385 million years ago there were fish; by 365 million years ago land tetrapods had appeared. So, evolution predicts that about 375 million years ago there were transitional creatures, with some of the features of finned fish, some of legged land animals. Shubin and his team identified some promising 375 million year old exposed rocks, went fossil hunting, and (after several years of backbreaking Arctic work), found Tiktaalik, just as predicted.
This is a great little tale, not just of that discovery, but of our whole evolutionary heritage: our inner worm, our inner jellyfish, our inner fly, as well as our inner fish. It shows how that heritage can be examined through fossils, through DNA, and through comparative anatomy. And it shows the consequences of that heritage, why our bodies are so bizarre: nerves and bones in the face that twist and turn (because they were originally parts of different structures), nerves controlling our breathing that exit the brain stem and travel precariously through our chest to the diaphragm, rather than taking a better-designed route (because they used to control the gills of our inner, ancestral fish), all features that make a mockery of "design" (intelligent or otherwise), but are perfectly explicable by evolution. I particularly liked the section on illnesses that can be traced directly to this evolutionary heritage (the ills that flesh is, literally, heir to): obesity, heart disease, varicose veins, hemorrhoids, choking, sleep apnea, hiccups, hernias; even mitochondrial diseases from when we were single-celled!
All this is told in a readable style
that brings to life not only our deep past, but also the excitement and beauty of science. It is rather American in flavour (referring to sports I know only by name, and cars I've barely heard of, for example), but nevertheless I just wish it had been longer.
Humanity’s status in the cosmos can seem insignificant. Yet, as Neil Shubin shows, the one place where the universe, solar system and planet merge is inside your body. Exploring the smallest atomic structures and vastest reaches of space, Shubin uncovers a sublime truth: that in every one of us lies the most profound story of all – how we and our world came to be.