A Reply to Carl Zimmer on Embryology and Developmental Biology

I recently read Carl Zimmer’s response to my critique of his November, 2006 article in National Geographic. In this post I will discuss Zimmer’s response to me regarding embryology and developmental biology. The embryonic hourglass is the idea that vertebrate embryos (like those of fish, amphibians, reptiles, birds, and mammals) start off developing very differently, converge with some similarities at the pharyngular stage, and then again diverge. I stated in my original article that “vertebrate embryos start off quite differently,” but that “Zimmer’s diagram selectively displays embryos from the encircled stage where they are most similar.” The implication is that this falsifies the idea that evolution proceeds by tacking on new stages of development because these vertebrate groups start off Read More ›