The false thumb was not present in another closely related bear that lived about 9 million years ago, the researchers said. Because of their inefficient digestive system, pandas consume large amounts to meet their nutritional needs - 26-84 pounds (12-38 kg) of bamboo while eating up to 14 hours a day. They now live primarily in temperate forests in the mountains of southwestern China, with a wild population estimated under 2,000.Ī panda's diet is 99% vegetarian, though they do sometimes eat small animals and carrion. Pandas, one of the world's eight bear species, once inhabited large swathes of Asia. The panda's false thumb is far less effective than the human thumb, but it is enough to provide the giant panda with the grasping ability to eat bamboo,' said paleontologist and study co-author Tao Deng of the Chinese Academy of Sciences in Beijing.

'One of the most important features of human beings and their primate relatives is the evolution of a thumb that can be held against other fingers for precise grasping. The false thumb lets pandas hold bamboo to eat but not rotate the food as a true thumb would allow. Until now, the oldest-known evidence of this thumb-like structure dated to fossils from about 102,000-49,000 years ago in the same panda species alive today. The researchers initially found an Ailurarctos arm bone in 2010, then discovered teeth and the false thumb in 2015, giving them a much better understanding of the animal. The panda's tight grip on bamboo acts against the jerking action of the mouth in order to quickly break food into bite-size chunks, Wang added. And therefore, we think that is the reason that the false thumb in modern pandas has become shorter, not longer,' Wang said. Think of the false thumb as being stepped on every time the panda walks. 'The hooked false thumb offers a tighter grasp of the bamboo and, at the same time, its less-protruded tip - because of the bended hook - makes it easier for the panda to walk.

The modern panda's false thumb has some advantages over the earlier version. 'It uses the false thumb as a very crude opposable thumb to grasp bamboos, sort of like our own thumbs except it is located at the wrist and is much shorter than human thumbs,' said Natural History Museum of Los Angeles County paleontologist Xiaoming Wang, lead author of the research published in the journal Scientific Reports.Īilurarctos was an evolutionary forerunner of the modern panda, smaller but with anatomical traits signaling a similar lifestyle including a bamboo diet. The false thumb serves a similar function. A bear's hand lacks the opposable thumb possessed by humans and various primates that enables the grasping and handling of objects using the fingers. The false thumb is an evolutionary adaptation to augment the existing five actual digits of the panda's hand.

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