What is an example of embryological evidence for evolution?

Answer 1

Embryological development in animals displays the same set of nested hierarchies that is known from comparative morphology and genetics, and thus evidence for common descent.

Nota bene: this adherence to nested hierarchies is not to be confused with the 19th century hypothesis of ontogeny recapitulating phylogeny. Embryos do not go through evolutionary stages during their development, but they dodisplay atavistic developments that are consistent with phylogenies based on other sources.

Answer 2

Embryological development often produces atavistic features that aren't found in the adult form, but are found in more basal forms of the same lineage. An example of this is the pharyngeal arches found in embryological stages of human beings. At one stage, they are indistinguishable from the structures that form gill pouches in other animals - but in mammals, they develop into other structures. Another example is the hind limbs on whales: at some stage during the embryological development of a whale, the embryo forms hind leg limb buds, the same as embryos of the land-based animals from which it descended. Often, such buds are then reabsorbed. Many whales, however, retain some vestigial form of their hind leg bones.

But atavisms aren't the only or even the best example of evidence from embryology: each and every single developmental feature in embryology fits neatly in a pattern of nested hierarchies that permeates all of life at every level of observation. It is this pattern that gives us the definitive proof of common descent, and, more importantly, allows us to determine the lineage of an animal, and its place in the evolutionary tapestry of life.