Review: Rise, take up thy knuckles, and walk

WHEN YOUR contributors are discussing the finer distinctions between Robust Australopithecinae and Gracile Australopithecinae (try saying that after a palaeontologist's party) then the scope for playfulness would seem to be limited. The matter of Christopher Hale's Horizon (BBC 2), a complicated argument about human evolution, required a fair degree of concentration if you weren't to get hopelessly lost, but even so he managed to slip in the odd joke, noting, for instance, that the little stick figure on New York pooper-scooper signs looks remarkably like a knuckle- scraping primate. Thus the rear end of a dog can cancel out three million years of evolution.

It made me wonder whether we might have evolved towards bipedalism simply to get away from all that zebra dung on the ancient savannah, but the truth is apparently more complex. So complex, in fact, that the scientists still can't quite agree with each other. In Search of Our Ancestors, which has just finished on the same channel, put forward the ideas of Don Johansen about our origins and, in particular, about why we reared upright all those years ago. Horizon's 'Some Liked It Hot', following hard on his heels, appeared to suggest that Don Johansen had got it wrong. This is, I suppose, an honest demonstration of the volatile nature of scientific speculation but, tangled between a half-remembered theory and a half-understood one, I'm not sure how cheerful I feel about that.

The disagreement seemed to hinge on whether Lucy (the hominid fossil Johansen discovered) was a direct relative of modern man or merely a kissing cousin. This will not matter to most viewers (she isn't likely to turn up for Christmas either way) but the answer has a bearing on the question of what particular evolutionary pressure first made us walk upright. In biological terms, standing on our own two feet doesn't seem to make sense - it's clumsier and slower than going on all fours, more destructive of the joints and no more energy-efficient.

It's true that a leopard can't eat a Big Mac and milk shake while loping through the tall grass, but the evidence suggests that a brain large enough to manipulate a Big Mac followed bipedalism rather than preceded it. Palaeontologist Dean Falk's solution to this conundrum was suggested to her by a man who repaired her car, who pointed out that the size of the radiator determined the size of the engine. So perhaps evolution favoured the upright because they were better able to cope with the heat (you can imagine a hairy female murmuring 'You're so cool' to a passing biped). And the addition of a cranial radiator then removed the thermal limits on brain growth. As is often the case, there was enough evidence to suggest that this could be true but not quite enough to clinch it. Now I want to hear what Don Johansen's got to say for himself.

Men of the World (BBC 1) provides more evidence for my Comedy Theme Tune Theory. This holds that if the principal characters sing the song the show will invariably be terrible. The best comments on this grim new series come from Stephen Moors' policeman, who pops up now and then to offer a hostage to fortune. 'I sometimes find myself staggered at the amount of stupidity there is in this world,' he declares on his first appearance, after scenes in which talented actors shout a great deal. Well said, officer, you think to yourself.

David Threlfall plays a gormless travel agent who, for some unexplained reason, lives with his only employee. The two men appear to have modelled their relationship on that of Cannon and Ball, and the events depicted are entirely artificial, charged with that peculiar hysteria and stupidity which afflicts bad sitcoms. 'Unbelievable, absolutely unbelievable,' says the Police Inspector next time he appears, taking the words out of your mouth again. After a few more minutes of embarrassing noisiness you cut to him once more. He was beating his head silently against the wall, which saved me the trouble.