Shapes of Time: The Evolution of Growth and Development

Genetics and natural selection typically take front stage in discussions of evolution. Such has been the case for a long time, and may be for some time to come. BUT in "Shapes of Time," McNamara makes a strong case for including growth development in the mix in deciding how, why, and when organisms came to be the way they are (or were). McNamara's main thesis is that three major developmental trends -- 1) Peramorphosis; 2) Paedomorphosis; and 3) Hypermorphosis (a twist on Peramorphosis) -- produce a good deal of the observable variability out there. He proceeds to make the case that changes in rates of development and growth (i.e., heterochrony) can have a major impact as an evolutionary process, and that heterochrony deserves a more prominent place in evolutionary theory.Just so you know what he's talking about...1) peramorphosis is a condition where growth or development proceeds beyond that observed in the ancestral condition; 2) paedomorphosis is a condition where development does not reach the state observed in the ancestral condition; and 3) hypermorphosis (a form of peramorphosis) is a condition where not only does growth and development surpass the ancestral condition, but growth and development proceeds longer than in the ancestral condition.McNamara does an excellent job of tying together his thesis in the last chapter by applying virtually everything he talked about throughout the book. In that chapter he addresses human evolution, and does a great job of showing how, in terms of heterochrony, we are a "cocktail organism," showing signs of paedomorphosis here, perimorphosis there, and hypermorphosis in another situation.Readers entrenched in the traditional view of the "new synthesis," i.e., genetics + natural selection = evolution, will find themselves shaking their heads here and there as they read this book (I even did that a couple of times and I'm a relatively strong proponent of development being a significant factor in evolution). If you press on you will find that McNamara makes a sensible, supported case for the importance of heterochrony as being an important factor in evolutionary theory.The question I have is this: "What is the source of heterochrony in development?" McNamara doesn't address this directly, but his downplaying the role of genetics suggests that genetic variability codes primarily for what happens, not when or how fast it happens. This is a quandry! What controls and passes on information about the timing of development and growth if not genetics? In any case heterochrony exists in growth and development. That is not debatable. I support McNamara's position that growth and development play a major role in evolution. I wonder what it will take to get those factors included in mainstream discussions on evolutionary theory? Good job to Kenneth McNamara! He provides good food for thought in this offering.5 stars.Alan Holyoak, Dept of Biology, Manchester Coll

A winderful book, well writen, full of exemples and recent discoveries in understanding of the mecanisms driving evolutionary change. Not the common book on natural selection. Startingly fresh and thoughts-provoking! Shoulf be on every biologist bookshelf and is a great intorduction to the extented theory of evolution for anyone.