Last Night's Television: Horizon, BBC2<br />Natural World, BBC2

"It's a very young field," somebody said about gerontology in the Horizon film "Don't Grow Old". I expect this is a bit of a chestnut at gerontology conferences, one of those jokes that you hope will die soon but just keeps staggering on from year to year. It doesn't even seem to be true, either, since it wasn't long before the voiceover was explaining that scientists have known for at least 80 years about the life-extending properties of a low-calorie diet. Apparently, laboratory mice, which don't have a choice in the matter, manage to stick around for up to 30 per cent longer if they spend their lives in a state of permanent starvation. As a result, there are people who do have a choice, and should know better, who have adopted calorie slashing themselves, apparently untroubled by the fact that the extra 30 per cent of life you get is at least 60 per cent less worth living. You can't even have a drink to take your mind off the boredom. David Sinclair, first seen here tucking into something that looked unhealthily delicious, had had a far better idea: find out what starvation was doing to the body and see if you could find a drug to mimic it. Preferably one that you can grind into powder and sprinkle over a Châteaubriand with hollandaise sauce. He recently sold his company to GlaxoSmithKline for $270m, which rather suggests that they think he's pulled it off. In the meantime, he's already started taking the substance called resveratrol, which he thinks will do the trick: "It's still an investigational molecule," he said cheerfully, "but I felt the science was strong enough for me to take that risk."

He wasn't the only scientist here who had a personal stake – commercial and emotional – in the elixir of life business. Bill Andrews, who described himself as "obsessed with trying to make certain that I'm around in 500 years from now", was convinced that the solution lay in telomeres, a kind of lace tag at the end of your chromosomes that shortens every time you make a copy in cell division. He was spending around $25,000 a year to take a nutraceutical called TA65, which is said to extend the length of your telomeres, and using the extra days he had to discover something that would do it even more efficiently. He seemed unperturbed by recent research that ageing might not actually have anything to do with telomeres at all. More intriguingly, a New York scientist had isolated three genes that were over-represented in centenarian Ashkenazi Jews, cheerfully tucking into the lox and cream cheese at the age of 102, in a heartening rebuke to the self-starvers. Without consciously knowing it, they seemed to bear out the research of the American psychiatrist who discovered that if you stopped treating old people as frail, incompetent invalids, most of their physical symptoms improved. Enjoy yourself, it's later than you think. It's a damn sight cheaper than TA65 and even if it doesn't work, it's more fun in the meantime.

Don't spend a whole hour of what's left of your life on Natural World, if you missed it first time round. "Prairie Dogs – Talk of the Town" had a natural lifespan of about 20 minutes, which had been stretched to an slightly testing 60 by the television equivalent of calorie-slashing; forcing you to chew every substantive mouthful at least 30 times before you were allowed to swallow and move on to the next bite. The pizzicato strings and the Rob Brydon voiceover told you within five seconds that this was supposed to be one of those perky, family-friendly nature films with a high cuteness quotient, but I'm afraid the prairie dogs turned out to be a B-list meerkat, somehow lacking the charisma and cool of their African counterparts. The film followed the research of Professor Con Slobodchikoff, who'd established – with the help of a plastic coyote and a stuffed badger – that prairie dogs have different words for the different predators that threaten them. He also believed that they had adjectives and different words for colours, though his attempts to establish this fact looked distinctly unconvincing to me. It wasn't entirely clear either how he could be certain that his subjects weren't saying, "Do you really expect us to believe that thing's a real coyote?" Perhaps the most interesting finding was that prairie dogs communities have neurotics who just yip away randomly at everything that moves, driving all their fellow prairie dogs nuts. "In the field, we call those Nervous Nellies or Worried Willies," said one of Professor Slobodchikoff's colleagues solemnly, revealing that the technical language of this field of study was considerably less daunting than some of that encountered in gerentology. By the end, I felt about 10 years older, but then I spotted a silver lining. Think about it – comedy badgers, talking animals, a plastic coyote. Harry Hill should have a field day on TV Burp.