If the Universe Is Teeming with Aliens ... WHERE IS EVERYBODY?: Seventy-Five Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life

by Stephen Webb

Unfortunately, biologists can push this approach only so far. One commonly drawn picture is that LUCA was already a sophisticated organism, which had evolved considerably from the time when life first arose, before it branched into the domains of archaea and bacteria.

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