Do developing embryos recreate human evolution?
I read somewhere that if you were to follow the human embryo from conception to birth, it goes through every stage of evolution that has led to humanity. Is this true of an old wives tale?
Well, this is the old argument which is known as ontogeny recapitulating phylogeny - a rather pompous scientific term. Ontogeny is the development of the individual, and phylogeny is the development of the species. This whole idea that we've come from the sea, and we've come through a process of evolution which has gone from simple single celled organisms right through fish and amphibia - it's basically Darwinism. But the actual stage of an embryo within its mother doesn't actually pass through those phases. What happens is that we resemble past evolution, but we're not actually going through the stages one after the other to get to the stage where we are born.