Paleontologists led by David Gold are uncovering the evolution of early life through chemical signatures in ancient rocks and genetic studies. They found that changes in sterol lipids in the rocks corresponded with significant changes in animal diets and increases in algae, shedding light on life more than a billion years ago.

Paleontologists are gaining glimpses of life over the past billion years based on chemical signatures in ancient rocks and the genetics of living animals. Research results announced on December 1st nature communications Combining geology and genetics, it shows how changes in the early Earth prompted changes in the way animals ate.

Molecular paleontology: bridging geology and biology

David Gold, an associate professor in the Department of Earth and Planetary Sciences at the University of California, Davis, works in the new field of molecular paleontology, which uses tools from both geology and biology to study the evolution of life. . A new technique allows researchers to recover chemical signatures of life from ancient rocks where animal fossils are rare.

Lipids in particular can survive in rocks for hundreds of millions of years. Trace amounts of sterol lipids derived from cell membranes have been found in rocks dating back 1.6 billion years. Most animals now use cholesterol, a 27-carbon (C27) sterol, in their cell membranes. In contrast, fungi typically use C28 sterols, and plants and green algae produce C29 sterols. C28 and C29 sterols are also known as phytosterols.

Tracking the evolution of life through chemical markers

C27 sterols have been found in rocks that are 850 million years old, and traces of C28 and C29 appear about 200 million years later. This is thought to reflect the increased diversity of life at this time and the evolution of the first fungi and green algae.

Without actual fossils, it’s difficult to say much about the animals and plants these sterols come from. However, genetic analysis by Gold and colleagues has shed some light.

Don’t make it, eat it

Most animals cannot make phytosterols themselves, but they can obtain them by eating plants and fungi. Recently, annelids (a group that includes segmented worms and common earthworms) smt, required to make long-chain sterols.by seeing smt Gold and colleagues used the genes of different animals to create family trees. smt first within annelids and then across animals in general.

They discovered that this gene originated long before the evolution of the first animals and then underwent rapid changes around the same time that phytosterols appeared in the rock record. After that, most animal lineages smt gene.

“Our interpretation is that these phytosterol molecular fossils document an algae outbreak in the ancient oceans, when animals had easy access to phytosterols from this increasingly abundant food source. “We think they may have abandoned production of phytosterols,” Gold said. “If we are right, the history smt Genes record changes in animals’ feeding strategies early in evolution. ”

Reference: “A common origin of sterol biosynthesis suggests changes in feeding strategies in Neoproterozoic animals” T. Brunoir, C. Mulligan, A. Sistiaga, KM Vuu, PM Shih, SS O’Reilly, RE Summons, DA Gold, November 31, 2023; nature communications.
DOI: 10.1038/s41467-023-43545-z

The co-authors of this paper are: hers Tessa Brunoir and Chris Mulligan of the University of California, Davis; Ainara Sistiaga, University of Copenhagen. KM Vuu and Patrick Shih, Joint BioEnergy Institute, Lawrence Berkeley National Laboratory; Shane O’Reilly, Atlantic Institute of Technology, Sligo, Ireland. Roger Sammons, Massachusetts Institute of Technology. This research was supported in part by a grant from the National Science Foundation.