Complexity and the Origin of the Metazoa

Abstract

In this chapter I examine the origins of the Metazoa against the backdrop of the evolution of multicellularity in the previous chapter and the discussion of the origin of phyla in Chapter 2. While separating this discussion from that on the origins of phyla in Chapter 2 may seem artificial, it is important to remember that the origins of body plans predated the origins of phyla, by perhaps hundreds of millions of years. Twelve chapters is a small gap in comparison.

‘As any analysis of biological systems builds upon cell theory, an evolutionary analysis of development would benefit from describing evolutionary transformations as changes of the properties and activities of individual cells.’ Sommer, 1997, p. 225