Science, Tech, Math › Animals & Nature What Is Embryology? It can shed light on how a species evolved or how species are related Share Flipboard Email Print Brand X Pictures/Getty Images Animals & Nature Evolution History Of Life On Earth Human Evolution Natural Selection Evolution Scientists The Evidence For Evolution Resources Amphibians Birds Habitat Profiles Mammals Reptiles Insects Marine Life Forestry Dinosaurs View More By Heather Scoville Science Expert M.A., Technological Teaching and Learning, Ashford University B.A., Biochemistry and Molecular Biology, Cornell University Heather Scoville is a former medical researcher and current high school science teacher who writes science curriculum for online science courses. our editorial process Heather Scoville Updated August 15, 2019 The word embryology can be broken down into its parts to create a clear definition of the term. An embryo is the early form of a living thing after fertilization has occurred during the development process but before birth. The suffix "ology" means the study of something. Therefore, embryology means the study of early forms of life before birth. Embryology is a vital branch of biological studies because an understanding of the growth and development of a species before birth can shed light on how it evolved and how various species are related. Embryology is considered to provide evidence for evolution and is a way to link various species on the phylogenetic tree of life. Human Embryology One branch of embryology is human embryology. Scientists in the field have added to our knowledge of the human body by discovering, for example, that there are three major embryologic categories of cells, called the germ cell layers, in our bodies. The layers are: Ectoderm: Forms the epithelium, the thin tissue that creates the outer layer of a body's surface and lines the alimentary canal and other hollow structures, which not only covers the body but also gives rise to cells in the nervous system.Endoderm: Forms the gastrointestinal tract and associated structures involved in digestion.Mesoderm: Forms the connective and "soft" tissues such as bone, muscle, and fat. After birth, some cells in the body continue to proliferate, while others don't and remain or are lost in the aging process. Aging results from the inability of cells to maintain or replace themselves. Embryology and Evolution Perhaps the best-known example of embryology supporting the idea of evolution of species is the work of post-Darwin evolution scientist Ernst Haeckel (1834--1919), a German zoologist who was a strong proponent of Darwinism and proposed new ideas about of the evolutionary descent of human beings. His infamous illustration of several vertebrate species ranging from humans to chickens and tortoises showed how closely all life is related based on major developmental milestones of embryos. Errors in Illustrations After his illustrations were published, however, it came to light that some of his drawings of different species at varying stages were inaccurate in terms of the steps those embryos go through during development. Some were correct, though, and the similarities in species' development served as a springboard to propel the field of Evo-Devo into prominence as a line of evidence supporting the theory of evolution. Embryology is an important cornerstone of biological evolution and can be used to help determine similarities and differences between various species. Not only is embryology used as evidence of the theory of evolution and the radiation of species from a common ancestor, but it also can be used to detect some types of diseases and disorders before birth. It additionally has been used by scientists around the world working on stem cell research and repairing developmental disorders. Sources Robinson, Gloria. "Ernst Haeckel: German Embryologist." Encyclopaedia Britannica.Klatt, Edward C. "Embryology." The University of Utah.