The molecular mechanics behind a classic example of evolution that dates back to Darwin’s time may soon be revealed.
As soot from coal-fired factories blackened trees and buildings in 19th century England, naturalists noticed that peppered moths were also trading in their light-colored wings sprinkled with black specks for a sleek, all-black stealth-bomber look known as the carbonaria form. Within a few decades of their first appearance near Manchester, the black moths dominated, making up 90 percent or more of the peppered moth population in local urban areas.
Biology textbooks often cite peppered moths as a classic example of adaptation to changing environmental conditions. The trouble is, no one really knew which molecular changes led the moths to switch wing color. It was an open debate whether the change, which presumably allowed moths to blend better into the increasingly grimy background and avoid bird predators, was due to one mutation or many, and if the adaptation occurred once or several times.