The species Homo sapiens evolved some 300,000 years ago and has come to dominate Earth unlike any species that came before. But how long can humans last?

Eventually humans will go extinct. At the most wildly optimistic estimate, our species will last perhaps another billion years but end when the expanding envelope of the sun swells outward and heats the planet to a Venus-like state.

But a billion years is a long time. One billion years ago life on Earth consisted of microbes. Multicellular life didn’t make its debut until about 600 million years ago, when sponges proliferated. What life will look like in another billion years is anyone’s guess, though one modeling study published in 2021 in Nature Geoscience suggests that Earth’s atmosphere will contain very little oxygen by then, making it likely that anaerobic microbes, rather than humans, will be the last living Earthlings.

If surviving to see the sun fry Earth is a long shot, when is humanity likely to meet its doom? Paleontologically, mammalian species usually persist for about a million years, says Henry Gee, a paleontologist and senior editor at the journal Nature, who is working on a book on the extinction of humans. That would put the human species in its youth. But Gee doesn’t think these rules necessarily apply for H. sapiens.

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