between the two heating which raises questions as' animals able to keep pace with climate change and readjust the size of their bodies over the next two centuries? "

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