The exclusive bamboo-based diet of giant panda bears began six million years ago, according to a new study focused on fossils fake thumb that these animals and their ancestors used to manipulate said plant. The conclusions of the study, led by paleontologist Xiaoming Wanghave been published in ScientificReports.
The hand of this bamboo lover has 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. Now, it has been possible to estimate for the first time from what moment the species began to feed only on bamboo.
“This food is available throughout the year and is plentiful enough that the pandas don’t have to go too far to find food. This availability is an advantage even though bamboo is low in nutrition. It’s an evolutionary trade-off to sacrifice a richer diet for more passive hunting, compared to their ancestors.”explains Wang to SINC.
A possible common evolutionary line
Wang’s team examined the wrist bone of an ancestor of the panda, the ailurctos, disappeared 8 million years ago and discovered in Shuitangba, China. They compared the fossil with the shape and size of the thumbs of modern specimens: the giant (Ailuropoda melanoleuca) and red (Ailurus fulgens). In the analysis, traces of the arctoid indarctoida bear that lived nine million years ago and may have the same ancestor.
The researchers determined that the modern panda’s thumb is the same shape as the human wrist bone. ailurctosbut not the I. arctoides, which was larger, wider and hooked. 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 has been present in the lineage of the black and white bear for at least six million years.
Differences with 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’s is significantly shorter than its ancestor’s 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 better grasp the bamboo, while the shorter length and flattened outer surface facilitate weight distribution when walking. These load bearing limitations they could be the main reason why the giant panda’s thumb-like structure never evolved into a full digit, they add.
“Five or six million years should be enough for the panda to develop longer false thumbs, but it seems that the evolutionary pressure of traveling and supporting its weight made it short enough to be useful, without being big enough. to hinder”points out Denise Su, one of the authors of the study from the University of Arizona.
“I would like to answer all kinds of questions about the ancestors of these animals, but lacking appropriate fossils, I am often unable to address 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.
Font: Edgar Hans Cano / SINC Agency
Reference article: https://www.agenciasinc.es/Noticias/Los-pandas-evolucionaron-seis-millones-de-años-ago-para-incorporar-el-bamboo-a-su-dieta
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