A bear that wandered what is now China about six million years ago is the oldest bamboo-eating panda ancestor yet found-and it had the same short and fat false thumbs that stick from the wrists of today’s pandas alongside their five fingers. Fossils(化石) of the new species suggest such “thumbs,” which helped the animals eat bamboo, maintained their peculiar shape to facilitate the beast’s four-legged movement.

The fossils, found in the province of Yunnan and described in Scientific Reports, also push back the date that pandas’ ancestors likely changed from eating meat to chewing bamboo-from two million to six million years ago. “Giving up on a meat-eating diet means trading the unstable life of a meat-eater for quiet consumption of the plentiful bamboo,” says paleontologist and study lead author Xiaoming Wang of the Natural History Museum of Los Angeles, adding that it was “not a bad deal.”

Although the fossils dug from the province’s Zhaotong Basin included only teeth and some limb(肢) bones from the bear, these were typical enough for Wang and his colleagues to identify the fossils as belonging to an early member of the panda lineage called Ailurarctos. A wrist bone in the collection, with its proto-thumb, stands out among the remains. “Its structure is really close to that of the living panda,” says Juan Abella Pérez of Miquel Crusafont Catalan Institute of Paleontology in Barcelona, who was not involved in the new study.

Why didn’t this short and fat thumb evolve into a longer, larger false thumb to better grasp a meal? The researchers propose that walking on all fours was the key reason. If the panda’s thumb were larger, Wang and his colleagues suggest, the appendage(附属物) could have affected its walking or faced a high risk of breaking. In a sense, this makes the evolution of the panda’s thumb all the more impressive. The structure was limited by the need to move as well as to eat.

【小题1】What inspired the scientists’ research?

A．Pandas.	B．Bears.
C．Fossils.	D．Bamboos.

【小题2】Why did pandas’ ancestors turn to bamboos?

A．Bamboo tasted better.

B．They found bamboo sufficient.

C．They knew it was a good deal.

D．They were tired of eating meat.

【小题3】What does Juan think of the finding?

A．It’s convincing.

B．It matters little.

C．It’s misleading.

D．It remains to be tested.

【小题4】What is the passage mainly about?

A．Where pandas’ ancestors lived.

B．What contributed to pandas’ movement.

C．How pandas’ ancestors began to eat bamboo.

D．Why pandas’ ancestors possessed such thumbs.