[asa] Early primates' dispersal driven by ancient global warming

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Ancient global warming drove early primates' dispersal
Public release date: 25-Jul-2006 Contact: Nancy
Ross-Flanigan rossflan@umich.edu 734-647-1853 University of Michigan
http://www.eurekalert.org/pub_releases/2006-07/uom-agw072506.php

Ann Arbor, Mich. -- The continent-hopping habits of early primates
have long puzzled scientists, and several scenarios have been
proposed to explain how the first true members of the group appeared
virtually simultaneously on Asia, Europe and North America some 55
million years ago.

But new research using the latest evidence suggests a completely
different migration path from those previously proposed and indicates
that sudden, rapid global warming drove the dispersal.

Researchers from the University of Michigan, Johns Hopkins University
School of Medicine and the Royal Belgian Institute of Natural
Sciences present their findings in the July 25 issue of the
Proceedings of the National Academy of Sciences.

Their work focuses on Teilhardina, an ancient genus that resembled
the saucer-eyed, modern-day primates known as tarsiers. Like
tarsiers, monkeys, apes and humans, Teilhardina was a true primate,
or euprimate. In both Asia and Europe, the genus is the oldest known
primate; in North America, it appears in the fossil record around the
same time as another primate, Cantius. Previously, scientists had
come up with four ways to explain the geographic distribution pattern.

The first is that primates originated in Africa and spread across
Europe and Greenland to reach North America. Another possibility is
that they originated in North America and traveled across a temporary
land bridge connecting Siberia and Alaska. A third hypothesis is that
primates had their origins in Africa or Asia and traveled through
North America to reach western Europe. Finally, it has been suggested
that the group originated in Asia and fanned out eastward to North
America and westward to Europe.

In the new research, U-M paleontologist Philip Gingerich and
coworkers re-evaluated the four hypotheses by comparing with
unprecedented precision the times of first appearance of Teilhardina
in Asia, Europe, and North America. To achieve such precision, they
used a carbon isotope curve recently documented on all three
continents. Carbon in the atmosphere, earth and living organisms
differs in the proportion of carbon-12 and carbon-13 present. A flood
of carbon-12 is associated with the onset of an event known as the
Paleocene-Eocene thermal maximum (PETM), one of the most rapid and
extreme global warming events recorded in geologic history. It was
during the PETM that modern primates first appeared 55 million years
ago. Teilhardina in Asia precedes the maximum flood of carbon-12,
Teilhardina in Europe coincides with it, and Teilhardina in North
America appears just after the maximum. Based on this evidence, the
researchers concluded that none of previously proposed scenarios was
likely. Instead, they propose that Teilhardina migrated from South
Asia to Europe, crossing the Turgai Straits---an ancient seaway
between Europe and Asia---and then spread to North America by way of Greenland.

The whole dispersal event happened within about 25,000 years.

"It is remarkable to be able to study evolutionary events so deep in
the past with such precision," said Gingerich, who is the Ermine
Cowles Case Collegiate Professor of Paleontology and director of the
U-M Museum of Paleontology. "The speed of dispersal and the speed of
evolutionary change during dispersal are near the maximum for such
rates observed today, and the rapid change and dispersal were almost
certainly driven by profound greenhouse warming at the
Paleocene-Eocene boundary."
###

Gingerich's coauthors on the paper are Thierry Smith of the Royal
Belgian Institute of Natural Sciences and Kenneth Rose of Johns
Hopkins University School of Medicine. The researchers received
funding from National Geographic Society, the Belgian Federal Science
Policy Office and the U.S. National Science Foundation.

For more information:

Philip Gingerich:
<http://www.ns.umich.edu/htdocs/public/experts/ExpDisplay.php?ExpID=293>http://www.ns.umich.edu/htdocs/public/experts/ExpDisplay.php?ExpID=293

Proceedings of the National Academy of Sciences:
<http://www.pnas.org/>http://www.pnas.org/

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Received on Wed Jul 26 14:36:06 2006