|By Andrew McDonald | 3 years ago|
Researchers who have analyzed the chemical fingerprints of life in ancient rocks find that during the 15 million years between two “snowball Earths” — when glaciation periods covered the planet in ice from the poles to the equator 700 million and 659 million years ago — life made the transition from microbes to multicellular forms.
Jochen J. Brooks, a geologist from Australia National University in Canberra, and his colleagues analyzed traces left by cell membranes in rocks up to one billion years old, a report by Ars Technica said. By looking at the chemical changes in the membranes, the researchers saw a marked increase of new, larger forms of sea plankton algae in the warming waters after the first total glaciation, called the Sturtian snowball.
The team suggests that life got a kick-start from the huge amounts of nutrients and carbon dumped into the oceans by melting glaciers.
“Such massive burial of reduced carbon must have been balanced by a net release of oxygen into the atmosphere, initiating the protracted oxygenation of Neoproterozoic deep oceans,” the scientists write.
The increased oxygen in the oceans likely led to an increase in phosphorous, which is one of the key building blocks of DNA. As more complex life forms life algae diversified, others evolved to prey on them. Then, when the climate stabilized about 550 million years ago, the geological record shows the emergence of animals with internal organs, heads, and tails.
The study is published in the journal Nature.