Toronto: Extinction of dinosaurs 65 million years ago paved the way for mammals to grow a thousand times bigger than they had been.
"Basically, the dinosaurs disappeared and all of a sudden there was nobody else eating the vegetation," says study co-author Jessica Theodor, associate professor in biological sciences at the University of Calgary, Canada.
Theodor says mammals grew from a maximum of about 10 kg when they were sharing the earth with dinosaurs to a maximum of 17 tonnes afterwards, according to a Calgary statement.
"That`s an open food source and mammals start going for it, and it`s more efficient to be an herbivore when you`re big," Theodor adds.
Theodor says the study shows that the ecosystem is able to reset itself relatively quickly.
"You lose dinosaurs 65 million years ago, and within 25 million years the system is reset to a new maximum for the animals that are there in terms of body size."
"That`s actually a pretty short time frame, geologically speaking. That`s really rapid evolution," she says.