Concept explainers
What Good Are Wisdom Teeth and Ostrich Wings?
Ostrich wings are vestigial because they are too rudimentary to perform the function for which they evolved in the species’ flying ancestor. Nonetheless, the ostrich uses its wings for other purposes. For example, an ostrich may extend its wings to the side while running, to help maintain balance, and it may spread its wings as part of a threat display. These uses show that evolution by natural selection can sometimes repurpose vestigial structures that have lost the function for which they originally evolved. But whether a vestigial structure remains useless or acquires a new function, it is homologous to the version that retains its original function in other organisms and provides evidence of common ancestry. But are all similarities between different organisms the result of shared ancestry?
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