For example, the forelimbs of humans, bats, and whales are all homologous structures because they are derived from the same embryonic limb buds and have the same basic skeletal structure, even though they may differ in size, shape, and function.
Here are some additional examples of primary homology:
* The wings of birds and the arms of humans and bats
* The legs of humans and the hind legs of kangaroos
* The antennae of insects and the feelers of crustaceans
* The roots of plants and the rhizomes of ferns
Primary homology is important for understanding the evolution of organisms because it allows scientists to trace the relationships between different species and to identify common ancestors.