Embryology and evolutionary biology are both branches of biological science. Embryology is the study of all aspects of the conception and development of embryos. Evolution is the study of the gradual change of populations via genetic inheritance, as described on UCMP's Understanding Evolution website. The characteristics of Embryos support Darwin's Theory of Evolution.
Embryology and the apparent similarities between embryos of different species are considered evidence of evolution. Charles Darwin noted that the shared characteristics of the embryos of different species could be explained by his theory of evolution, as detailed in chapter 13 of "The Origin of Species." He also asserted that evolution explains structures present in the embryos of many species that later develop and diverge in form and function.
It was later suggested that a better understanding of embryonic development could help scientists understand the mechanisms of evolution and vice versa. For example, the discovery and subsequent study of homeobox, or Hox, transcription factors provided an example of a series of genetic loci that could produce a large degree of phenotypic variability with relatively small variations in the sequence of the genes themselves. Abnormalities in these genes, in addition to providing an example of small genotypic changes resulting in significant phenotypic changes, are also responsible for many disorders that alter the development of the afflicted embryos.