The giant panda has been considered one of the oddest of zoological specimens. Its anatomy suggests it belongs to the carnivorous mammals such as dogs, bears, raccoons, cats and seals, yet it subsists primarily on a diet of bamboo. Most experts believe that the herbivorous panda is descended from a meat-eating bear that evolved to eat plants – but this was based largely on conjecture.
Now the hypothesis can be tested in another way by analysing the panda's genes. A huge team of largely Chinese scientists have sequenced something like 94 per cent of the panda's genome and have concluded, among other things, that its bamboo diet might be more dependent on the bacteria that lives in its gut than on the type of genes it possesses.
The repertoire of genes that make up the panda's genome do indeed look rather like those of a typical carnivore. However, there is one notable exception. The gene responsible for the umami taste receptor – the ability to taste animal protein – is evidently defective when scientists looked at its genetic sequence, published in the journal Nature.
In this respect, the panda's genetic make-up reflects its abandonment of meat in favour of a bamboo diet because there was simply no need to continue to be able to detect the taste of animal protein. Like many animals that abandon a particular way of life, the panda has lost those adaptations that had specifically evolved for that modus operandi.
Stephen Jay Gould famously highlighted another feature of the panda that had evolved as a result of its transition to a bamboo diet. The panda's opposable "thumb", which is not actually a thumb but a bony extension of the sesamoid bone in its paw, helps the animal to strip the edible leaves from a bamboo cane. Gould used the example of the panda's thumb to show that evolution has to make do with what it has got in terms of existing anatomy – poor design is a better argument for evolution than good design.
It goes to show that every animal's genome has a story to tell. Especially the poor endangered panda, which has become such an icon for conservationists around the world.
A load of hot air
I had one of them climate sceptics in the back of me car the other day, berating me about how the science of global warming was crumbling away like a Himalayan glacier. Figuring that this was going to be a recurring theme I thought of a 30-second riposte.
Look at the facts. We know that carbon dioxide concentrations in the atmosphere are rising. We know that burning fossil fuels is adding to the CO2 concentration in the air, and we know that carbon dioxide is a major greenhouse gas – not even the most fervent sceptic would disagree with those facts.
We can estimate from the established physics how much extra warming is occurring as a result of the above. If this extra warming is being added to the global climate system then where is this heat going if it is not warming up the Earth? Answers on a postcard please.