The ancestors of giant pandas are carnivores. How can they turn from carnivores to vegetarians?

The ancestors of giant pandas are carnivores. How can they turn from carnivores to vegetarians? This is related to changes in its living environment.After the glacial attack, the giant pandas that remain in Sichuan and Gansu provinces can only survive if they gradually change their diet.As a result of long-term adaptation to the environment, giant pandas changed from carnivores to bamboo.The panda's molars have also become particularly large, suitable for grinding bamboo fibers.Pandas love to drink water because they need to digest a lot of fiber and lignin every day.Giant pandas spend 14 hours a day eating and eating about 12.5 kilograms of bamboo leaves and bamboo shoots, but only about 17% of them are digested.In fact, giant pandas do not like to eat meat, but lack the opportunity to eat meat.Because there are very few large carnivores in the distribution area of giant pandas, there are not many remains left for it to eat.If a panda catches a small animal such as a rodent, the nutrients it receives are often insufficient to compensate for the energy consumed.The giant panda is obviously a carnivorous animal, so chooses to eat bamboo.