Precambrian cratons -- some of Earth's oldest rocks -- were uninhabitable for microbes for much of their existence, with the longest period of habitability not much beyond a billion years, and many only for the past 50 million to 300 million years, according to a paper correlating Earth's deep biosphere with geologic history.
PTELook at the text below. In 35 seconds, you must read this text aloud as naturally and clearly as possible. You have 35 seconds to read aloud.
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Beginning in 35 seconds.