Three Hypotheses for Viral Origin
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Three hypotheses compete for how viruses originated— regressive, progressive, and virus-first— and the field has not settled which, if any, is correct.
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The regressive hypothesis proposes viruses devolved from free-living cells; the progressive hypothesis proposes they escaped from mobile genetic elements.
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The regressive hypothesis does not claim viruses are ancestors of cells— it claims the reverse: viruses descend from cells.