Darwin remarked on the tendency of organisms to re-express ancestral forms. Sorry, I don't have a citation, but I do remember some commentary about this by Ste

Darwin remarked on the tendency of organisms to re-express ancestral forms. Sorry, I don't have a citation, but I do remember some commentary about this by Stephen Jay Gould. It should be pretty clear to anyone following embryology that a lot of really ancient genes are still present in modern animals, waiting to be re-awakened when the time is right. It is possible that some evolutionary paths are unlikely to be trod more than once by the same organism, but it hardly seems worthy of being called a "law." Around the turn of the 20th century there was a lot of confusion and people still proposing non-Darwinian explanations of biology, so I'd be suspicious that this was just another example of that.