"Maybe that's what being human is about," said the presenter, at the end of a documentary that was primarily close-up footage of caterpillars, tadpoles and locusts. I believed him.
David Malone has pulled this trick off before. In 2011 he fronted the BBC4 classic The Secret Life of Waves, a film that began as a fascinating study of the physics of the ocean but ended as a treatise on mortality – how our lives are a process, a beautiful thing made by energy that must eventually dissipate, because moving and changing is living.
Metamorphosis: The Science of Change (Wednesday BBC4; iPlayer) looked at the transformations that take place within us as we live, and our longing for the past, by first observing the phenomenon of radical physical change in nature. Ovid and Kafka mingled easily with the bristling, creeping oddness of sea urchins ripping themselves apart and starting again; or green, solitary locusts acquiring dark battle camouflage and joining deadly swarms.
How does a caterpillar know that this moult isn't just another moult - it's the big one? What makes some tadpoles decide to turn into frogs more quickly? And what do you have to do to a nice green locust to make it nasty? "I've always thought that metamorphosis was... weirdly interesting," said Malone, and how right he was. That a caterpillar and a butterfly can be the same creature with the same genetic code is, when someone as engaged and adept as Malone makes you think about it, among the most wrigglingly bizarre things in the world.
To lay out the facts, Malone enlisted help from jolly nerdy entomologists and beautiful/horrifying micro-photography, but it was his own screen persona, as a teacher who has you hanging on every word, that made the programme sprout wings. Malone has the gift of appearing to have the thought there and then rather than reading it from a script. He often breaks eye contact to summon up the right phrase. At his best, Kevin McCloud does something similar, although Kevin hams up the act by dramatically walking out of shot at the end of every programme.
When we'd learnt that locusts' metamorphosis is primarily one of the mind – a behavioural shift, prompted by a gush of serotonin – and that this can be undone when swarming's no longer expedient, Malone was taken by the desire to muse. We change ourselves, we become new people, we effect changes in technology and society that then turn round and change us. Our metamorphoses are only in our mind but are still profound and frightening. For locusts, read soldiers.
Malone saw glory and tragedy. In Kafka's story, the bug-man Gregor Samsa feels more alive and human than ever when he listens to his sister play the violin, because in his new form he hears it anew. But the change is about to kill him. Being able to alter our identity and circumstances is an immeasurable gift, for individuals and for humanity – "We are the one creature that can redefine the nature of life," Malone's philosopher friend Raymond Tallis told him, as the two of them stood on a beach with an offshore wind farm in the background – but it's one we fear.
"We remember," Malone said. "We can't help but look back, remember the creature we used to be, and regret what we might have lost." The sucker punch was landed. Once again I found myself staring straight through the end credits of a David Malone film, not knowing whether I'd been lifted up or taken apart, but enlivened by it either way.