All about Archaeopteryx Transitional Fossils from the Talk. Similarity of embryos of vertebrates suggest common ancestry. Note that early human embryos have gill slits and rudimentary tails. Vestigial Organs A structure that seems not to have a function in an organism but resembles a functional organ in another type of organism. For example, whales have useless pelvic bones and, occasionally, rear feet resembling those in other mammals.
Some snakes have leg bones.
All life forms based on DNA and 20 amino acids. Individual genes from different species can be sequenced and compared. If you really, really, really want to know how DNA is sequenced. These genes can come from the nuclear, mitochondrial, or chloroplast genomes. Chromosome banding patterns and protein sequences can also be compared.