Understanding Evolution: your one-stop source for information on evolution
Resource library Teaching materials Evolution 101
print print

Homologies are everywhere

Once you know what a homology is, you can find them anywhere.

oak leaves gingko leaves
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.

dragonfly butterfly
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.

beaver 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.


previous
Inheriting homologies

  next
Not all similarity is homology


Oak photo © Br. Alfred Brousseau, Saint Mary's College; Gingko photo provided by Mike Clayton and the University of Wisconsin, Madison Virtual Foliage page; Dragonfly photo provided by Gerald and Buff Corsi © California Academy of Sciences; Butterfly photo provided by T. W. Davies © California Academy of Sciences; Beaver photo © 2000 Don Getty; Elephant photo provided by Gerald and Buff Corsi © California Academy of Sciences

previous | next  >


More details
Homologies can be identified in many places; it's not just anatomy.