Mass Extinctions Happen Every 27 Million Years

Scientists have new evidence that Earth’s many periodic mass extinctions follow a cycle of about 27 million years, connecting the five major mass extinctions with more minor ones occurring throughout Earth’s life-fostering timespan. The artificial intelligence analysis could also shift how evolutionary scientists think about the aftermath of mass extinctions.

One of the hallmarks of evolutionary science is a series of explanations and hypotheses that are later proven wrong. This is a normal part of almost every ongoing scientific inquiry, and evolution is an especially complex idea for humans to try to make sense of: wrapped up in what we believe our place is on the planet, conflicting religious messaging, and pure existential questions that cut to our hearts.

Coincidentally—or not—we’ve developed an idea of evolution that says mass extinctions are what allow subsequent species to evolve and flourish. In the most literal sense, it’s true that species that exist now were preceded by many that died out. But do these mass extinction events cause and enable that flourishing?

The new research, which appears in Nature, says no—or at least not only that:

“Scientists have long believed that mass extinctions create productive periods of species evolution, or ‘radiations,’ a model called ‘creative destruction.’ A new study led by scientists affiliated with the Earth-Life Science Institute (ELSI) at Tokyo Institute of Technology used machine learning to examine the co-occurrence of fossil species and found that radiations and extinctions are rarely connected, and thus mass extinctions likely rarely cause radiations of a comparable scale.”

To study these events, the scientists fed more than a million data points about 170,000-plus species into a machine learning algorithm that processed all of it into one giant statistical timeline. From that information, the algorithm concluded that while the “big five” mass extinctions are part of the top 5 percent of all time population change events, so are “seven additional mass extinctions, two combined mass extinction–radiation events and 15 mass radiations.”

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