From Development to Evolution

This is an important watershed in the structure of the book, for we now turn back again from development itself to its evolution. Thus while the previous chapter was largely restricted to the developmental genetics of Drosophila, the present one will range widely across the animal kingdom, to examine the pattern of similarities and differences in the genetic control of development among phyla. I will concentrate, at some points, on arthropods and chordates; but nematodes, platyhelminthes, annelids and others will feature from time to time.

Although the taxonomic breadth is now greater, the approach will still be selective, and still for the same reason: to allow a reasonably indepth treatment of the examples chosen. The particular genetic systems that I focus on in Sections 7.2 to 7.5 all relate to important ongoing research themes and debates; and all have been introduced, to varying degrees, through consideration of their mechanics in Chapters 5 and/or 6. As we proceed through these selected systems, I will attempt to draw at least one important general message on the evolution of development from each; and these messages will then be brought together in the final section.

It is appropriate to recall, at this stage, that one of the main aims of evolutionary developmental biology – as listed in Section 4.2 – is to map developmental genetic control systems onto the phylogeny of descriptive embryologies that we already have for the animal kingdom.