This new documentary series is classic Channel 4 fare: intellectual but smutty - or, if you prefer, smutty but intellectual. It tells the story of the rise of sex research from Victorian times to the present day, taking in all the usual suspects - Dr Freud, Masters and Johnson, Shere Hite - along the way. There are elderly and not-so-elderly talking heads, some good archive footage and various amusing animations for when things get really, erm, mechanical. But there are also lots of naughty images: women furiously masturbating, men proudly revealing their giant members, that sort of thing. What I'm trying to say is, don't tune in if your mother-in-law is visiting - unless she's the kind of woman who reads Nancy Friday in bed, naturally. Maybe check out her bedside table first.

The material included in the first film, which focused on that mysterious thing, the female orgasm, was broadly familiar to me because I was once sent on assignment to California where, it was rumoured, certain drug companies were close to developing the so-called female Viagra. In the course of working on this story, two things happened. The first was that I learned to keep a straight face while extremely suburban-looking American scientists told me about such things as lubrication, blood flow and the swelling of vaginal walls. The second was that I grew increasingly suspicious of what you might call the medicalisa­tion of sex. It wasn't only that I was concerned these doctors were going to make an awful lot of money out of "fixing" something that might not have been broken in the first place. It was their intense interest that bothered me. Why are some doctors so obsessed with the female orgasm? Shouldn't they find the cure for can­cer first?

The Sex Researchers (starts 16 June, 10pm) does not alleviate this anxiety, and how could it? One of those interviewed is Cindy Meston, from the University of Texas in Austin. Dr Meston wears a white coat to work, which is fair enough, I suppose. Slightly more alarming, however, is that her little dog wears one, too; it has his name and title - "laboratory assistant" - embroidered on it in red silk.

Would you let a woman whose dog wears a lab coat stick a probe up your vagina? No, I wouldn't, either. Meston wants to find out why women don't have more orgasms, which seems to me to be a futile project; I'm not sure most of us feel such a lack and, even if some do, it's hardly a matter of life or death. Then again, her little project is possibly not quite so futile as the work of Meredith Chivers. This Canadian researcher has discovered that women get moderately aroused when watching footage of bonobo monkeys mating. Hmm. Lie back and think of the bonobos. Remember where you heard it first, girls.

The film is at least replete with wonderful, and extremely weird, facts. Victorian men sent their randy wives to the doctor to have their genitals massaged, a treatment that proved to be strangely popular. Some of them - the husbands, I mean - also wore spiked metal rings to deal with unwanted erections of their own. In the 1920s, you could buy a mechanical vibrator that could be attached to any electric light socket. The doctor, writer and social reformer Havelock Ellis, who died in 1939, got turned on by the sight of women urinating and not very much else, and was once told by a prostitute about a client of hers who could achieve climax only if he was able to watch a pigeon having its neck broken at the same time as he was having intercourse.

On their own, such items of trivia make for great dinner-table conversation (I'm also looking forward to telling my girlfriends about the bonobos over pasta and a glass of red). When gathered, however, they suggest to me that most people know exactly what they want and how to get it, and have done down through the ages. The nosy-parker researchers, armed with their horrible probes and their plastic penises, are trying and mostly failing to quantify the unquantifiable, clumsily invading what was once the province only of the poet. l