Ancient Records Are Prompting To Rethink Of Animal Evolution Timeline

After gaining fresh insights into how life on Earth diversified millions of years ago, scientists are rethinking a huge milestone in animal evolution. According to researchers, evolutionary activity bursts which raised the number and variety of animals started earlier, occurred over a longer timeframe and were more frequent than previously thought.

Their findings challenge a long-held theory which suggests the huge expansion in the types of animals on the planet more than 500 million years ago was triggered by a single, rapid surge of evolution which is known as the Cambrian Explosion.

Geoscientists from the University of Edinburgh re-assessed the timeline of early animal evolution by doing analysis on records of fossil discoveries and environmental change. The Cambrian Explosion until now, which has taken place between 540 and 520 million years ago, was thought to have given an increase to almost all the early ancestors of present-day animals.

However, according to some scientists, it was probably just one in a series of similar events, the first of which took place during the late Ediacaran Period at least 571 million years ago. These bursts of evolutionary activity could have coincided with dramatic fluctuations in the oxygen levels and necessary nutrients in the oceans, the team says.

Nature Ecology & Evolution published the review in the journal. It was supported by the Natural Environment Research Council. The research also involved the Universities of Bristol, Tokyo Institute of Technology, Cambridge and Helsinki, Japan, and the Memorial University of Newfoundland in Canada.

Professor Rachel Wood, of the University of Edinburgh's School of GeoSciences, who led the study, said that integrating data from the fossil record with that of environmental changes which affected the whole planet is reflecting the patterns and drivers of the rise of complex life on Earth. They used to think early animals emerged rapidly following a single evolutionary event, but our findings suggest it actually happened in stages.

By: Preeti Narula

Content: https://www.sciencedaily.com/releases/2019/03/190311125146.htm