The exclusive bamboo food bears giant panda began six million years ago, according to a new study fossil-based fake thumb that these animals and their ancestors used to manipulate said plant. The conclusions of the study, conducted by the paleontologist Xiaoming Wangwere published in Scientific reports.
This bamboo lover’s hand never developed a true opposable thumb in its evolutionary history, but rather a similar digit from a wrist bone, the radial sesamoid. Studies previous They had already documented the existence of this structure between 100 and 150 thousand years ago. However, it was possible to estimate for the first time from when the species began to feed only on bamboo.
It was possible to estimate for the first time from when this bear from China began to feed only on bamboo: six million years ago
“This food is available all year round and is plentiful enough that the pandas don’t have to go too far to find food. This availability is an advantage even if bamboo is poor in nutrients. It is an evolutionary trade-off to sacrifice a richer diet in exchange for more passive hunting, compared to that of their ancestors,” Wang told SINC.
A possible common evolutionary line
Wang’s team examined the wrist bone of an ancestor of the panda, the Ailurarctos, disappeared 8 million years ago and discovered in Shuitangba, China. They compared the fossil with the shape and thumb size of modern specimens: the giant (Ailuropoda melanoleuca) and red (Ailurus splendens). In the analysis, traces of indarctoid arctoida bear that lived nine million years ago and may have the same ancestor.
The researchers determined that the thumb of the modern panda was the same shape as the wrist bone of Ailurarctos, but not that of I. arctoides, which was taller, broader and hooked.
Although the thumb-shaped sixth digit was not present in the ancient bear or the common ancestor it shares with pandas, it has long been present in the lineage of black and white bears.
This fact indicates that although the thumb-shaped sixth digit was not present in the ancient bear or in the common ancestor it shares with pandas, it was present in black and white bear lineage for at least six million years.
Placement of the panda’s false thumb (white bone in the image) when grabbing the bamboo and when walking. / Los Angeles Museum of Natural History
Differences from the ancestor of the panda
Also, the researchers observed differences in size and shape between the false thumb of modern giant pandas and that of the Ailurarctos. The former is significantly shorter than that of its ancestor relative to its body size, and has a hook at its end and a flattened outer surface.
The authors propose that the hook may help modern specimens grip bamboo better, while the shorter length and flattened outer surface help distribute weight when walking. These load limits they could be the main reason why the giant panda’s thumb-like structure never evolved into a full figure, they add.
The authors propose that the hook may help modern specimens grip bamboo better, while the shorter length and flattened outer surface help distribute weight when walking.
“Five or six million years should be enough for the panda to develop longer false thumbs, but it seems that evolutionary pressure to travel and bear weight has made it short enough to be useful, without being tall enough to stand on its own. get in the way,” says Denise Su, one of the study’s authors from the University of Arizona.
“I’d love to answer all kinds of questions about the ancestors of these animals, but because of a lack of suitable fossils, I’m often unable to answer them. It would be nice, for example, to find the rest of the bones (not just the thumb) and to know the skull and jaws,” Wang concludes.
Reference:
Wang, X., Su, DF, Jablonski, NG et al. The giant panda’s first false thumb suggests conflicting demands for locomotion and feeding. Scientific representative 12, 10538 (2022). https://doi.org/10.1038/s41598-022-13402-y
Source: SINC
Rights: Creative Commons.