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Giraffe, By Edgar Williams

At the start of this appropriately elegant monograph, Williams reveals the giraffe's enviable control over its blood pressure.

The creature can contract blood vessels in its brain when lowering its head in order to circumvent celebral haemorrhage. Thick skin in the legs acts like a pressure stocking to prevent oedema. Despite being able to run as fast as a horse, it breathes nine times a minute.

We know all this, but Williams admits "how the giraffe got its long neck is still unknown". Doubt has been cast on Darwin's theory that it enabled them to "reach food beyond the reach of other animals". Why did no other herbivore develop a long neck? Like us, the giraffe has seven neck vertebrae. Once common in Africa, the giraffe now depends on humanity for survival.