Why don't more animals have opposable thumbs?

On a recent kayaking trip, CrowdScience listener Lanier sliced through his right thumb, putting it out of action for a while. This made life difficult, as he couldn’t button his shirt, tie his shoelaces or type efficiently on his smartphone. Missing the use of his thumb made him wonder: since opposable thumbs are so advantageous to those of us who have them, why didn’t they evolve in more species? Host Marnie Chesterton unpicks the evolution of our own unique thumbs with the help of paleoanthropologist Tracy Kivell, learning how our grip compares to that of other animals. We discover why mammals like horses and dogs have no use for thumbs, and why we humans don’t have opposable big toes. Meanwhile, at Taronga Zoo in Sydney, Australia, senior keepers Tarryn Williams Clow and Bec Russell-Cook introduce us to two different marsupials. Humphrey the koala has not one but two thumbs on each hand. Why did koalas develop this anatomical quirk when their closest living relative, the wombat, has spade-like digits? Dr Mark Eldridge from the Australian Museum shares his hypothesis. And what if we, too, had another thumb? Marnie tries on a robotic Third Thumb, built by designer Dani Clode. Dani has collaborated with neuroscientists from the Plasticity Lab at the University of Cambridge. She tells us what the Third Thumb has revealed about the human brain and how we control our digits. Presented by Marnie Chesterton Produced by Cathy Edwards and Margaret Sessa Hawkins for the BBC World Service (Photo: Kung-Fu Koala - stock photo Credit: Alex BOISSY / Getty Images)

You can listen to Why don't more animals have opposable thumbs? online on Radio and Podcast. Open the player on this page to stream the available audio.

Why don't more animals have opposable thumbs? is an episode from CrowdScience by BBC.

This episode is 26:28 long.

This episode was published on Feb 20, 2026.

Yes. Use the heart button on the episode page to add it to your favorite episodes list.

Yes. This page shows related episodes from CrowdScience when more episodes are available from the podcast feed.