MADRID Dec. 19 () –
Virginia Tech geobiologist Shuhai Xiao and his collaborators publish in Science a high-resolution analysis of the global diversity of Proterozoic life based on a global compilation of fossil data.
Xiao and his team specifically analyzed records from ancient marine eukaryotes, organisms whose cells contain a nucleus. The first eukaryotes later evolved into the multicellular organisms credited with ushering in a new era for life on Earth, including animals, plants and fungi.
“This is the most complete and up-to-date analysis of this period to date,” says Xiao, who recently joined the National Academy of Sciences. “More importantly, we used a graphical correlation program that allowed us to achieve higher temporal resolution.” Thus, the choreography of species offers critical perspectives on the parallel paths of the evolution of life and the Earth.
The first eukaryotes emerged no more than 1.8 billion years ago and gradually evolved until they reached a stable level of diversity between about 1,450 and 720 million years ago, a period aptly known as the “boring billion,” when turnover rates of species were remarkably low. The eukaryotic species of the “boring billion” may have evolved more slowly and lasted longer than those that came after.
Then came the cataclysm: Snowball Earth, a spiral of free-falling temperatures, which sealed the planet in ice at least twice between 720 and 635 million years ago. When the ice finally melted, evolutionary activity resumed and things were no longer so boring. “The ice ages were an important factor that reset the evolutionary path in terms of diversity and dynamics,” Xiao recalls. “We see a rapid turnover of eukaryotic species immediately after the ice age. That’s an important finding.”
Future scientists can use the quantified pattern to better understand the complex interaction of life on Earth and the Earth itself.
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