Divergent evolution occurs when a population of animals or plants is split into two groups by a geographic barrier (for instance, a body of water or a migration to a new area), causing each group to develop different traits under their respective selective pressures and natural selection. Eventually, the two groups will look or behave so different that they can be considered separate species (a process called speciation), and interbreeding will no longer be possible.

One of the most classic examples of divergent evolution is a case commonly referred to as “Charles Darwin’s finches,” which served as a stepping stone toward his evolution theory.

When Darwin traveled to the Galapagos Islands, he noticed that each island’s birds had different beak shapes and shared a surprising number of other traits. Darwin hypothesized that the entire population of Galapagos finches derived from one common ancestor species, but each population evolved differently depending on the environmental conditions (such as food source) on their particular island. For example, the new species Geospiza magnirostris has an enormous and powerful beak, used for cracking the nuts found on the northern islands.

Darwin’s finches are considered a particular small-scale type of diversification called “adaptive radiation,” in which one population spreads out over several adaptive zones in an ecosystem (in this case, different islands) and diverges.

There are some key differences between the three types of evolution, such as:

• Convergent evolution opposes divergent evolution. Divergent evolution is the functional opposite of convergent evolution. While in divergence, one population evolves separately to form different characteristics. Conversely, convergent evolution is when several different species evolve similar characteristics, often under similar selection pressures. These evolutionary changes can occur through analogous or homologous structures. Analogous structures are features that function similarly but aren’t physically related, such as the wings of a butterfly and the wings of a bat. Homologous structures are features that are physically related but don’t serve the same purpose, such as the arm bones of a human and the flipper bones of a whale. Birds and bats are a good example of convergent evolution. While they are entirely different species, birds and bats have evolved wings for flight to help with feeding and travel. These wings are homologous and analogous structures because they’re both physically and functionally similar.
• Divergent evolution is similar to parallel evolution. In divergent evolution, the two groups of a separated population evolve different traits. In parallel evolution, the two groups of a separated population evolve the same or similar traits. For example, two groups of “flying frogs” have evolved from a common ancestor but were separated across the ocean. In their separate natural habitats, both groups evolved enlarged feet, significant webbing, and skin flaps that allow them to glide from tree to tree.