Pandas evolved six million years ago to incorporate bamboo into their diet.

O exclusive bamboo-based diet of giant panda bears began six million years ago, according to a new studying focused on fossils fake thumb that these animals and their ancestors manipulated said plant. The findings of the study, led by 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 finger similar to 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 was possible to estimate for the first time when the species started to feed only on bamboo.

“This food is available year-round and is plentiful enough that pandas don’t have to travel far to find food. This availability is an advantage, even though bamboo is poor in nutrition. It is an evolutionary trade-off to sacrifice a richer diet in exchange for more passive hunting compared to their ancestors,” Wang explains to SINC.

A possible common evolutionary line

Wang’s team examined the wrist bone of a panda ancestor, the ailurctos, disappeared 8 million years ago and was discovered in Shuitangba, China. They compared the fossil to the shape and size of the thumbs of modern specimens: the giant (Ailuropoda melanoleuca) it’s red (Ailurus fulgens). In the analysis, traces of arcoid 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 wrist bone of Ailurctos, but not that of I. arctoides, which was larger, wider and hook-shaped.

This fact indicates that although the sixth thumb-shaped finger was not present in the ancient bear or in the common ancestor it shares with pandas, it was present in the lineage of the black and white bear for at least six million years.

Read Also:  Path to Abundance

Placement of the panda’s false thumb (white bone in the picture) when grabbing bamboo and walking. / Los Angeles Museum of Natural History

Differences with the ancestor of the panda

Furthermore, the researchers observed size and shape differences between the false thumb of modern giant pandas and that of the Ailuracts. The former is significantly shorter than its ancestor in terms of 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 grip bamboo, while the shorter length and flattened outer surface facilitate weight distribution when walking. Those load bearing limitations they may be the main reason 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 has made it short enough to be useful, without being big enough. ” says Denise Su, one of the study’s authors at the University of Arizona.

“I would like to answer all sorts of questions about the ancestors of these animals, but lacking appropriate fossils, I often cannot address them. It would be nice, for example, to find the rest of the bones (not just the thumb) and get to know the skull and jaws,” concludes Wang.