Eukaryotic red and green algae populated the tropical ocean 1400 million years ago

Both molecular clocks and the fossil record indicate that eukaryotic algae evolved by the late Paleoproterozoic Era (2500 to 1600 million years ago, Ma). However, the biomarker record of steranes does not reveal their presence until the early Tonian Period (1000 to 720 Ma), suggesting that eukaryotic algae were insignificant ecosystem members for some one billion years after they evolved. Here, we conducted high-temperature pyrolysis and fixed-bed catalytic hydropyrolysis of kerogen from the ca. 1400 Ma Xiamaling Formation, liberating a host of lipid molecules, including C-27 to C-29 steranes. With sterane to hopane ratios ranging up to 0.17, our results indicate the presence of significant populations of both red and green algae at 1400 Ma, some 600 million years earlier than previously recognized.

Automated summary

Research on kerogen from the ca. 1400 Ma Xiamaling Formation suggests the presence of significant populations of both red and green algae, some 600 million years earlier than previously recognized.