Sheng Yi, a female panda, forages on bamboo leaves inside the panda enclosure at the National Zoo in Kuala Lumpur on May 25, 2022. AFP
叠贰滨闯滨狈骋鈥�The discovery of panda fossils in China has helped researchers solve the mystery of how the giant species developed a 鈥渇alse thumb鈥� and became the only dedicated vegetarian in the bear family.
Fossils dating back about six million years found in southwest China鈥檚 Yunnan province included a greatly enlarged wrist bone called a radial sesamoid.
It is the oldest known evidence of the modern giant panda鈥檚 false thumb that allows it to grip and break heavy bamboo stems, scientists wrote on a research paper published in the latest edition of the Scientific Reports.
The fossils belong to the now-extinct ancient relative of the panda called an Ailurarcto that lived in China six to eight million years ago.
鈥淭he giant panda is鈥� a rare case of a large carnivore with a short, carnivorous digestive tract鈥� that has become a dedicated herbivore,鈥� Wang Xiaoming, curator of vertebrate palaeontology at the Natural History Museum of Los Angeles County, said.
鈥淭he false thumb in Ailurarctos shows鈥� for the first time, the likely timing and steps in the evolution of bamboo feeding in pandas.鈥�
Researchers had known about the panda鈥檚 false thumb, which works similar to a human thumb, for about a century. But the lack of fossil evidence had left unanswered questions about how and when the extra digit 鈥� not seen in any other bear 鈥� evolved.
鈥淲hile the giant panda鈥檚 false thumb is not the most elegant or dexterous鈥� even a small, protruding lump at the wrist can be a modest help in preventing bamboo from slipping off bent fingers,鈥� Wang wrote.
The fossils found near Zhaotong city in the north of Yunnan included a false thumb that was longer than that found in modern pandas, but without an inward hook on the end.
The hook and a fleshy pad around the based of the thumb evolved over time since it had to 鈥渂ear the burden of considerable body weight鈥�, the paper said.
Pandas traded the high-protein, omnivorous diet of their ancestors for bamboo, that is low in nutrients available year-round in South China millions of years ago.
They eat for up to 15 hours a day and an adult panda can consume 45kg of bamboo a day. While their diet is mostly vegetarian, wild panda are known to occasionally hunt small animals.
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