Climate as a Determining Feature of Civilization

It is notable that over the last six thousand years many great civilizations have arisen, enjoyed a few centuries of power, and then faded into insignificance. Why has this happened when and where it did?

There are many conditions necessary for the rise of a civilization. The land area must be large enough to support at least a few hundred thousand people. The land must be fertile enough to support a range of edible crops, and there must be available animals that can be domesticated and are strong enough to carry burdens, including man himself (Diamond 1999).

In addition, the climate must be suited to man himself, not so hot and humid that he becomes lazy and listless, especially if there is plenty of fruit for the picking. On the other hand it must not be so cold that all his energies are concentrated on survival. Extensive studies have shown that man survives best at a temperature between 60 and 70 degrees F, with moderate humidity. He feels well, and is active and energetic. Below about 60 degrees it is too cold, but somewhat above 70 is quite tolerable. We might therefore expect the earliest civilizations to arise around the 70 degrees isotherm, and indeed this is the case. The isotherm passes through North Africa, Egypt, Mesopotamia and the Indus valley, all sites of early civilizations (Markham 1947).

Subsequently, improvements in technology enabled people to survive in cooler regions. They learned to make clothing to keep them warm and to build houses to retain the heat. Glass was invented and made windows possible. The Romans invented the hypercaust that enabled them to keep their homes warm in cold weather. Civilization then spread northwards with the help of Roman technology. Around the end of the first millennium AD improvements in agriculture further aided the spread of civilization. The stirrup and the horse collar enabled the horse to replace oxen for ploughing, and together with the wheeled plough that turned the soil over enabled the heavy fertile soils of Northern Europe to be opened up for cultivation. This in turn enabled the land to support a much greater population than ever before.

Further support for the influence of climate comes from the experiences of people who emigrate from a temperate climate to one that is hot and humid. The first generation survives well, but subsequent generations become less active and listless, leading eventually to the 'poor white' people living permanently in countries like the Bahamas and South Africa. Such people can sink lower than the much more primitive indigenous populations. This decline can be avoided if the emigrants take periods of leave to spend time in their home countries, as was the practice of many people who went to tropical climates such as India and the Far East.

Now, with heaters in the winter and air conditioning in the summer, we are able to survive and work in more extreme conditions and so the enervating effects of an unfavourable climate are not so pronounced, and may be eliminated entirely. Our global civilization has spread over most of the earth apart from the very cold regions around the poles and the deserts of Africa and Central Asia. We have largely become divorced from the natural processes on which ultimately we depend. We are not so conscious of the seasons, as we enjoy continuous supplies of fruits and vegetables from all over the world. If, however, some catastrophic climate change occurred, coupled with destructive storms and tidal waves, it might not be possible to rebuild the infrastructure that enables us to prosper in somewhat unfavourable climates.

We would do well to remember that our civilization depends on adequate supplies of energy and we are still at the mercy of earthquakes, tornadoes, tsunamis and volcanic eruptions. We still rely on nature to provide our food, and this in turn depends on the climate. If the climate changes, it may become more difficult to grow the crops we need, and our domestic animals may suffer. If the increasing demand for more energy is met by burning fossil fuels the resulting pollution will reduce the productivity of the land and the sea. At the same time the world population inexorably increases and the demand for a higher standard of living will be difficult if not impossible to meet.

These problems are inextricably linked together. The rising population and its rising expectations require more energy. The production of this energy is made increasingly difficult as the reserves of possible fuels are exhausted. Energy production can cause global warming and climate change, and this reduces the capacity of the earth to grow the needed food. In the end, something has to give way. Will it be famine, or wars or pestilence, or a combination of the three?

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