First Animals Evolved in Lakes, Not Oceans, Study Hints

Many scientists have argued that these first, complex creatures arose in the oceans.

"It just seems like a fairly reasonable thing to assume, given the chemical and environmental stability of the oceans," said Martin Kennedy of the University of California, Riverside.

But a new study of one of the oldest known fossil beds has revealed abundant amounts of a mineral called smectite, which forms in salty, alkaline lakes—not seawater.

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