According to embryology, all vertebrate embryos follow a common developmental path due to their common ancestry. All have a set of very similar genes that define their basic body plan. As they grow, the differences that will distinguish the embryos as adults become more and more apparent. The study of this development can yield insights into the process of evolution. This branch of embryology that compares and contrasts embryos from different species is called Comparative Embryology. Even before Darwin proposed the theory of evolution through natural selection, Ernst von Baer claimed that the more closely related any two species are, the more similar their development. Von Baer, who discovered the mammalian egg as part of his detailed studies on animal development, observed that vertebrate animals, during the early stages of their embryological development, seem to have a common design, whereas the adult forms show difference. Arm buds from different species, for example, are virtually indistinguishable when they first form on the embryo, yet they may develop into a wing, an arm, or a flipper. As the fertilized egg transforms into an adult, the general vertebrate plan is modified during growth as each organism acquires its adult species pattern.
Comparative Embryology
According to embryology, all vertebrate embryos follow a common developmental path due to their common ancestry. All have a set of very similar genes that define their basic body plan. As they grow, the differences that will distinguish the embryos as adults become more and more apparent. The study of this development can yield insights into the process of evolution. This branch of embryology that compares and contrasts embryos from different species is called Comparative Embryology. Even before Darwin proposed the theory of evolution