Mutants by Armand Marie Leroi

Armand Leroi is not yet a household name but he soon will be, if Mutants wins the following it deserves. The discovery of a distinguished scientist who can write with such flair and style is cause for rejoicing.

Armand Leroi is not yet a household name but he soon will be, if Mutants wins the following it deserves. The discovery of a distinguished scientist who can write with such flair and style is cause for rejoicing.

It's not easy to make developmental biology - the mysteries of the embryo's progression from single cell to new-born baby - into a riveting read. But Leroi manages to inform and intrigue, by turns. In places, his book, and the three-part Channel 4 documentary that accompanied it, are downright gruesome. Leroi's approach is to describe, in hideous detail, the deformities of development that afflict the human form.

He concentrates on historical examples, and the myths they perhaps inspired: the cyclops, mermaids, hermaphrodites, dwarfs and giants. A huge cast of afflicted humanity, variously feted in royal courts, consigned to fairground freak-shows, and dissected and displayed by scientists and medics, is relentlessly catalogued. Leroi's mission is to make us realise how incredible it is that most of us are born with the usual number of heads, limbs, fingers and toes.

He vividly conveys the wonderment of embryos as self-organising entities, which - like sci-fi aliens - invade women's bodies and take root there. A scientist with an evolutionary perspective, he's also keen to stress the commonalities between us and other animals, and his focus is on the genes shared between salamanders, mice and men.

Mutants - genetic mistakes - fascinate because of what they reveal about the logic of an embryo's self-assembly plan. To date, researchers have pinpointed a few dozen genes that control key developmental pathways. Leroi refreshingly rejects the usual metaphors of linear hierarchies of command, and talks, instead, of "a reciprocal flow of information as precarious as the flow of batons between two jugglers standing at opposite ends of a stage". But each refinement of a developing toe or hair follicle requires "subtle negotiations, the nature of which we scarcely understand".

The TV series of Mutants was powerful, but the book is better. The author does not intrude; this is no memoir of exploits in the laboratory. What's more, against convention, Leroi largely resists the temptation to pronounce on bioethical matters.

Contentiously, he reveals what he would like to know more about. "Racial" differences - the tiny fraction of the global genetic variation that distinguishes people in different parts of the world - fascinates him. The search for gene variants known as Aims, or "Ancestry Informative Markers", is already well under way. Second on his wish-list is the genetics of beauty. If mutations give us misaligned teeth, graceless noses and asymmetrical ears, perhaps the true meaning of beauty is "the relative absence of genetic error".

Leroi remains sanguine, as "Reasonable people know that the differences among humans are so slight that they cannot be used to undermine any conceivable commitment to social justice". Watch this space; Leroi must surely venture again into the perilous waters of media science.

Gail Vines