Embryological evidence of evolution
The embryological evidence are based on the comparative study of embryonic development of different living beings. The early stages of embryonic development of different vertebrates are very similar, indicating that they come from a common ancestor. As embryos develop, they differentiate. The most related species have more similar stages of embryonic development.
The embryos of vertebrates as diverse as fish, birds, turtles, humans, etc., are similar, with tail and gill slits, although later only fish develop gills. The rest are differentiated as their development progresses.
The study of the embryos of the different vertebrates provide information on the evolutionary development of these species, since they are the same in the early stages of development. As embryonic development progresses, the embryo of each species is differentiated, being more similar the greater the degree of kinship of the species.
Haeckel summed up this theory with the famous phrase " Ontogeny recapitulates phylogeny".