Marriage, said JB Priestley, is a long dull meal with pudding as the first course. This book is a bit like that. The dessert served up in its early pages is zesty, with lots of good stuff about what happens when you eat only raw food (you starve to death), but then the reader is obliged to champ through a set of dishes heavier on seasoning than on substance. The repast culminates in a series of idiosyncratic amuses-bouches, with claims that cooking led to our leaving the trees, to sex roles, to marriage, to emotional restraint, to consciousness, and to society itself (which seems unlikely even if Gordon and Barack did bond in a New York kitchen).

Anthropologists have a fatal tendency to decide, without much evidence, what made us human  we have been the upright ape, the grasping, the naked (or, in one recent volume, the well-dressed) one; the handy, the thinking, the babbling, the dishonest, the co-operative and more  and now we are the ape that bakes, barbecues, blanches, boils, broils, braises and browns (Nigella Lawson, quoted on the cover, finds it "absolutely fascinating").

As in the blessed Nigella's own recipes, Richard Wrangham's ingredients are freshly gathered from an impressive variety of fields. He takes us from the amaranth to the zucchini of gustatory biology. Some of his facts are eccentric: in New Guinea, "if a man takes his sago fork out of his hair . . . he is asking for sex"  and had I hair or a sago fork, I would at once take that advice. Many more are intriguing. The BBC once persuaded a dozen people with high blood pressure to go on an Evo Diet  to eat like chimps  at Paignton zoo. Raw cucumbers did wonders for their blood pressure, but although they stuffed themselves the experimental apes all lost weight.

There are lots of "raw-foodists" in Germany and although some are happy to eat uncooked meat they, too, shed pounds and their women cease to ovulate (which, in evolutionary terms, is bad news). The uncooked diet is, even so, a help to slimmers (and those with obese dogs might persuade them to Barf  to eat biologically appropriate raw food  which is healthier than the boiled muck they are usually fed).

Homo sapiens is the culinary primate. Compared to apes, we are gutless; small mouths, weak jaws, modest stomachs and a large intestine only half the size of that of our relatives. Cooking means that food is in part digested before it gets into our mouths. Wrangham has sampled the menu at the Chimpanzee Restaurant, and is not impressed. Many tropical fruits, luscious as they appear, have less sugar than a carrot and some of the apes' favourites taste of mustard oil, while others caused his tongue to freeze as if he had been to the dentist. They need lots of chewing too.

Boiling and frying, as Mrs Beeton put it, "render mastication easy". We spend no more than an hour a day chewing (which leaves plenty of time for doing other things), while chimps grind their teeth for more than half their waking hours. Mastication works, for experiments with tame pythons show that pureed rats are digested more effectively than those in their native state.

More important, heat frees up lots of good stuff for our own use. Internal liquids sucked from patients with a hole in the small intestine show that we digest cooked starch far better than raw starch. The same is true for proteins. Arnold Schwarzenegger in his muscular days swallowed raw eggs for breakfast (and the recommended dose for a body-builder was three dozen a day) but he would have become even beefier had they been boiled first.

The way to man's brain was through his stomach. Primates with smaller guts have larger brains (and brains are expensive), and ours is the smallest of all, probably because cooking liberated our intestines from a large part of the drudgery of digestion. The spare energy went straight to our heads.

Wrangham's "muse of fire" appeared, he suggests, as much as 1.9m years ago. If so, the first Mrs Beeton was not yet human (and there has certainly been some evolutionary backtracking among her televisual descendants). However, the recent excitement about Ardipithecus, our 4.5m-year-old female predecessor, reduces the impact of his claims that cooking brought us down from the trees and made us what we are, for she, more than 2m years before the first edition of Household Management, was already walking upright.

The problem with making grand theories about the past is that they often rest on too few facts. In spite of the tasty morsels scattered through this book, towards its end Wrangham sinks  like so many before him  into the swamp of sociobiological speculation. Another culinary quote comes to mind: Prince Henry on Falstaff's bar bill for two gallons of wine at five and eightpence to accompany a single capon and a slice of bread  "O monstrous! but one half-penny-worth of bread to this intolerable deal of sack!" The bread/sack ratio in anthropology has always been low (and in plenty of places is much lower than it is here), but Catching Fire fails to ignite in its thesis that cooking is the driving force behind all our attributes. Lawson's comment is justified, and the book is fascinating indeed; but it also offers plenty of empty calories. In the words of the starving through the centuries: give us bread!

Steve Jones's books include Darwin's Island: The Galápagos in the Garden of England (Little, Brown).