The Industrial Revolution set off many changes that resound even today. Technology improved, manufacturing blossomed and jobs were abundant. Unfortunately, all of these advances occurred at the expense of the environment.
In England, smokestacks bellowed out huge clouds of soot from burning coal. Skies darkened, and the air became polluted. Among all of these changes came a change in Biston betularia, the peppered moth that inhabits the United Kingdom. As soot blackened their environment, the normally light moths became jet black.
For years, people accepted the evolution of the light-colored typica moth to the darker carbonaria moth as evidence of Darwin’s theory of natural selection, but only lately have scientists started to understand the molecular mechanism that gave rise to the change in wing color. Researchers at the University of Liverpool have located the locus in the moth genome that produces wing color.
This locus is similar in both moths and butterflies and is significant because it is the site of the many mutations and recombinations that result in wing coloring and patterning, which are essential to the organisms’ chances of survival.
For example, certain butterflies may mimic the bright colors of toxic species to avoid predation. In the case of these moths, the light colors and black speckles allowed the moth to blend in perfectly with trees while the jet black moth had a higher chance of being eaten. However, as the environment became more and more polluted, the black moths were able to better camouflage themselves in their surroundings, making the typica moth more likely to become a quick snack.
Consequently, Britons saw an increase in the population of the carbonaria moths while the lighter types became much harder to find. This became one of the signature species that correlated to Darwin’s idea of “survival of the fittest.”
However, it was in how the black patterning developed that raised questions about evolution. While the general location of the locus is known, researchers have not yet identified exactly which genes and which regulatory elements are involved in producing the wing color.
They do know where in the genome they should be looking, considering the fact that every carbonaria moth collected from the 80 different sites had the same genetic markers in the area of interest. They also believe that instead of there being several mutations involved in forming the black moth, there really is only one that shortly predated the Industrial Revolution, but became more prominent as the skies of England became darker.
Coincidentally, the British Isles worked on cleaning up the air. Now that it is considerably more breathable and significantly clearer, there has been an increase of the typica form of moth. This again emphasizes the role of natural selection in this process. While the exact molecular mechanism has not yet been elucidated, scientists know where to start.
