Fossils of a panda ancestor have been discovered in Yunnan Province, southwest China.

About six million years old, these bones have enabled researchers to solve the mystery around the "sixth thumb" of this animal.

Among the fossils is indeed a particularly large wrist bone, called the radial sesamoid.

This is the oldest evidence for the existence of a "sixth finger" in the giant panda, which allows it to grasp and break thick bamboo stalks, the researchers explained in their study, published on 30 June in the journal

Scientific Reports


A @SciReports paper presents the earliest fossil evidence of a thumb-like sixth digit used by giant pandas and their ancestors to grip bamboo.

The findings indicate that the panda's dedicated bamboo diet may have originated at least 6 million years ago.

— Nature Portfolio (@NaturePortfolio) July 4, 2022

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Lighting on a mysterious “false thumb”

This fossil belongs to an ancestor of the panda, the


, which lived in China between six and eight million years ago.

“The giant panda is a rare case of a large carnivore turned herbivore,” says Wang Xiaoming, curator of paleontology in Los Angeles.

"The Ailurarctos

'false thumb'

shows [...] for the first time the probable timeline and evolutionary stages of bamboo feeding in pandas.


The existence of the "false thumb" had already been known to researchers for almost a century.

But this fossil evidence sheds light on several questions that have long gone unanswered, including how and when this extra toe, which does not exist in any other bear, evolved.

Millions of years ago, pandas swapped their protein-rich, omnivorous diet for the nutrient-poor, year-round bamboo in southern China.

They eat up to fifteen hours a day, and an adult panda can consume 45 kg of bamboo daily.

Giant pandas also occasionally hunt small birds.


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  • Panda

  • China

  • Paleontology

  • Animals

  • Science