Mitochondria descend from free-living bacteria that came to live inside an ancestral host cell. How the bacterium got in, and what the host was, are still debated.
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The claim is a loose way of saying many human genes have distant counterparts in bananas. Estimates run from about 25% to 60% depending on method, and shared DNA is far lower, around 1%.
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Goosebumps are an involuntary reflex in which tiny muscles pull hairs upright. It is a leftover from furrier ancestors, triggered by cold and by strong emotion.
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Sexual selection is evolution driven by success in winning mates rather than surviving. Darwin found the peacock's costly tail hard to explain by natural selection alone.
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