Sea level changes shaped early life on Earth

Aug. 1 () –

A new chronology of early animal fossils reveals a link between sea levels, changes in marine oxygen and the appearance of the first ancestors of current animals.

The study, published in Science Advancesreveals clues about the forces that drove the evolution of the earliest organisms, from which all major animal groups descended.

A team from the University of Edinburgh studied a collection of rocks and fossils from the so-called Ediacaran-Cambrian interval, a time period from 580-510 million years ago. This period witnessed an explosion of biodiversity according to the fossil record, the causes of which have puzzled scientists since Charles Darwin.

The first animals found from this era were all sea dwellers, at a time when oxygen levels in the air and ocean were much lower than at present.

While early life forms before this time were mostly simple unicellular and multicellular organisms, creatures of the Ediacaran Period began to become more complex, with multiple cells organized into body plans that allowed them to feed, reproduce, and move across the ocean floor.

This era also marked the rise of so-called bilateral animals, which display symmetrical body plans, in common with most living species, including humans.

The new timeline allowed the team to study trends in biodiversity over the period in question in more detail than before.

They combined this knowledge with more chemical clues from the geological record, confirming a link between major changes in global sea levels, intervals in which shallow marine environments They obtained more oxygen and the appearance and diversification of the first animal groups.

This dynamic set the stage for several significant explosions in biological diversity, known as the Avalon, White Sea, and Cambrian assemblages, each of which marked the arrival of new animal groups and the decline of others.

By reconstructing environmental conditions in deeper time, the study reveals new insights into the ancient forces and pressures that shaped early life on our planet.

The team also identified gaps in the fossil record, suggesting that current knowledge about early animals is biased by the groups of sites around the world where fossils have been found and studied.

“Building a timescale of early animal evolution using the rock record is a daunting task, only made possible by international and interdisciplinary research. But an integrated global approach is crucial. It exposes biases in our records, while revealing patterns in fossil appearances, sea level cycles and environmental oxygen,” he says. it’s a statement study author Dr Fred Bowyer, from the School of Geosciences at the University of Edinburgh.

“Knowing what drives biodiversity is a fundamental piece of knowledge in the puzzle of life. I feel very privileged to have built on decades of interdisciplinary global research.” and have contributed to a better understanding of the role played by sea level in early animal evolution”says co-author Mariana Yilales Agelvis.