Pint-sized primates were first in North America

Beach bums
The coastlines of North America afforded certain advantages to the small primates. For instance, during the Paleocene-Eocene Thermal Maximum, the coastlines became hot and wet, while the Rocky Mountain region became hot and dry. The dry conditions would not have supported the lush trees and their yummy fruits required for Teilhardina and other closely related primates.

Beard found that Teilhardina magnoliana from Mississippi is both older and more primitive than another Teilhardina species previously found in Wyoming's Bighorn Basin. Since the fossil record at Bighorn is remarkably complete, Beard is confident that fossils older than those unearthed in Mississippi would have been found by now if they existed.

That means the earliest North American primates were restricted to coastal regions for thousands of years before they were able to colonize the Rocky Mountain region.

Later, precipitation would have increased to make Wyoming and other Rocky Mountain regions hospitable to the little primates.

Chill out
Though Teilhardina once occupied parts of the United States for tens of thousands of years, none of its distant relatives, such as monkeys, currently live here.

That's because most primates are adapted to live only in wet, humid tropical or subtropical regions. When Earth began cooling at the end of the Eocene about 35 million years ago, Teilhardina vanished from North America and Europe, Beard said.

Modern humans obviously are adapted to live in a variety of climates today, but at that time, warmer regions were critical layover spots for our primate ancestors. Lucky for us, Beard says, some of these ancestors in the late Eocene had set up camp in warmer climes.

"You and I wouldn't be here talking about it if it weren't for the fact that primates by this time were able to colonize Central Africa and Southeast Asia," Beard told LiveScience. "As far as we know, those were the only two places that primates were able to survive this dramatic cooling event 35 million years ago."

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