Ancient Genes for Symbiosis Hint at Mitochondria’s Origins

Once, long ago, the only players in the grand drama of life, predation and death were invisibly small and simple cells. Archaea and bacteria jigged and whirled through seas and ponds, assembled themselves into fortresses a few microns wide, and devoured films of organic matter. Then some of them began to change, and eventually the first eukaryote — the first organism to keep its genes locked away…

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