West Asia - The Fertile Crescent

Climate, particularly climate change, has been very important in the development of plants and animals, particularly humans. The Earth’s climate has reeled between glacial and inter-glacial cycles for over 900,000 years. The cyclical nature of climate change has been mentioned previously. As a reminder, the last glacial period started some 115,000 years ago, reached a peak about 21,000 years ago, and ended some 11,500 years ago. The Earth’s orbit started to change 18,000 years ago, resulting in the start of our present warm period. The rapid change from the end of the last glacial to the present has been compounded by additional mechanisms such as salt gradients in the oceans. The melting of the ice caps released large quantities of water that was picked up by the dry winds causing a worldwide increase in rainfall. This removal of water by evaporation caused the water at the Arctic to become saltier and denser, so it sank to the ocean depths dragging warmer water from south to make up. This increased the conveyor of equatorial heat to the Arctic raising the sea and air temperatures and causing further melting of the ice.

However the transition to a warmer environment was far from the gradual change imagined, and the intensity of change varied round the world. There were some very rapid temperature cycles that had dramatic effects on regional climate and the availability of food. In the Middle East and Europe, for example, man had become a very effective hunter of larger animals such as mammoth and bison, but the rapid change to warmer and wetter weather, possibly helped by over-hunting, caused them to first move further north and then die out some 10,000 years ago.

Analysis of the ice cores from Greenland showed that temperatures there increased by 7 degrees centigrade over a period of only 50 years! It was a stupendous task for both plants and animals to adjust to and survive such rapid changes, and many did not. The magnitude of these temperature changes were far worse than the present projections causing us fears over our climate change, but the irreversible consequences do justify our current concerns. Adaptability was the secret to survival, and humans adapted by moving to areas with greater food sources, changing diet, hunting smaller animals and learning more about the behaviour of plants and trees – the precursor to agriculture.