Researchers at Harvard have found data setting the origin of ants at 140 to 168 million years ago, making them millions of years older than scientists previous thought.

A team co-led by Corrie S. Moreau, a doctoral candidate in organismic and evolutionary biology at Harvard, has published the first large-scale study of ants based on DNA to make an ant family tree, showing how different ant species are related. A little known subterranean subfamily, Leptanillinae, was discovered to be the most ancient relative of modern-day ants. “Until our study, the phylogenetic relationships of the ants was not resolved,” wrote Moreau in an e-mail.

Fossils were then used in conjunction with a molecular clock to discover the origin of modern ants and their times of diversification. This research indicated that ants originated long before scientists had believed. The current oldest known fossil of an ant dates back 135 million years.

The pattern of evolution suggests the ant family tree began to split with the advent of flowering plants, 100 million years ago, as ants adapted to newly-emergent environments.

“Our results support the hypothesis that angiosperm forests and their associated insect herbivores expanded the range of ecological opportunities available to ants, leading to their diversification and dominance in almost all terrestrial ecosystems,” said Moreau.

Research for the project was made possible by funding from Harvard’s Green Fund, administered by evolutionary biologist E. O. Wilson, and the National Science Foundation. In addition to Moreau, researchers on the study also included Roger Vila and S. Bruce Archibald from the Museum of Comparative Zoology, as well Hessel Professor of Biology Naomi E. Pierce. Charles D. Bell from Florida State University was also a member of the research team.