Artificial selection is an evolutionary process in which humans consciously select for or against particular features in organisms – for example, by choosing which individuals to save seeds from or breed from one generation to the next. People have been artificially selecting plants and animals for thousands of years. These activities have amounted to large, long-term, practical experiments that clearly demonstrate that species can evolve dramatically through selective breeding.

Artificial selection on wild mustard
For example, cauliflower, broccoli, cabbage, kale, and kohlrabi bear little superficial resemblance to their wild mustard relatives. And yet, through many generations of artificial selection, these five distinct crops were intentionally evolved from a wild, weedy ancestor.

Artificial selection on domestic dogs
Dog domestication provides another dramatic example of the power of artificial selection. The ancestors of pet dogs were probably domesticated from multiple distinct wolf lineages just 20,000 to 40,000 years ago. Since then, human selection has produced an enormous variety of breeds (many of which were artificially selected for in just the last 200 years).  For example, dachshunds were selected to flush out and hunt small animals, while German Shepherds were selected for herding sheep. Modern domestic dog breeds come in such a variety of shapes and sizes that we might well have classified them into dozens of different species if we did not know their history.

These observations demonstrate that selection can have profound effects on populations and has the ability to modify the forms and behaviors of living things to the point that they look and act very unlike their ancestors. Artificial selection provides a model that helps us understand natural selection. It is a small step to go from humans selecting desirable traits in plants and animals to envisioning natural conditions acting selectively on populations and causing natural changes, especially over geological timescales.