Early animal evolution got off to a hot start before Ice Age slowdown

"This early phase of evolutionary divergence appears to have preceded the extreme climate changes that led to Snowball Earth," said paleontologist Martin Dohrmann.
By Brooks Hays   |   June 15, 2017 at 4:50 PM
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June 15 (UPI) -- Early animal evolution occurred more rapidly than previously thought, new research suggests.

Fossil records show all animal phyla had materialized by the beginning of the Cambrian Period, roughly 540 million years ago. But the scarcity of early animal fossils make it difficult to establish a more accurate timeline for early animal evolution.

To map the roots of the animal kingdom's family tree, researchers rely on what's called a molecular clock. The molecular clock analyzes the accumulation of genetic mutations to measure how long ago different lineages diverged.

"Our study is based on a combination of genetic data from contemporary animals and information derived from well dated fossils, which we analyzed with the help of complex computer algorithms," Martin Dohrmann, a paleontologist at the Ludwig Maximilian University of Munich, said in a news release.

Scientists analyzed genetic mutations in 128 proteins from 55 species, representing animal groups. Researchers focused on lineages that diverged extremely early.

The survey's findings -- detailed in the journal Scientific Reports -- confirmed that the earliest animals emerged between 1000 and 540 million years ago, during the Neoproterozoic Era. More surprisingly, the analysis suggests all bilateral animal species, encompassing most animal phyla, emerged during a brief geologic window -- a time-span of just 50 million years.

"In addition, this early phase of evolutionary divergence appears to have preceded the extreme climate changes that led to Snowball Earth, a period marked by severe long-term global glaciation that lasted from about 720 to 635 million years ago," Dohrmann said.

The ice age put the breaks on this early acceleration of evolution.

Their work, of course, isn't done. Researchers say they need to paint a more accurate picture of ecological conditions during the Neoproterozoic Era in order to truly understand early animal evolution.

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