There are some facts the simple knowing of which seems to me to be a supreme achievement of our species. The fact that we are all made of stardust. The fact that 99.9999999999999 percent of all matter is empty. The fact that mass and energy can be expressed in terms of each other. Stuff like that.
Pre-eminent among these to me, for sheer mind-expanding awe, is the fact that life on this planet has developed precisely once, as far as we know, and everything on earth has evolved from it. That means that when you go outside and lie down in the garden, everything you can see and hear – people walking nearby, their pet dogs, the squirrel darting past, the birds you can hear tweeting, the insects and tiny bugs crawling around underneath you, the trees the birds are standing on, the grass you're lying on, the bacteria in your guts – all of them are your cousins: you're quite literally related to them in the real, genealogical sense.
If you go far enough back in time, in other words, you will eventually find a creature whose descendants evolved into both squirrels (say) and people. Indeed, the rules of heredity being what they are, you could even find a single individual
who was a common ancestor to every squirrel and human alive. And indeed such an animal really did exist, around 75 million years ago in the Upper Cretaceous. It probably looked sort of mousey, and Dawkins estimates that he or she was our ‘15-million-greats-grandparent’. Squirrels are not ‘closer’ to this creature than humans are: we and they are equally related, having been evolving independently for the same amount of time.The Ancestor's Tale
takes exactly this approach to exploring evolution. It starts with humans and works backwards – looking first at the common ancestor between humans and chimpanzees, and continuing until we reach the common ancestor of all life on earth. Dawkins's word for a common ancestor of more than one species is ‘concestor’, and there are only about 40 of them (!) between us and the origin of life more than three billion years ago. The Cretaceous mammal I mentioned above, which evolved into us and squirrels (along with all the other rodents, lagomorphs and primates), is Concestor 10 according to this schema.
I think there's a lot of traps you can fall into when you start thinking about evolution. It's easy to feel, instinctively, that evolution is somehow teleological: that it's been working towards
– if not us, then at least creatures that are increasingly complex and increasingly intelligent. But that of course is not the case. Things survive that reproduce themselves well, and there are plenty of single-celled organisms still with us that have seen no need to get any more complicated for millions of years. Bacterial life is in fact astonishingly varied and rich, whole phyla of creatures that branched off before multicellular life even came about; indeed, chemically speaking,
we are more similar to some bacteria than some bacteria are to other bacteria.
Just think about that
for a second.
Before Dawkins got distracted by religious idiocy, he was well known as being one of the scientists most able to explain complicated ideas in a fresh and accessible way. All his skills are on display in this work. It's not just the zoology and the evolutionary biology, where you'd expect him to be strong; there's also a fantastically lucid explanation of the biochemistry within a cell, and even one of the best explanations of the physics of radioactivity that I've come across. He is calm and careful; he repeats himself where necessary; he shares several teacherly witticisms; and he does all this without ever condescending to the reader. He allows paragraphs of complex material to sit, so that you can read and re-read them a few times before he carries on. Occasionally he cannot stop himself breaking out in exclamations of wonder or poetic meditation – as when he discusses the fossilised footprints of three early hominids from some three-and-a-half million years ago:
Who does not wonder what these individuals were to each other, whether they held hands or even talked, and what forgotten errand they shared in a Pliocene dawn?
His enthusiasm is infectious. The whole book is a fantastic exploration of this most beautiful piece of modern human understanding. It's full of astonishing anecdotes and scientific details about the natural world, but it also all ties together into a conception of life that's more awe-inspiring and more moving than any supernatural system could ever be.