Michael Deacon: Competitive Gareth and super Hans Sing While You Work has some of that. But the trouble with competition is that it makes Gareth... well, competitive. "Yeah, it was nice enough," he grumbled to the camera after the staff at a ferry company had sung for him. But this is a contest. It's not a charitable situation where I'm just being nice to people. Isn't it? Why not? What's the big important prize? This isn't The X Factor, in which countless desperate wannabes beg for a million-pound record contract and the chance to become the most lusted-after pop stars in America, like One Direction. This is just the staff of P&O joining in a sing-song because you've asked them to for the sake of your programme. They haven't pleaded with you to transform them into superstars. You're still a great teacher, though. Just lose that new beard. And the yellow trousers. Not a big fan of the bowtie either, if I'm honest. OK, it's your signature look, maybe we can compromise on that. But definitely lose the new beard. Don't Panic: the Truth About Population (Thursday, BBC Two) was presented by Professor Hans Rosling. Frankly I wish everything was. I just want him to explain things to me. Astrophysics, Cubism, Finnegans Wake, twerking. I don't know whether he's actually an expert in any of those subjects, but I'd still watch. He's just such a good explainer. Partly it's his enthusiasm ("I'm not an optimist, I'm a possiblist"). And partly it's his Swedish accent. Everything is YOOOJ! Mankind faces YOOOJ challenges! But we are making YOOOJ strides! He also says "digital" as "diggital." Now so do I. I'm wearing a diggital watch. I've got a diggital camera. If you make fun of my pronunciation I'll raise my middle diggit. In this programme he explained global population growth. In 1900 there were 1.5 bn people. In 1950, 2.5bn. In 2000 it was 6bn - and some experts think that by 2100 it'll be 11bn. We must be having too many children, right? Actually, no. We're having fewer than we used to. Before 1800, the average woman gave birth to six children. Today she gives birth to 2.5. And I'm not talking about the average woman in the West - I'm talking globally. Take Bangladesh, where the figure 40 years ago was seven and is now 2.2. But, thanks to medical advances, cleaner water and greater prosperity, fewer children are dying, so more of them go on to become parents themselves; plus life expectancy is up, hence unprecedented legions of old people. Cheering and worrying all at once, isn't it. Still, Prof Rosling says we can cope with the ever-increasing demand on resources - provided we in the West are willing to get by on less so the poorer can have more. Hey, how about that. He's got a sense of humour, too. If population growth does lead to disaster, then I fear that, contrary to the title of Richard Hammond Builds a Planet (last Sunday, BBC One), our friend from Top Gear can't save us. He didn't build a planet at all. He just showed us, using fancy graphics, how one might go about it, if one had the right materials. Well, no point sitting here moaning. You get cracking on the core, I'll knock up a continent.