Here's why:

* Homology refers to the similarity of structures in different species due to shared ancestry. This means that the structures have a common origin, even if they have different functions in the present day.

* Comparative anatomy studies the similarities and differences in the anatomy of different organisms, often focusing on homologous structures.

Examples of Homology:

* The wings of a bat, the flippers of a whale, and the arms of a human are all homologous structures. They have the same basic bone structure, even though they perform different functions.

* The presence of gill slits in the embryos of all vertebrates, including humans, is another example of homology. This suggests that all vertebrates share a common ancestor that had gills.

Homology is a powerful tool for understanding evolutionary relationships. By comparing the anatomical structures of different organisms, we can infer their evolutionary history and trace their descent from a common ancestor.