Giant pandas are notoriously picky eaters. They only chew bamboo and every day they spend 15 hours eating up to 45 kilos of the material.
But their ancestors, like most bears, ate a much broader diet that included meat, and the exclusive diet of modern pandas was thought to have evolved relatively recently. However, a new study has found that pandas’ particular passion for bamboo may have originated at least 6 million years ago – possibly due to the plant’s wide availability throughout the year.
To survive only on low-nutrient bamboo, modern pandas (Ailuropoda melanoleuca) have evolved a peculiar sixth finger, a kind of thumb that allows them to easily grasp bamboo stalks and pull out leaves.
“Gripping bamboo stalks tightly to crush them into bite sizes is perhaps the most crucial adaptation to consuming a prodigious amount of bamboo,” said study author Xiaoming Wang, curator of vertebrate paleontology at the County Natural History Museum. of Los Angeles in a study. declaration.
A sparse panda fossil record meant that how bears evolved this baffling feature that has long puzzled biologists wasn’t really understood. Previous research had found evidence of this thumb-like structure from around 100,000 to 150,000 years ago.
Wang and his team identified much earlier evidence of pandas with an extra finger — and thus a diet made entirely of bamboo — in the form of a fossilized digit dating back 6 to 7 million years. The fossil, unearthed in southwestern China’s Yunnan province, belonged to a panda ancestor known as Ailurctos.
The new research was published Thursday in the journal Scientific Reports.
While the giant panda’s sixth finger is not as elegant or deft as human thumbs, the persistence of this “distinctive morphology” over millions of years suggests it plays an essential role for survival, the study noted.
compromised evolution
But what was particularly intriguing to the scientists involved in the study was that this fossilized structure was longer than those of modern giant pandas, which have a shorter, hooked sixth finger.
Wang and his colleagues think the shortest sixth digit of modern pandas is an evolutionary compromise between the need to manipulate bamboo and the need to walk and carry their sturdy bodies.
“Five to six million years should be enough time for the panda to develop longer false thumbs, but it seems that the evolutionary pressure of needing to travel and support its weight has kept the ‘thumb’ short – strong enough to be useful without being big. enough to get in the way,” study co-author Denise Su, an associate professor at the School of Human Evolution and Social Change and a researcher at the Institute of Human Origins at Arizona State University, said in a statement.
Source: CNN Brasil
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