Monday, 19 March 2012
choice quality stuff
The remark may say something about the efficiency of committees, but the suggestion that the camel is somehow an example of poor design is ridiculous. If we take the design brief to be for a large quadruped to live in arid and semi-arid regions of the world, where the going underfoot is often loose and unstable, where forage is often sparse and thorny, where water sources are few and far between, and where temperature ranges are among the most extreme on the planet, then it is the horse that is poorly adapted to survive.
Given such an extreme environment, we must expect the design solution to be extreme too, and so it is. The camel’s large splayed feet resolve the difficulty of walking on loose, shifting sands; its long spindly legs and knobbly knees, compared with those of a horse, keep its body further away from the heat being radiated by the ground beneath it and themselves absorb little heat; and its thick coat provides insulation against that heat. Its leathery lips and mouth are well suited to browsing the type of thorny vegetation that is typically found in deserts and rangelands, and its hump(s), which are composed mainly of fatty tissue, provide a great food reservoir that can be replenished from time to time when greener food is available.
The camel’s internal design is also conditioned by its external environment and the need to conserve water: it is able to drink, at one time, much more water than other animals (typically 100–150 litres) without suffering toxic effects, because its red blood cells can withstand greater changes in osmotic pressure without rupturing. Individual red blood cells are ovoid rather than spherical, an adaptation common in birds and reptiles but not found in any other mammal, so it can maintain blood flow more easily when in a dehydrated state.
The camel can also withstand changes in body temperature that would kill most other mammals, typically ranging from 34°C at night up to 41°C during the day. Only above the higher threshold does it begin to sweat, and evaporation of the sweat takes place on the skin surface, which provides more efficient cooling for a given amount of water lost than if the evaporation were to take place on the surface of the animal’s coat. A camel can also survive a loss of up to 25 percent of its body weight as a result of dehydration, whereas other animals would be likely to suffer cardiac arrest with a weight loss of 15 percent.
Other features that help to conserve water include nostrils that trap a high percentage of the water vapour in exhaled air, urine that is so concentrated that it comes out as a thick syrup, and faeces so dry that they can be used as fuel almost immediately (cow dung has to be dried first). Dust and sandstorms are a perennial feature of desert landscapes, but the camel has this covered too: it can close its nostrils at will, and its long eyelashes keep out blown dust and sand very effectively.
How well the camel is suited to a harsh arid environment can be judged by an unwitting experiment carried out in the late nineteenth century, when dromedaries (the ones with a single hump) were introduced to Australia as beasts of burden. The current estimated population of feral camels in the Australian Outback, all descended from these original importees, is now about one million, and it is believed to be increasing by 8 percent per year. That other imported beast, the sheep, is unable to compete.
Consequently, if you are tempted to repeat Issigonis’ vapid aphorism in the belief that you are somehow demonstrating your cleverness, you just might want to reflect on the knowledge that the camel has been domesticated at least as long as the horse, and that the nomads who did this clearly had a better insight into the virtues of this remarkable creature than you do. The only reasonable thing that one can say that connects a camel to a committee is that a committee would probably struggle to design one that worked.