Embryonic Homologies – How Embryonic Homologies Support EvolutionWhat Do Embryos and Embryonic Development Say About Evolutionary Theory?
Most anatomical homologies, whether active or vestigial, are present in the adult members of a species. A few anatomical homologies, however, only appear briefly during the embryonic stage of an animal’s development. These short-lived anatomical homologies are referred to as embryonic homologies and serve as evidence that the species in question is related to other species where the organs or anatomical structures persist past the embryonic stage and through adulthood. As the embryo develops it goes through a variety of stages, many of which show homologies between different species. Bird limbs are an important example of this: birds are tetrapods, all of which have five-digit limbs, but adult birds have a three-digit limb in its wings. This might appear to be a problem until you examine birds’ embryos, and then you will find that this limb develops from a
