All first episodes have to be advertisements for themselves - but rarely can the principle have been taken quite as far as with the new popular science extravaganza The Human Body (BBC1) , which has already been presented on a tsunami of hyperbole. It is, some say, the most expensive science programme the BBC has ever made, first fruit of its highly contentious production deal with the Discovery Channel. It has involved the invention of new filming techniques and has straddled the globe in search of novel locations. Usually such publicity barrages stop when it's time for the programme itself to go over the top, but not this time. After a tracking shot across what looked like an unusually representative nudist camp the advertising and incitement began all over again, with Professor Robert Winston punting what was to follow as the thrill ride of the summer season.

There are two obvious commercial models for the advert the producers made. The first would be the recent Bupa campaign, which flattered prospective clients with a series of astounding facts about the human body. As I recall the copy line went something like "You're amazing - we want to keep you that way". The second would be Discovery's own on-air promotional spots, in which a miscellaneous selection of people state an amazing fact about bats or geography or space exploration. This picture of human variety is slightly disingenuous, incidentally - because at a conference of science producers I recently attended a Discovery executive confessed that the demographic bullseye at which all their programmes aim is a twelve-year- old boy. Everything that you see on the Discovery channel must be able to pass through that comprehension bottle-neck.

By and large, 12-year-old boys prefer facts to arguments. Facts, particularly gross or startling facts, have a playground currency which arguments do not. And on this front The Human Body did not disappoint, leading off with a long string of statistics about the life of a representative human baby. She would, we were told, dribble 145 litres of saliva before her first birthday and breath three and a half million balloons of air by her 21st (an unusual unit of measurement prompted by the party used to illustrate this milestone). She'll shed 19 kilogrammes of dead skin and blink her eyes 415 million times. I confess that my own blink output was beginning to slow by this time, as this random informational assault began to have a numbing effect. My condition wasn't helped by the programme's deference to the images they had collected; in one striking sequence in the Yellowstone National Park Winston took one and a half minutes of precious airtime to utter just three short sentences - communication surrendering to the bubbling, primordial scenery. At another point he delivered a link from inside a tank at the London Aquarium - not because this illuminated his argument in any way but simply because he happened to be talking about fish at the time. This was the first real test of the film-maker's ability to convey something more complex than mere astonishment and they did not pass with flying colours.

It isn't all bad news. There are ideas here, about human evolution and the subterranean complexity of human processes, which such techniques may well bring to a wider audience. Some of the film is genuinely wonderful, too - the sight of a peristaltic wave swelling up beneath the lens and then rolling away down the dank tunnel of the intestine would probably quiet the most disgruntled critic. What's more Winston's bedside manner is very good, as reassuring on screen as it must be when he's about to tinker with a patient's fallopian tubes. He concluded with a humanising reprise of the statistical hoop-la - showing you an array of buckets which represented the tears an average human would shed in a lifetime and then reminding you of the rich emotional mystery behind that slopping liquid. If The Human Body can bring those kinds of skills to bear on something more coherent than a string of facts then the product might actually match up to the striking commercial.