Six Impossible Things Before Breakfast, by Lewis Wolpert

"If you were to go into the jungle, which would you prefer to have with you, a friend or an axe?" asks Lewis Wolpert. Our ancestors preferred their axes, he believes, and that was what made us human. For Wolpert, the capacity to make tools, entailing a sense of cause and effect, is the basis of the human capacity to hold beliefs. In this, he upholds a tradition that sees man, in Benjamin Franklin's words, as a "tool-making animal".

His publisher is apt, for his account is an affirmation of Homo faber, man the maker, defined by his relationships with physical objects. A blue, white and blue "tricolour" emblazoned with a bird would also have been apt, for this book embodies the spirit of popular science upheld through the middle of the last century by Pelican paperbacks. It is the work of a distinguished scientist reflecting on subjects outside his specialism (he is a developmental biologist). It is imbued with a sense of public service, arising in part from the restraint with which he presents himself as a narrator and the respect with which he discusses perspectives other than his. And his central thesis about tools enjoyed its heyday when humankind was known as Man.

It adds up to an account that doesn't scintillate but fufils one of the principal functions of popular science by providing the lay reader with a good sense of the shape of the problem. The book's worth also owes much to its liberal spirit. Although Wolpert maintains a firm grip on his opinions, they do not exclude him from a circle of friends in which the familiar superstitions of our time flourish. He is sympathetically interested in the beliefs encouraged by other cultures; and what a pleasant change it makes to read an account of evolved psychology that does not sneer whenever a social anthropologist is mentioned.

Less commendable is the lax editorial hand that has allowed him to get away with a clunker such as "Suicide bombers in London have led to further attempts being made to understand their beliefs". This is a rare sign of struggle with religion. His rules of engagement do not permit him to try to persuade people to shed religious beliefs that benefit them.

Although religion only gets a single dedicated chapter, it is the heart of the matter. In this respect, Wolpert's insistence on the exclusive role of tools seems contrary. As Daniel Dennett argues in his new book on religion, Breaking the Spell, an evolved sense of others' intentions must underlie belief in deities, whose supposed intentions are used to explain the unexplainable.

This idea arises from a vision of humans as social animals that now overlies the older vision of the tool-making animal. Intelligence is explained as the result of the evolutionary pressures of living in groups of clever primates. Individuals need to monitor relationships and understand them, to choose their friends and enemies as best they can. The cleverer they all become under such pressures, the greater become the benefits of alliance.

The alternative answer to Wolpert's question is that, eventually, shared beliefs are established about abstractions and gods, creating the confidence that a companion is truly a friend, and thus far more valuable than an axe.

Marek Kohn's 'A Reason for Everything' is published by Faber