What is a homologous structure?

A homologous structure is an anatomical feature that is similar in different species because it was inherited from a common ancestor. These structures may have different functions in each species, but they share a common underlying structure. Homologous structures are evidence of evolution and are used to infer relationships between different species.

For example, the pentadactyl limb structure found in mammals, birds, reptiles, and amphibians is a homologous structure. Despite the limbs serving different functions in each species, they all share a common bone structure with five digits, suggesting a shared evolutionary history.

Homologous structures can be used to map out the evolutionary relationships between different species through comparative anatomy. By comparing the similarities and differences in homologous structures between organisms, scientists can better understand how different species are related and how they have evolved over time.