Evolution triumphs because it turns to natural selection, the plodding accumulation of error.

Genetics is to biology what atomic theory is to physics. Its principle is clear: that inheritance is based on particles and not on fluids. Instead of the essence of each parent mixing, with each child the blend of those who made him, information is passed on as a series of units. The bodies of successive generations transport them through time, so that a long-lost character may emerge in a distant descendant. The genes themselves may be older than the species that bear them.

Philosophy is to science as pornography is to sex: it is cheaper, easier and some people prefer it.

The language of the genes has a simple alphabet, not with twenty-six letters, but just four. These are the four different DNA bases—adenine, guanine, cytosine and thymine (A, G, C and T for short). The bases are arranged in words of three letters such as CGA or TGG. Most of the words code for different amino acids, which themselves are joined together to make proteins, the building blocks of the body.