Panda thumb and taste for bamboo evolved twice

Apart from their shared moniker and adorable appearance, the red panda and giant panda don’t appear to have a whole lot in common.

This isn’t surprising, given the two species aren’t closely related – their family tree diverged 43 million years ago. But a new study, published in the Proceedings of the National Academy of Sciences, has identified genetic information that could contribute to the development of “false thumbs” in both animals, as well as their predilection towards bamboo.

The development of similar traits across distinct species is known as convergent evolution. A team led by Yibo Hu, Qi Wu, Shuai Ma and Tianxiao Ma at the Chinese Academy of Sciences in Beijing wanted to find the genetic story behind this phenomenon as it occurs across the two “panda” species.

Despite evolving quite separately, both species have ended up with under-developed thumbs which facilitate their shared bamboo diet – another unusual development, considering both species are classified as carnivores.

This makes “them ideal models for studying convergent evolution”, the researchers write.

By comparing the updated genome of the giant panda (Ailuropoda melanoleuca) with that of the red panda (Ailurus fulgens), the team saw convergence in genes involved in digestion, and in using vitamins, amino acids and fatty acids, all of which are found in bamboo.

The team also found changes to sets of genes linked to the development of arms, legs and fingers, which could contribute to the question of the false thumbs.

“Limb development genes DYNC2H1 and PCNT have undergone adaptive convergence and may be important candidate genes for pseudothumb development,” the researchers write.

The team also found 10 genes that had been downgraded to pseudogenes in both species. This included the gene that encodes receptors for umami taste – the savoury taste associated with meat.

“To survive in a novel environment, animals can drastically change their diet [with] profound impacts on species ecology, behaviour, physiology and even morphology and genetics,” the researchers explain.