Super-fast Evolution Saves Samoa Butterfly from Extinction

Evolve or die. That was the choice faced by the Hypolimnas bolina butterflies on the Samoan islands of Savaii and Upolu. Just six years ago, male butterflies of the species were almost completely gone -- wiped out by a parasite passed on by the females of the species (which themselves were not affected). With male butterflies down to just 1% of the total population, scientists thought the species was a goner. But lo and behold, something happened to change its fate. The butterflies evolved.

Within a few short generations, a genetic mutation that suppresses the killer bacteria has helped the Hypolimnas bolina butterflies bounce back to a point where male and female populations are almost equal. Now, it's unclear if the mutation occurred on its own or if it was introduced by migratory butterflies, but either way, the result is the same. The species has been saved.

Score one for natural selection.