Monday, 19 November 2012

On The Origins Of Giant Pandas

The giant panda (Ailuropoda melanoleuca)
Giant pandas (Ailuropoda melanoleuca) are one of the most recognizable mammals on the planet. At almost 2 metres tall and weighing up to 60 kilograms with their distinctive black rings of fur around their eyes the giant panda, contrary to popular belief, is carnivorous. While their diet consists primarily of bamboo, they will feed on birds, rodents and carrion. Today their geographical range is restricted to a few select areas of Asia.

A genetic study of the giant panda genome suggests that they evolved around 18 to 22 million years ago. The eminent biochemist Nick Lane states in his fantastic book Life Ascending that fossils are a 'beautiful distraction,' a part of an incomplete record of the Earth's evolutionary past, which draws attention away from genetic studies which can provide exact answers to the origins of various animal groups.

What DNA cannot provide, however, is where these creatures came from. Genetics can tell us that the giant panda lineage split away from the rest of the mammal lineage around 18 to 22 million years ago. It does not reveal the fact that its ancestors lived in Spain; tens of thousands of kilometres away from its known Asian stronghold.

The 11.6 million year old skeletal elements of Kretzoiarctos beatrix
Earlier this year, two sets of jaws and teeth from ancient giant pandas were found in north-east Spain in 11.6 million year old rocks. Smaller in size than its modern day equivalent, the giant panda was more or less the same size as the sun bear, the smallest species of bear on Earth. The environment in which it lived was near tropical and so it would have had a wide range of food sources available to it, yet its teeth showed the distinctive signs of wear and tear resulting from a diet of tough, fibrous foodstuffs.

In the end, the species was given the name of Kretzoiarctos beatrix, in honor of two scientists; Miklos Kretzoi who named several other species of extinct panda; and Beatrice Azanza, a colleague of the research team who uncovered the fossils. Yet a nagging question is why exactly did Kretzoiarctos become extinct? 11.6 million years ago, Spain was a near tropical country. Today, the country is rather drier and hotter. It is possible that Kretzoiarctos went extinct simply due to climate change and a lack of vital plant-food. Yet evidence is scant.

The modern panda faces different challenges: the destruction of its natural forest habitats and poaching. The bones and teeth are used as ingredients in traditional Chinese medicine. This has placed the giant panda high into the endangered species list. If attitudes don't change, we will be responsible for the death of a lineage stretching back at least 18 million years, over 100 times older than our own.