A recent “big discovery” about bears, published this week, may be of interest to you. Two BSG members are authors: Fuwen Wei (Chinese Academy of Sciences) and Zejun Zhang (China West Normal University).
Their article indicates that giant pandas had a more diverse diet, just 5,000 years ago. The authors compared stable isotopes in bone and teeth of present day pandas with ancient pandas, and noticed a much larger spread in the ancient ones, indicating that their diet was not restricted to bamboo: https://www.cell.com/current-biology/fulltext/S0960-9822(19)30004-1 What struck me is how the panda’s special adaptations to feeding on bamboo, notably the very large jaw muscles and especially the “false thumb”, could have evolved so quickly.
One possibility is that their false thumb – an extension of one of the wrist bones – was already well developed in ancient pandas, even though bamboo was not their only food. For example, this bone is extended in Andean bears, compared to the Ursine bears, possibly enabling them to better manipulate bromeliads. It is also enlarged in the extinct Indarctos bears (a genus that spread across N. America, Europe, North Africa, and Asia, which died out about 5 million years ago).
Of note, this same bone is enlarged in red pandas, which also eat bamboo, but their diet is broader than giant pandas. Some morphologists believe that this adaptation in red pandas initially evolved to aid in their grasping abilities when climbing out on small tree limbs. There is an extinct puma-sized carnivore found in Spain that possessed a “false thumb” – it was arboreal and didn’t eat bamboo. Notably, the oldest fossil ancestor of the giant panda is also from Spain – but the coincidence ends there. The giant panda lineage is not very arboreal, so their false thumb must have developed for feeding. But what they fed on before bamboo, that needed the assistance of an opposable digit, would be a mystery.
This doesn’t have much to do with conservation, except to highlight how different the giant panda may have been in the past. It is often viewed as a species locked into a single type of food, and reliant on old-growth forest. But in terms of conservation, it is revealing that pandas are now expanding their range, using higher elevations and more diverse habitats of successional forests. This is shown in another recent paper authored by 4 BSG members (Ron Swaisgood, Megan Owen, Xiaodong Gu, Zejun Zhang), based on a unique analysis of data from 2 rangewide surveys: https://onlinelibrary.wiley.com/doi/pdf/10.1111/conl.12575 Things to think about.
Things to think about. Enjoy, Dave