How long have pandas been eating bamboo? At least 6 million years, study suggests
- Fossils unearthed in southwestern China show panda ancestors had ‘false thumb’ for grabbing food
- Researchers say the bears’ sixth digit never fully developed because it would have impeded walking ability
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The researchers found that the bone has stayed the same size since the late Miocene period and never evolved into a fully developed thumb.
When pandas walk, the bottoms of their paws touch the ground. If the sixth digit had grown longer, it would have compromised the bone’s dual functions – grasping and weight-bearing – and interfered with walking long distances.
“Pandas never evolved sufficiently long false thumbs to seize large bundles of bamboo, a task that, while desirable, is not critical for survival,” the researchers said, pointing to the abundance of bamboo in their habitat.
The team said it was “likely that a tight grip is more critical to the panda’s feeding ability than the volume of their grasp”, because pandas needed a strong grip to counter their powerful jaws as they eat the thick, woody grass.
“While the giant panda’s false thumb is not the most elegant or dexterous, the persistence of this distinctive morphology for the last 6 million years suggests that it has fulfilled an essential function for survival of the lineage,” they said.
The team was led by Xiaoming Wang of the Natural History Museum of Los Angeles County and includes researchers from Arizona State University, Pennsylvania State University, Harvard University, as well as the Institute of Vertebrate Palaeontology and Paleoanthropology and Kunming Institute of Zoology – both under the Chinese Academy of Sciences.
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Giant pandas spend around 15 hours a day eating up to 45kg (99lbs) of bamboo. They traded the high-protein, omnivorous diet of their ursid ancestors for bamboo – a high-fibre food with little nutritional value but year-round availability in South China and Southeast Asia, according to the researchers.
“With 99 per cent of their food being bamboo and without major competitors for this abundant food resource, nor the need to avoid predators, pandas can thus reduce daily foraging range to within tens of metres of their resting dens, permitting a highly efficient foraging strategy of spending large portions of daily activities feeding and resting within small areas,” they said.