A study published by scientists at Harvard University has confirmed that during the Industrial Revolution natural selection favored dark butterflies, since they could be better camouflaged in soot.
At the beginning of the 19th century, British scientists observed that black birch moths (Biston betularia ) were increasing markedly. This phenomenon, known as industrial melanism, was explained because, as the trees were covered in soot, the black moths camouflaged themselves more easily and the birds that feed on them did not see them. A few years later the air quality improved and the researchers observed that the number of dark moths decreased again.
Although this is the classic example of evolution by natural selection that is taught in schools and colleges around the world, for years many scientists who follow creationism and intelligent design have suggested that these studies were lax.
The new work, published in the Royal Society’s Biology Letters magazine, consisted of a six-year experiment that, according to its authors, “should dispel all doubts.” The researchers carried out a massive study that consisted of the release of moths of different shades in areas where they usually perch throughout the day such as leaves and tree trunks. Afterwards, each of the animals was observed for two hours to see if any predators ate them or if they finally survived. After analyzing the enormous volume of data, scientists have concluded that dark moths experience 10 percent more predation than light moths . “This means that natural selection is currently favoring light-colored moths,” say the authors of the work.
Study co-author James Mallet says, “This is one of the largest experiments ever done on natural selection. And it confirms that the birch moth is one of the best examples of how natural selection can cause very rapid evolution. “
