-- Robert Preidt
THURSDAY, Feb. 23 (HealthDay News) -- Rising global temperatures
appear to have caused the earliest known horse to shrink in size,
new research indicates.
Sifrhippus first appeared in the forests of North America
more than 50 million years ago, it weighed about 12 pounds.
The horse lived during the 175,000-year period of time called
the Paleocene-Eocene Thermal Maximum, during which average global
temperatures rose by about 10 degrees Fahrenheit. This temperature
increase was caused by the release of huge amounts of carbon into
the atmosphere and oceans.
During this period of global warming, about one-third of mammal
species experienced significant reductions in size, researchers
Fossilized teeth show that
Sifrhippus shrank from about 12 pounds to about 8.5 pounds (a
30 percent reduction) during the first 130,000 years of the time
period and then rebounded to about 15 pounds in the final 45,000
years of that era.
The findings offer new evidence of the cause-and-effect
relationship between temperature and body size, and also offer
clues to how animals might be affected by rising global
temperatures in the near future, according to study leaders Ross
Secord of the University of Nebraska-Lincoln and Jonathan Bloch of
the Florida Museum of Natural History at the University of Florida
In the study, published in the Feb. 24 issue of the journal
Science, the scientists performed an analysis of the oxygen isotopes in the fossilized teeth of Sifrhippus.
The results were "absolutely startling," according to Bloch. "We
looked at the curve and we realized that it was exactly the same
pattern that we were seeing with the horse body size."
He explained that for the first time, "going back tens of
millions of years -- we were able to show that indeed temperature
was causing essentially a one-to-one shift in body size within this
lineage of horse. Because it's over a long enough time, you can
argue very strongly that what you're looking at is natural
selection and evolution -- that it's actually corresponding to the
shift in temperature and driving the evolution of these horses,"
Bloch said in a University of Nebraska-Lincoln news release.
Secord added: "This has implications, potentially, for what we
might expect to see over the next century or two, at least with
some of the climate models that are predicting that we will see
warming of as much as 4 degrees Centigrade (7 degrees Fahrenheit)
over the next 100 years."
Scientists studying birds have already started to notice a
possible decrease in birds' body size, Secord noted in the news
"One of the issues here is that warming [during the Paleocene-Eocene Thermal Maximum] happened much slower, over 10,000 to 20,000 years to get 10 degrees hotter, whereas now we're expecting it to happen over a century or two," Secord said. "So there's a big difference in scale and one of the questions is, 'Are we going to see the same kind of response?' Are animals going to be able to keep up and readjust their body sizes over the next couple of centuries?"
The Florida Museum of Natural History offers a
fossil horse cybermuseum.
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
Copyright © EBSCO Publishing. All rights reserved.