Three scientists have uncovered fossilized bees' nests in Arizona that appear to be more than 200 million years old, forcing paleontologists to reconsider the evolutionary timetable of flowering plants.
"The old school of thought was that flowers brought about the bees," said Stephen Hasiotis, a geology doctoral student at the University of Colorado at Boulder. "It was probably the other way around."
More than 100 fossilized nests were found in northeastern Arizona's Petrified Forest National Park by Hasiotis and Russel Dubiel, of the U.S. Geological Society, and Tim Demko of Colorado State University.
The nests date to about 220 million years ago.
If they were made by bees and wasps, as Hasiotis and others believe, it would push back the known origin of social, pollinating insects by 140 million years.
Hasiotis presented the discoveries at a recent Geological Society of America meeting in Bozeman, Mont.
The development of flowering plants and pollinating insects has been closely tied for millions of years.
Scientists believed their evolution was synchronized, or perhaps the distribution of flowers prompted insect development.
Now, the fossil discovery, as well as several other fossil discoveries in the last two years, indicate that insects started the process.
The bees' nests also indicate that bees and wasps were social creatures more than 200 million years ago.
The previous earliest known bee-fossil evidence--found in New Jersey--was thought to be about 80 million years old, while wasp-fossil evidence found in Brazil was estimated at 16 million years of age.
The major doubt is whether the nests uniquely belonged to bees, because no fossilized insects were found in the nests, according to Kirk Johnson, a paleobotanist at the Denver Museum of Natural History.
Hasiotis said the nests are flask-shaped and have smooth walls. The only creatures that make similar structures today are bees and wasps.