Walk (Radio 3, Sunday) was a mildly pretentious look at what our peculiar method of locomotion has come to mean in the 20th century when, in Patrick Wright's phrase, it has "been reinvented as a philosophical investigation perched on legs". He'd gathered an impressive - or depressing, depending on your point of view - amount of evidence in support of this statement: Richard Mabey on walking as a means of staking out territory; Richard Long reciting one of his walking poems (and coming across, in the absence of any visual stimulation, as surprisingly pedestrian); Richard Holmes on following in the footsteps of Coleridge and Wordsworth, and feeling how the rhythms of their walks infected their poetry; Iain Sinclair (I assume - names and voices weren't always easy to connect) on following in the footsteps of William Blake, and seeing how his rambles through London were bodied out in the rambling visions of "Jerusalem"; and Tom Paulin on the vocabulary of walking - sauntering, "soodling", "going on the dander".
At times, we seemed to be wandering away from the path, and it ended in a very flat-footed fashion, with a poem about, roughly, a Czech performance artist walking from Rimbaud's grave to William Blake's. The programme was at its best when it kept its feet firmly on the ground, standing on particular examples. Mabey, for instance, sounded sententious on the subject of walking as territorial claim, because he talked in general terms; the same point sounded far more convincing when Tom Paulin conjured the spectre of Drumcree (he was also good on the strangeness of walking in woods for someone brought up in unwooded Northern Ireland). And the sheer weight of data offered on the connection between poetry and walking made that persuasive; nobody mentioned it, but presumably this has something to do with why lines are divided up into feet.
Still, you did feel that all this emphasis on the spiritual significance of walking obscured a more important point - it's mechanical significance. We didn't, after all, evolve into bipedal animals because it made us into more effective poets but because it offered us some selective advantage at some time in the past. This is one of the main topics of Slaves to Nature (Radio 4, Thursday), a three-part stroll through current ideas about human evolution. Last week we got the latest thinking on uprightness, which is that it was a good way of regulating body temperature as the African climate warmed up a few million years ago: walking upright exposes less of your body to the noonday sun and more of it to cooling air-currents; it also uses less energy than knuckle-trailing. Once this was sorted out, too, we could stop panting quite so much, which made speech possible.
All this was plausible but somehow rather dissatisfying. Much more exciting was this week's suggestion that what gave Homo sapiens the edge over other hominid species was that we developed needlework. You can evolve all the layers of subcutaneous fat you like, goes the thinking, but if somebody else has come up with a decent shirt then once the next ice age rolls in they're going to be laughing at you. It's irrational, I know, but I somehow feel I ought to learn to knit.