Sheer weight of numbers

Try thinking quantitatively about the hold humans have on the world. There are about 400,000 African and 40,000 Asian elephants. At about seven tonnes apiece, this means that the world has 3-4 million tonnes of elephant. This is about 1 percent of the mass of humans.

Throughout history, human beings have been reluctant to share their environment with any other large undomesticated animal. Maybe they are dangerous, perhaps they compete with us for space and food, or maybe they just disturb our idea of our own importance. The best place to find them now is in the oceans – hence the popularity of whale watching – and in game reserves in Africa. There is certainly no large wild land animal that exists in numbers remotely comparable to the billions of humans. The most successful mammals, judged by numbers, are the farm animals that humans keep, or species such as rats that have learnt how to make the most of our growing numbers.

Before we get too pleased with our success, however, we should remember that there are estimated to be 1 quadrillion ants in the world – that's 1 followed by 15 zeroes – with a total weight about the same as that of humans.