Discomedusae #8 by Ernst Haeckel (1899)

This week, SFI hosts a three-day working group to explore the effect of increasing oxygen on the early evolution of animals.

“For decades, there have been outstanding questions about the issue of oxygen and early animal evolution,” says organizer Doug Erwin, SFI External Professor and Senior Scientist at the Smithsonian’s National Museum of Natural History.

The origin of animals at least 600 million years ago was a critical event in Earth’s history. Their millions of descendants include jellies, trilobites, worms of every description, octopuses, and vertebrates like us.

What triggered the appearance and diversification of the first animals is a subject of intense interest. Erwin and his co-organizer of the upcoming meeting — Noah Planavsky, an assistant professor of geology and geophysics at Yale University — note that some geologists and paleontologists have “rather blithely invoked oxygen levels” as the likely trigger.

“It’s pretty clear that there was an increase in oxygen in shallow oceans between about 800 million years ago and 500 million years ago,” says Erwin. “But the actual pattern of increase, we don’t know.”

Researchers also don’t know exactly how such changes might have impacted evolution, says Erwin. A sharp jump in oxygen levels might have triggered the evolution of large animals capable of preying on smaller animals. For other aspects of evolution, oxygen levels might have been irrelevant.

The small working group includes disparate points of view and expertise and Erwin expects passionate but good-natured discussion at the April meeting. “Everybody in the group wants to know what the answers are. If we have some consensus on some of these issues, it will make it more obvious how to move forward.”

At the end, the group will summarize their conclusions, outstanding questions, and new directions for research in a paper for the journal Geobiology.

Read more about the working group.