A period of prehistoric global warming and not the decline of the dinosaurs could be responsible for the rise of mammals, it was claimed today.
Scientists have drawn up a new “tree of life” tracing the history of all 4,500 mammals on Earth which shows they did not spread as a result of the massive asteroid strike that killed off the dinosaurs 65 million years ago.
Most palaeontologists believe the extinction of T Rex and his terrifying cousins permitted our ancestors to flourish and begin the long evolutionary process culminating in the diverse array of species we see today.
But an international team of researchers, which has taken more than a decade to chart modern mammals from existing fossil records and new molecular analyses, show many of the genetic ‘ancestors’ of the mammals existed 85 million years ago – and survived the meteor impact that is thought to have wiped out the dinosaurs.
However, throughout the Cretaceous period 144 to 65 million years ago, when dinosaurs walked the earth, these mammal species were relatively few in number and were prevented from diversifying and evolving in ecosystems dominated by dinosaurs.
The tree of life published in Nature shows after the asteroid strike certain mammals did experience a rapid period of diversification and evolution.
But most of these groups have since either died out completely such as Andrewsarchus – an aggressive wolf-like cow – or declined in diversity such as the group containing sloths and armadillos.
The researchers believe our ‘ancestors’, and those of all other mammals on earth now, began to radiate around the time of a sudden increase in the temperature of the planet – ten million years after the death of the dinosaurs.
Biologist Professor Andy Purvis, of Imperial College London, said: “Our research has shown for the first 10 or 15 million years after the dinosaurs were wiped out present day mammals kept a very low profile while these other types of mammals were running the show.
“It looks like a later bout of ‘global warming’ may have kick-started today’s diversity – not the death of the dinosaurs.
“This discovery rewrites our understanding of how we came to evolve on this planet – and the study as a whole gives a much clearer picture than ever before as to our place in nature.”
Abstract of Nature article.
Hat tip to José Guardia