" He proposed that new evolutionary features were added to the end stages in development; for example, amphibians arose by adding amphibian-specific features to the end stages of the development of a fish ancestor, reptile features to those of amphibians, and so on. Over time, according to Haeckel, this process resulted in embryonic development tracking evolutionary history. "

― Neil Shubin , Some Assembly Required: Decoding Four Billion Years of Life, from Ancient Fossils to DNA