Biology / Unit 9 Bio 1915 short lesson, about 20 seconds
Three Hypotheses for Viral Origin
Captions available
The idea
Three hypotheses compete for how viruses originated— regressive, progressive, and virus-first— and the field has not settled which, if any, is correct.
In practice
The regressive hypothesis proposes viruses devolved from free-living cells; the progressive hypothesis proposes they escaped from mobile genetic elements.
Where people slip
The regressive hypothesis does not claim viruses are ancestors of cells— it claims the reverse: viruses descend from cells.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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