One of the fastest evolutionary changes ever observed has been witnessed by scientists studying butterflies in the South Pacific, the BBC reports. Blue Moon butterflies managed to fight off a deadly parasitic bacteria by developing suppressor genes to fight the bacteria in just six years. Hard-hit males rebounded from 1% of the population to 40% in that time.
"We usually think of natural selection as acting over hundreds of thousands of years, but in this study [it] happened in the blink of the eye," said a scientist. Investigators are uncertain if the gene developed as a mutation or was introduced by migratory butterflies. The findings reveal how such biological "arms races" can drive evolution. (Read more nature stories.)