Filling in the evolutionary gaps:

The rapidity of speciation has perplexed generations of scientists, among them Darwin himself, who devoted a whole chapter to the Cambrian in On the Origin of Species and considered it a potential objection to his theory of evolution. Darwin eventually concluded that the Cambrian's evolutionary divergences started earlier, but left no trace in the fossil record. Stephen Jay Gould called it "the most remarkable and puzzling event in the history of life."

What's at the heart, then, of this most remarkable and puzzling event? Poop, says [geoscientist Graham] Logan.

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