The world's oldest ant fossils have been discovered in Utah, Arizona and New Mexico, scientists announced Monday.
Fossils of ant nests from 150 million years ago - the Jurassic period - were found in 1995 and this year near Canyonlands and Arches national parks in Utah and on Navajo lands in the three states.The discovery was announced in Denver during the Geological Society of America's annual meeting.
Stephen Hasiotis, a geologist at the University of Colorado at Boulder, and Timothy Demko, a Colorado State University researcher, found about 50 of the ant nests.
Until now, the most ancient confirmed evidence of prehistoric ants were 80 million-year-old body fossils of worker ants from New Jersey, Siberia and Alberta, Canada, Hasiotis said.
There also have been unconfirmed claims of 110 million-year-old ant fossils from Australia, he said.
Some of the nests found in the Southwest are more than 5 yards wide and 3 yards deep, indicating they were occupied for decades or perhaps centuries. They include interconnected chambers and galleries.
"They had to be social in order to construct and maintain these networks, brood their eggs and larvae, and collect food for the colony."
He said the existence of highly social behavior 150 million years ago suggests ants first evolved even earlier, perhaps in the Triassic period 208 million to 245 million years ago.