Prehistoric animals may have started their drive towards explosive diversity when the Earth was a giant snowball about 540 million years ago, according to a new study.
Scientists, who analysed the fossil records and genomes of existing organisms related to species of the Cambrian period (the zoological era that spanned from 540 to 480 million years ago), found that expansion in the diversity of life forms began early in that period.
During this apparently sudden outburst all the major groups of animals seemed to materialise rapidly.
The results suggested that many of Earth's early organisms developed the genetic programmes for their body plans during the Cryogenian period, which lasted from 850 to 635 million years ago, with the last common ancestor of all living animals originating nearly 800 million years ago.
During the Cryogenian period, studies suggest the planet may have been a "Snowball Earth", completely coated in ice for stints of millions of years. The deep freeze could have spurred the evolution by pumping a surge of nutrients into the oceans, the researchers said.