There are three leading hypotheses to explain the evolutionary origin of viruses, known to scientists in the field as viruses-first, escape, and reduction. Viruses-first is the idea that viruses came into existence before cells, somehow assembling themselves directly from that primordial cookery of self-replicating molecules. The escape hypothesis posits that genes or stretches of genomes leaked out of cells, became encased within protein capsids, and went rogue, finding a new niche as parasites. The reduction hypothesis suggests that viruses originated when some cells downsized under
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