The Developmental Hourglass Model

An Arabidopsis thaliana flowerWe’ve seen plenty of occasions where the science of embryology has been dragged into the creationism-evolution fight, usually relating to Haeckel’s infamous drawings. This topic of debate has tended to stay within the animal kingdom, but a recent paper in Nature gives an opportunity for Jeffrey Tomkins to expand it’s scope into the realm of botany. He writes: Plant Embryo Development Supports Creation. That seems to be a bit of a stretch.

Embryology confuses me, I must admit, but from what I can tell the point of the paper is to report that plants follow a “developmental hourglass” that has previously been observed in animals. They explain:

Animal and plant development starts with a constituting phase called embryogenesis, which evolved independently in both lineages. Comparative anatomy of vertebrate development—based on the Meckel-Serrès law and von Baer’s laws of embryology from the early nineteenth centuryshows that embryos from various taxa appear different in early stages, converge to a similar form during mid-embryogenesis, and again diverge in later stages. This morphogenetic series is known as the embryonic ‘hourglass’, and its bottleneck of high conservation in mid-embryogenesis is referred to as the phylotypic stage.

This is a little different to the straw man that Tomkins portrays when discussing the evolutionary take on the results. But we’re getting ahead of ourselves. Continue reading