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Homologies are everywhere
Once you know what a homology is, you can find them anywhere.
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| The leaves of an oak (left) and the leaves of a gingko (right) are homologous — they were both inherited from a common ancestor with leaves. |
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| The wing of a dragonfly (left) and the wing of a butterfly (right) are homologous — they were both inherited from an ancient flying insect. |
Since all life shares a common ancestor, we find homologies
all over the tree of life.
Beyond the obvious
Not all homologies are obvious. If two homologous structures have been adapted for
different roles, they may not look very much alike. For example, the chomping front teeth of a beaver look quite different than the tusks of an elephant.
The beaver uses its teeth for chewing through tree trunks, and the elephant uses its tusks for a number of tasks including digging, peeling bark from trees, and fighting.
But if you examine these two structures closely, you will see that each is a modification of the basic incisor tooth structure. Over time, evolution adapted each of these animals' incisors to perform different functions. They are homologous structures, inherited from a common ancestor with incisor teeth.
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