What is Artificial Selection?
When nature exerts selection pressure on a species (or in other words, creates a situation that gives organisms with certain traits a reproductive advantage), we call it natural selection. But what about when humans are the ones that exert the selection pressure? We call this “artificial selection”.
You have almost certainly spent a lot of time around, or even lived with, organisms that are the result of artificial selection. One of these organisms is sometimes known as “man’s best friend”.
Domestic dogs originally arose from gray wolves, and are still so closely related that they can interbreed and produce fertile offspring. However, if you were to show a gray wolf and a pug to aliens that had never heard of dogs before, they probably wouldn’t think they were related to each other.
Domestic dogs range from small enough to fit in a purse to several hundred pounds; they come in all kinds of coat textures, colors, and lengths. Some have unnaturally long, elegant noses, and other have snouts that are pushed in to the point that it obstructs their breathing. Yet they are all the same species.
This huge variation in traits is the result of hundreds of years of artificial selection. The ancestors of modern dogs probably started to hang around human villages to take advantage of their food scraps. Over time, the dog-ancestors that were the friendliest and least afraid of humans were “adopted” into human society; gaining extra food and protection from humans gave them a survival advantage over their more wild relatives.
Eventually humans began intentionally breeding dogs to have certain traits. For example, they might breed the dogs with the curliest fur together for multiple generations until their produced offspring that always had curly fur. Over time these breeding projects turned into the breeds of dog we know today.
Humankind has also domesticated many other animal and plant species. Nearly every crop you eat is the result of natural selection; we bred plants to produce larger and more flavorful vegetables and fruits to provide us more food.
Sometimes artificial selection can even happen by accident. For example, people started baiting cockroaches with sugary-flavored poison to eradicate them from their houses. Over time this selection strategy began to heavily favor cockroaches that weren’t as attracted to the taste of sugar. Now there are whole populations of cockroaches that are resistant to certain types of roach bait.
Unlike natural selection, which has been acting on species for hundreds of thousands of years, the effects of artificial selection can be undone fairly quickly. Populations of feral dogs or horses lose their breed-distinguishing traits and begin to look like generic, primitive dogs or horses within a couple of generations.
Free-Photos (photographer). (2015). Pug Dog Pet [photography]. Retrieved from https://pixabay.com/vectors/evolution-walking-charles-darwin-297234/