The history of life on Earth is marked by cyclic periods of explosive evolution. But, until recently, the mechanisms behind these bursts of biodiversity were largely unknown.
Now, researchers have found that these biological blooms may be driven by the movement of the Earth’s tectonic plates over cycles of 36 million years.
By analyzing the fossil record and geological data, the global team was able to decipher clear links between changes in the Earth’s biological makeup and cyclic tectonic movement. The results of this analysis were published in the journal Proceedings of the National Academy of Sciences on June 10.
“In terms of tectonics, the 36-million-year cycle marks alterations between faster and slower seafloor spreading, leading to cyclical depth changes in ocean basins and in the tectonic transfer of water into the deep Earth,” co-author Dietmar Müller, from the School of Geosciences at the University of Sydney, said in a statement.
“These in turn have led to fluctuations in the flooding and drying up of continents, with periods of extensive shallow seas fostering biodiversity.”
In other words, these geological cycles drive changes in sea level that in turn disrupt the composition of marine ecosystems. The environments that result from these changes offer opportunities for new species to arise and exploit these new habitats. Other species, meanwhile, may go extinct as their old habitats have been lost.
“The cycles are 36 million years long because of regular patterns in how tectonic plates are recycled into the convecting mantle, the mobile part of the deep Earth, similar to hot, thick soup in a pot, that moves slowly,” Müller said.
To demonstrate how sea level change can dramatically affect ecological landscapes, Müller pointed toward’s Australia’s Winton Formation, a region of sedimentary rock in central-western Queensland that represents one of the richest sources of dinosaur fossils anywhere in Australia. It is also from a time when most of the continent was underwater, around 100 million years ago.
“The Cretaceous Winton Formation stands as a testament to the profound impact of these sea-level changes, capturing a snapshot of a time when Australia’s landscape was transformed and fascinating creatures roamed the land,” Müller said.
This study provides new insights into the mechanisms that drive species evolution, showing how ecology and geology exist hand in hand, and goes some way to explain evolutionary patterns that stand out in the fossil record.