2. Analysis of viral genetic material suggests
viruses DO NOT come from a single common
ancestor.
Three hypotheses to explain the origin of
viruses:
3. 1. Devolution (Regression) Hypothesis
•Viral ancestors were cellular organisms similar
to bacteria.
•Evolved into obligate parasites
•Parasites lost cellular components as it was
more efficient to reproduce without.
•
4. 2. Escapist (Progressive) Hypothesis
•Genetic material from a free living (non-parasitic)
cell “escaped” wrapped in protein coat
•Explains viral-host specificity (viruses are able to
attack and take over host because they came from
them)