Last Night's TV: No one lifts the spirits like Attenborough, and nothing lowers them like children left alone to reveal the horridness of our species

Charles Darwin and the Tree of Life, BBC1Boys and Girls Alone, Channel 4La Bohème Backstage, Sky Arts

Sir David Attenborough has easily the warmest voice on television, giving off five watts every time he says "species" and making "evolution" whistle like a kettle,so it was worth huddling round Charles Darwin and the Tree Of Life, a beautifully poised biographical account. Illustrative props included the 18-year-old Attenboy's copy of The Origin of Species (sixth edition, bought for a shilling) and a platypus, the David Gest of the animal kingdom.

This special creature looks as if it has not been made by nature's hand alone; in fact, when one first arrived in London in the 18th century people clamoured to know its plastic surgeon. Thankfully Darwin put them right by explaining that it was actually a discontinued animal, made on software nature forgot to update. Possibly I should leave the natural history to Attenbravissimo. He makes it so lucid and toasty.

Boys and Girls Alone is a thoroughly Darwinian Channel 4 reality experiment that puts 20 children aged eight to 12 into isolated holiday accommodation in Cornwall for two weeks and stands well back, only interfering when a tiny person is about to be struck over the head with a garden rake or sob themselves unconscious (both happened in the first 48 hours). Various moral objections have been raised – but realistically, well, worse probably happens at prep school, and for longer. Our surface concern is that it isn't good for the children but deep down we're troubled by what this kind of show forces us to confront: the depressing fundamentals of human nature. It isn't just that the children are horrid – they're horrid in such predictable ways.

The girls make cakes and canapés and conduct bitching campaigns, operating in instinctive unison like a shoal of fish. What's the difference between a 12-year-old girl and a piranha? Chapstick. I would rather go to Cornwall with Pol Pot than a girl between the age of 11 and 13 who thinks she's cool. Two older girls decided to decorate the younger ones' house: a nice gesture, till it transpired that their handiwork consisted of such quotes as: "You will die inhumanely."

The boys shoot one another amiably with water pistols; food-wise, they fend for themselves. Power struggles between two boys who would be king are conducted not by direct combat, but via a proxy – a cuddlier boy who wears glasses. William Golding should get royalties. Nine-year-old Sid cannot boil a kettle (he tried squinting at it for a bit, then tapping it gingerly, but still it did not work) and when he was still hungry by the end of episode one, his mother intervened. The boys have more important things on their minds: drawing up a constitution for waterpistol war: "No fakes ... no team changing ... be respectful ... no hurting animals." The Magna Carta cannot be far off. It does make you wonder, this effortlessly allegorical show, how civilisation ever developed. The children in it are pretty unselfconscious, being of an age where the here-and-now is everything, so, unlike other reality TV shows, this feels experimental. Who knew, for instance, that children swore so much?

"May contain strong language" is an announcement seldom made before a Sky Arts opera broadcast, but on Wednesday it popped up before La Bohème Backstage – a live camera feed from the wings during the first night of the new production by Jonathan Miller. A television first from Sky Arts, it was a magical treat, like taking the back off a grandfather clock and watching the elves at work. We saw rude mechanicals in the gods scattering fistfuls of "snow"; we saw Mimi's quick change into her final death wig, conducted in rapid, grave silence; we saw the backstage percussionist beating out the distant church bells – in some productions he clinks glasses in the tavern scene, too. Often the slightly hapless interviewer would ask someone waiting in the wings who they were, only for them to disappear on cue; the next moment Musetta would flounce offstage, practically elbowing the camera out of her way.

It was the most atmospheric television I've seen for years. To Miller himself, tiptoeing around the wings, silent and wraithlike, unacknowledged by the busy cast, the backstage world is like the machinery of consciousness – "what we all carry round with us". For those who prefer the fourth wall in place, I refer you to my colleague Anna Picard's review from the stalls.