Recapitulation Theory
What are your thoughts about the Recapitulation Theory and the similarities discovered by Ernst Haeckel while observing different embryos from various species?
The recapitulation theory has been mostly discredited by modern biologist. The idea that every stage in a creatures birth development cycle represents a different stage in their over evolution can not be proven and indeed has been easily disproven. The human embryo, for example, never develops working gills. But it does develop gill slits on the side of its head/neck.
The theory, while not literally correct, does have credence in some areas. This is evidence that some things that have been dissolved away by means of evolution can be seen through the embryonic stages. For instance, during a human embryo's cycle, they have a small tail at some point, later that tail recedes and only the tail bone is left before birth.
https://en.wikipedia.org/wiki/Ontogeny_and_phylogeny