Only someone with the strongest self-control can resist looking, however furtively, at people with deformities. This is not very creditable to the human race, perhaps, but it is best to admit that it is so. A book about human deformities is almost bound to appeal to the voyeur in us, therefore, even if we feel that it ought not; but I am glad to report that Dr Leroi’s book is genuinely instructive and enlightening, a brilliant admixture of curious historical anecdote and up-to-date science, written in excellent and often elegant prose. No one need feel guilty about buying it.
Francis Bacon was the first to appreciate that we might discover from the study of deformity something valuable about how the body develops. One cannot help but feel a sense of wonderment that an immensely complex being such as man develops from a single cell, the fertilised ovum. How is it that cells deriving from that single cell, which initially are identical to one another, differentiate into all the different tissues of the body and moreover appear to ‘know’ where to dispose themselves? The study of what happens when things go wrong helps to elucidate this mystery of mysteries.
Dr Leroi, Reader in Evolutionary Developmental Biology at Imperial College, is so good at describing experiments that one turns the page eagerly to learn of their results. For example, he describes a very clever experiment performed in 1930 by an American scientist called Victor Chandler Twitty, who took advantage of the fact that if you cut off the leg of a salamander, it will regrow. Twitty grafted the regrowing limb buds of a large species of salamander, the tiger salamander, on to those of a small species, the spotted salamander, and vice versa.

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