Many people think that pandas have six fingers. In fact, this "sixth finger" that came out in the historical evolution is not a real finger, but an enlarged wrist sesamoid, which is also known as the "pseudo-thumb". In other words, the sixth finger is incorrect. The panda's hand index is actually five.

This wrist sesamoid bone is called "bone", but it is actually a meat pad without bones. This meat pad can't grow nails, but it is as flexible as a thumb. It can hold the five fingers of the panda's forefoot (the real five fingers can't bend or be flexible).

This kind of grasping skill is not common in animals. Except koalas, North American opossums (toes) and most primates, they also eat bamboo pandas. Only the giant panda and the red panda have developed a "sixth finger" to hold the other five fingers, which is indeed an evolutionary optimization.

Extended data:

The reason of animal evolution is determined by survival and life. The giant panda's extra "sixth finger" is to get and hold its food-bamboo more flexibly and conveniently.

In fact, the earliest giant pandas ate meat, and their digestive system was also a typical carnivorous animal structure. Although bamboo is not as nutritious and delicious as meat, it is widely distributed and abundant, and other animals don't eat it. Hiding in bamboo forests can also avoid large animals such as saber-toothed tigers.

This great change in feeding methods has greatly helped pandas to reduce direct competition with other species and get enough food, which is a wise move.

Moreover, according to the research, due to gene mutation (Tas 1r 1 pseudogeneization), the panda lost its umami receptor 4.2 million years ago, which means that the taste of the meat in the panda's mouth may not be better than that of the fragrant bamboo. In order to eat bamboo, how long is a "finger"? This is the secret of the panda's "six fingers".

Baidu Encyclopedia: Giant Panda (Mammal)