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Classical experimental and comparative embryology is a field that has fallen on hard times until recently. When I attended the University of Arizona there was a full blown course in embryology, both descriptive and experimental. By the time I was a graduate student at the same institution the course had been rolled into Organismic Biology in which all of embryology was loaded into a third of a semester. In essence developmental biology in relation to evolutionary studies gave way to molecular. Still some pretty good work went on in the background that impinged on development and was to result in the discovery of HOX genes. HOX genes (or homeotic genes) proved to be the "organizer" that was postulated by various experimental embryologists such as Spemann. Even more astoundingly they proved to be pretty much the same, no matter which organism was being studied. HOX genes in humans were essentially identical to those of insects! 

This remarkable fact offers proof for the idea that all life is related and that development is a key factor in evolution. In "Endless Forms Most Beautiful" Sean B. Carroll explains the significance of such discoveries as the genetic "tool kit" (including HOX genes) on our understanding of evolution and of development. Indeed, this is a fascinating story that has already caused me to rethink some of my understanding of evolutionary principles. 

We live in an amazing world in an amazing universe. The genetic material made up of DNA is a very remarkable material. What other materials could have developed huge numbers of organisms (as many as 30 million extant) that vary from zebras to sulfur bacteria? Yet that complexity appears to have developed from a very simple beginning. 

Carroll was influenced by Steven J. Gould in his interest in biology, but he does not flinch from disagreeing with Gould about contingency. Carroll says that if the tape of evolution were run again, pretty much the same thing would have happened. I think that I may have to agree to a point (although not as far as Simon Conway Morris goes with it). However, certain alterations in earth history might still have caused a radical change in the outcome, as in the development of a completely water covered planet or a very large asteroid strike (larger that the one that apparently killed the dinosaurs except birds). At the same time not all evolved faunas that developed in isolation from each other resemble each other exactly. The marsupials of Australia, for example, had a number of forms similar to placental mammals. However, there was no exact analog to the kangaroo outside of Australia or of hoofed animals in Australia (giant wombats don't have hooves). I agree faunas can be similar, but not necessarily identical and that intelligent life may be inevitable, but may not necessarily have looked like us or even evolved from mammals. 

That said, evo-devo, as the evolutionary development researchers call it, has much to offer and it certainly cannot be dismissed. This is an exciting time to be involved with evolutionary biology, despite the creationist (or more sophisticated "Intelligent Design") attack on the whole idea. 

This is an excellent introduction to the excitement of a continuing unfolding of evolutionary thought. I recommend it highly.