Evolution seems so obvious today that it is hard to understand why it took so long for it to become widely known. In essence, evolution can be summed up with the phrase “descent with modification.” In every generation more offspring are produced than an environment can support, so there is a ruthless culling of all but the best adapted. Even small advantages can have big results if they allow an individual to survive long enough to reproduce and pass on their genes. Eventually, as generations pass, species become better and better adapted to their environment. No angels, no demons, no supernatural forces required.
This book focuses not on the grand sweep of evolving life, but on specific examples of changes over time. It looks at the fossil record of animals such as fish, whales, birds, horses, and good old homo sapiens and his predecessors. Each of these has its own fascinating story of change and survival, and the fossil record, while not complete, clearly shows the accumulating changes over time. In birds, for example, feathers that originally evolved for warmth and coloration displays gradually provided a gliding capability when paired with forelegs modifying into wings. Once these changes indicated clear survival advantages, other adaptations were selected for, such as lighter bones and stronger flight muscles. And thus, slowly and over a very long time, one family of reptiles became birds. It is an amazing story, and the stories of the fish, the whales, and the hominins are just as interesting.
It is also a story of the people who made the discoveries. For a very long time religion seemed to provide all the answers: marine fossils in strata high up in mountains? – Noah’s flood, of course. A multitude of subspecies, each perfectly adapted to its own niche environment? – why, it’s God’s plan, can’t you see? The many similarities between humans and apes? – You should stop asking questions, heretic.
Solving the puzzle of evolution took not only intelligence and determination, but also the courage to question religion. It happened slowly, one generation’s answers building upon those that went before, until finally Darwin (and Alfred Russell Wallace, independently) put all the pieces together, and then it seemed so obvious. When Thomas Huxley read Origin of Species he couldn’t believe he had not thought of it himself.
This book provides an excellent introduction to how evolution works, and its examples are clear and informative. It should – but it won’t – put to rest the old claim that there are no transitional fossils, because the people who cling to religious explanations will not read books like this anyway. You should read it, though. It’s well worth your time.