The discovery of a trove of insects preserved for millions of years in amber raises new questions about how long India was isolated before it joined the Asian continent, researchers said in a study published this week.
The insects – bees, termites, spiders, and flies – had been entombed in the vast Cambay deposit in western India for some 50 million years, the researchers describing this amber as the oldest evidence of tropical forests in Asia.
“The amber shows, similar to an old photo, what life looked like in India just before the collision with the Asian continent,” says Jes Rust, professor of Invertebrate Palaeontology at the Universitaet Bonn in Germany.
Not so unique after all
Scientists had long assumed that India was for a time an isolated island-continent in the Early Eocene, or 52–50 million years ago, and consequently expected that the insects found in the amber would differ significantly from those elsewhere in Asia.
But in a study published in Proceedings of the National Academy of Sciences researchers say that the insects were not as unique as would be expected had India been sequestered for as long as they originally believed.
“We know India was isolated, but when and for precisely how long is unclear,” says David Grimaldi, curator in the Division of Invertebrate Zoology at the American Museum of Natural History. “The biological evidence in the amber deposit shows that there was some biotic connection,” he wrote.
This ant was found in the Cambay amber deposit of western India
Discovering unexpected evolutionary ties
India separated from present-day Africa and after about 50 million years collided with Asia, creating the Himalayas.
But rather than finding evolutionary ties to Africa and Madagascar – land masses geologists say India was most recently linked to – the researchers found relatives in Northern Europe, Asia, Australia, and the Americas.
“What we found indicates that India was not completely isolated, even though the Cambay deposit dates from a time that precedes the slamming of India into Asia,” says Michael Engel, a professor in the Department of Ecology and Evolutionary Biology and curator of entomology at the University of Kansas. “There might have been some linkages.”
“The insects trapped in the fossil resin cast a new light on the history of the sub-continent.”