Artificial selection provides a model that helps us understand natural selection.
People have been artificially selecting domesticated plants and
animals for thousands of years. These activities have amounted to
large, long-term, practical experiments that clearly demonstrate
that species can change dramatically through selective breeding.
Broccoli and brussels sprouts bear little superficial resemblance
to their wild mustard relatives (right).
If domesticated dogs were discovered today they would be classified
as hundreds of different species and considered quite distinct from
wolves. Although it is probable that various breeds of dogs were
independently domesticated from distinct wild dog lineages, there
are no wolf relatives anywhere in the world that look much like
dachshunds or collies (below).
These observations demonstrate that selection has profound effects on
populations and has the ability to modify 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 envision natural conditions acting
selectively on populations and causing natural changes.