Do pandas have thumbs?

Published 12 October 2026 · Last updated 12 October 2026 · Last reviewed 12 October 2026 · By the PandasWise team

Pandas do not have a true thumb, but giant pandas have something that works like one. Alongside five ordinary fingers, each front paw carries a greatly enlarged wrist bone called the radial sesamoid. It juts out from the palm like a sixth digit, and the panda presses bamboo against it to hold stems while it strips and eats them. Scientists call it the false thumb, or the pseudo thumb.

Five fingers plus a wrist bone

Like most carnivores, a giant panda's five fingers lie side by side and cannot be folded across the palm the way a human thumb can. That is a problem for an animal that spends much of its day handling bamboo; see how much bamboo a panda eats. The solution evolution found was not a new finger. Instead, a small bone on the thumb side of the wrist, the radial sesamoid, grew much larger than in other bears. It sits at the base of the palm and gives the panda something to squeeze against.

As a 2022 paper in Scientific Reports puts it, the giant panda has, in addition to the normal five digits, a greatly enlarged wrist bone that acts as a sixth digit, an opposable thumb for manipulating bamboo.

A double pincer, not a single grip

For decades people assumed the false thumb moved on its own, like a real thumb. In 1999 a team led by Endo looked inside a panda hand using computed tomography (CT) and magnetic resonance imaging (MRI), and published the result in Nature. Their three dimensional images showed that the radial sesamoid cannot move independently of the bones it joins. It works as part of a single unit.

They also found it has a partner. On the opposite side of the hand, the accessory carpal bone is enlarged too. Together the two bones form what Endo and colleagues called a double pincer like apparatus on the inner and outer sides of the hand. That arrangement, they concluded, lets the panda handle objects with great dexterity. So when a panda holds a bamboo stem, it is not just pinching with one bump. It is closing its whole hand around the stem with a support on each side.

The oldest false thumb

How long have pandas had this tool? In 2022, Wang and colleagues described fossils of Ailurarctos, an ancestral panda from the late Miocene site of Shuitangba in Yunnan Province, China. Its radial sesamoid was already enlarged and already worked as a functional opposable thumb. The authors say this crude thumb suggests the panda's dedicated bamboo diet goes back as early as 6 to 7 million years ago.

Why it never became a real thumb

The same study offers an answer to an obvious question. If a bigger thumb is useful, why did the panda's stay small? The fossil thumb from millions of years ago is not much smaller than the one living pandas have, and the authors argue it stopped growing because it has a second job. Pandas walk flat footed, with the palm on the ground, so the radial sesamoid also carries body weight with every step. A bone that has to bear weight while walking cannot grow into a long, freely moving digit. Wang and colleagues suggest that balance between feeding and walking is probably the main reason the false thumb never evolved into a full finger.

Red pandas have one too

Red pandas also have an enlarged radial sesamoid, and they use it to grasp bamboo as well. For a long time that looked like strong evidence that the two pandas were close relatives. They are not; see are red pandas related to giant pandas?

Fossils helped explain the match. In 2006, Salesa and colleagues reported in PNAS on bones of Simocyon batalleri, an extinct, puma sized relative of the red panda from the Batallones site near Madrid, Spain. It had a false thumb too, very like the red panda's, even though it was a partly tree dwelling meat eater rather than a bamboo specialist. The authors concluded that the red panda's false thumb was probably inherited from an early member of its family, and likely evolved first as an aid to climbing. The giant panda's, by contrast, probably evolved for handling bamboo. Two unrelated animals arriving at the same solution is what biologists call convergent evolution, and the authors describe the pandas' thumbs as one of the most dramatic cases of it among vertebrates.

What the false thumb lets a panda do

• Hold stems while eating. A panda sits upright, grips a stem against the false thumb, and bites or strips the leaves.
• Handle small objects. Endo and colleagues found the double pincer lets pandas manipulate objects with great dexterity, not just thick stems.
• Still walk normally. Because the bone also carries weight, the same paw works on the ground and at the table.

To learn more about how giant pandas live on such a tough diet, read our panda diet guide and the giant panda profile, or compare both species in our giant panda vs red panda guide.