Achallenge to traditional (pre-1860) ideas about species came from embryology, when it was discovered that a challenge to traditional (pre-1860) ideas about species came from embryology, when it was discovered that all animals develop similar embryonic gills mutations have a far more dramatic effect on embryos than on adult organisms the embryological development of many plants and animals is almost identical embryos of dissimilar organisms, such as sharks and humans, resemble each other the more advanced the a