What term describes structures that share a common evolutionary origin?

Structures that share a common evolutionary origin are called homologous structures. They may perform different functions in different organisms because descendants modified an inherited structure after diverging from a common ancestor.

The forelimbs of humans, bats, whales, and horses are a classic example. Each contains corresponding bones—including the humerus, radius, ulna, wrist bones, and digits—yet those limbs are adapted for grasping, flying, swimming, or running. Their underlying arrangement reflects shared ancestry, while natural selection shaped each version for its environment.

The biological concept of homology was formalized in the nineteenth century, especially through the work of anatomist Richard Owen. Charles Darwin later explained homologous similarities as evidence that species descended from common ancestors and diverged over time.

Homologous structures are often confused with analogous structures. Analogous structures perform similar functions but evolved independently, such as the wings of birds and insects. Vestigial structures are different again: they are reduced remnants inherited from ancestors, such as the human tailbone. A structure can therefore be homologous in origin even when its modern purpose looks completely different.