Featured Research

from universities, journals, and other organizations

Evolution of earliest horses driven by climate change

Date:
February 23, 2012
Source:
University of Nebraska-Lincoln
Summary:
Some 56 million years ago, rising temps and concentrations of carbon dioxide caused mammals, including tiny Sifrhippus, to shrink. New research offers new evidence of why and how it happened and provides clues to what might happen to animals in the future from global warming.

Upper jaw of the earliest known horse species (foreground) compared to the upper jaw of a modern-day horse.
Credit: Kristen Grace, University of Florida

When Sifrhippus, the earliest known horse, first appeared in the forests of North America more than 50 million years ago, it would not have been mistaken for a Clydesdale. It weighed in at around 12 pounds -- and it was destined to get much smaller over the ensuing millennia.

Sifrhippus lived during the Paleocene-Eocene Thermal Maximum, a 175,000-year interval of time some 56 million years ago in which average global temperatures rose by about 10 degrees Fahrenheit, caused by the release of vast amounts of carbon into the atmosphere and oceans.

About a third of mammal species responded with significant reduction in size during the PETM, some by as much as one-half. Sifrhippus shrank by about 30 percent to the size of a smallhouse cat (about 8.5 pounds) in the PETM's first 130,000 years and then rebounded to about 15 pounds in the final 45,000 years of the PETM.

Scientists have assumed that rising temperatures or high concentrations of carbon dioxide primarily caused the phenomenon in mammals during this period, and new research led by Ross Secord of the University of Nebraska-Lincoln and Jonathan Bloch of the Florida Museum of Natural History at the University of Florida in Gainesville offers new evidence of the cause-and-effect relationship between temperature and body size. Their findings also offer clues to what might happen to animals in the near future from global warming.

In a paper to be published in the Feb. 24 issue of the international journal Science, Secord, Bloch and colleagues used measurementsand geochemical composition of fossil mammal teeth to document a progressive decrease in Sifrhippus' body size that correlates very closely to temperature change over a 130,000-year span.

Bloch, associate curator of vertebrate paleontology at the Florida Museum of Natural History, said multiple trails led to the discovery.

One was the fossils themselves, recovered from the Cabin Fork area of the southern Bighorn Basin near Worland, Wyo. Stephen Chester, then an undergraduate student at Florida, now an anthropology Ph.D. candidate at Yale and a co-author on the paper, had the task of measuring the horses' teeth. What he found when he plotted them through time caught Bloch and Secord by surprise.

"He pointed out that the first horses in the section were much larger than those later on," Bloch recalled. "I thought something had to be wrong, but he was right -- and the pattern became more robust as we collected more fossils."

A postdoctoral researcher in Bloch's lab for the first year of the project, Secord performed the geochemical analysis of the oxygen isotopes in the teeth. What he found provided an even bigger surprise.

"It was absolutely startling when Ross pulled up the first oxygen isotope data," Bloch said. "We looked at the curve and we realized that it was exactly the same pattern that we were seeing with the horse body size.

"For the first time, going back into deep time -- going back 10s 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."

Secord, who came to UNL in 2008 as an assistant professor of Earth and atmospheric sciences and curator of vertebrate paleontology at the University of Nebraska State Museum, said the finding raises important questions about how plants and animals will respond to rapid change in the not-too-distant future.

"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," he said.

Those predictions are based largely on the 40 percent increase of atmospheric carbon dioxide levels (from 280 to 392 parts per million) since the start of the Industrial Revolution in the mid-19th century.

Ornithologists, Secord said, have already started to notice that there may be a decrease in body size among birds.

"One of the issues here is that warming (during the PETM) 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?"

Increased temperatures are not the only change animals will have to adapt to, Secord said. Greenhouse experiments show that increased atmospheric carbon dioxide lowers the nutritional content of plants, which he said could have been a secondary driver of dwarfism during the PETM.

Other co-authors on thepaper are Doug M. Boyer of Brooklyn College, Aaron R. Wood of the Florida Museum of Natural History, Scott L. Wing of the Smithsonian National Museum of Natural History, Mary J. Kraus of the University of Colorado-Boulder, Francesca A. McInerny of Northwestern University, and John Krigbaum of the University of Florida.

The research was funded by grants from the National Science Foundation, with additional support from UNL.


Story Source:

The above story is based on materials provided by University of Nebraska-Lincoln. The original article was written by Tom Simons. Note: Materials may be edited for content and length.


Journal Reference:

  1. R. Secord, J. I. Bloch, S. G. B. Chester, D. M. Boyer, A. R. Wood, S. L. Wing, M. J. Kraus, F. A. McInerney, J. Krigbaum. Evolution of the Earliest Horses Driven by Climate Change in the Paleocene-Eocene Thermal Maximum. Science, 2012; 335 (6071): 959 DOI: 10.1126/science.1213859

Cite This Page:

University of Nebraska-Lincoln. "Evolution of earliest horses driven by climate change." ScienceDaily. ScienceDaily, 23 February 2012. <www.sciencedaily.com/releases/2012/02/120223142630.htm>.
University of Nebraska-Lincoln. (2012, February 23). Evolution of earliest horses driven by climate change. ScienceDaily. Retrieved September 2, 2014 from www.sciencedaily.com/releases/2012/02/120223142630.htm
University of Nebraska-Lincoln. "Evolution of earliest horses driven by climate change." ScienceDaily. www.sciencedaily.com/releases/2012/02/120223142630.htm (accessed September 2, 2014).

Share This




More Plants & Animals News

Tuesday, September 2, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Snack Attack: Study Says Action Movies Make You Snack More

Snack Attack: Study Says Action Movies Make You Snack More

Newsy (Sep. 2, 2014) — You're more likely to gain weight while watching action flicks than you are watching other types of programming, says a new study published in JAMA. Video provided by Newsy
Powered by NewsLook.com
Get A Mortgage, Receive A Cat — Only In Russia

Get A Mortgage, Receive A Cat — Only In Russia

Newsy (Sep. 2, 2014) — The incentive is in keeping with a Russian superstition that it's good luck for a cat to be the first to cross the threshold of a new home. Video provided by Newsy
Powered by NewsLook.com
U.N. Says Ebola Travel Restrictions Will Cause Food Shortage

U.N. Says Ebola Travel Restrictions Will Cause Food Shortage

Newsy (Sep. 2, 2014) — The U.N. says the problem is two-fold — quarantine zones and travel restrictions are limiting the movement of both people and food. Video provided by Newsy
Powered by NewsLook.com
Sharks Off the Menu and on the Tourist Trail in Palau

Sharks Off the Menu and on the Tourist Trail in Palau

AFP (Sep. 2, 2014) — Tourists in Palau clamour to dive with sharks thanks to a pioneering conservation initiative -- as the island nation plans to completely ban commercial fishing in its vast ocean territory. 01:15 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

More Coverage


Earliest Horses Show Past Global Warming Affected Body Size of Mammals

Feb. 23, 2012 — As scientists continue developing climate change projection models, paleontologists studying an extreme short-term global warming event have discovered direct evidence about how mammals respond to ... read more
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins