Scientists untangle interactions between the Earth’s early life forms and the environment over 500 million years

The atmosphere, oceans, and life on Earth have interacted over the past 500 million years to improve the conditions for early organisms to thrive. Now, an interdisciplinary team of scientists has written a Perspective on this coevolutionary history. Published in National Science Review.

“One of our jobs is to carbon dioxide “We looked at changes in Earth and oxygen in the atmosphere and oceans over the past 500 million years,” says Zunli Lu, a professor of geochemistry at Syracuse University and lead author of the paper. “We looked at how these physical changes influenced the evolution of life in the oceans. But it goes both ways: the evolution of life also influenced the chemical environment. Understanding how to build a habitable Earth over long timescales is not an easy task.”

A team of researchers from Syracuse, Oxford and Stanford universities investigated the complex feedback loops between ancient life forms, including plants and animals, Chemical Environment The current Phanerozoic era began about 540 million years ago.

At the beginning of the Phanerozoic Era, atmospheric carbon dioxide concentrations were high; Oxygen levels Such conditions would make it difficult for many modern organisms to thrive. But seaweed has changed that. It absorbs carbon dioxide from the atmosphere and uses it to organic matter Oxygen was produced through photosynthesis.

Animals’ ability to survive in marine environments depended on oxygen levels. Lu is using geochemical proxies and model simulations to study where and when ocean oxygen levels rose or fell during the Phanerozoic Era. Co-author Jonathan Payne, professor of Earth and Planetary Sciences at Stanford University, compares the estimated metabolic requirements of ancient animals with where they survived or disappeared during the Phanerozoic Era. Fossil record.

As Photosynthetic algae Removing carbon from the atmosphere Sedimentary rocks When carbon dioxide was reduced and oxygen levels increased, the algae’s enzymes became less efficient at fixing carbon, so the algae had to create more complex ways of photosynthesis to reduce carbon dioxide and increase oxygen levels, and they achieved this by creating internal compartments for photosynthesis with controlled chemical reactions.

“In the case of algae, the O₂/CO₂ It is believed to be the key to improved driving. Photosynthetic efficiency“What’s really intriguing is that these improvements in photosynthetic efficiency could have expanded the chemical habitability range for many forms of life,” said co-author Rosalind Rickaby, professor of geology at the University of Oxford.

Ancient photosynthetic organisms had to adapt to changes in the physical environment they created, Lu points out: “The first half of Phanerozoic history is about improving habitability for life, and the second half is about adaptation.”

If scientists want to better understand the interactions between life and the physical environment, and the drivers and limits of habitability, the authors say: Ocean Biomarkers of oxygen, photosynthesis, and metabolic tolerance of animals represented in the fossil record will be important future research directions.