Ten years ago I read a review of a book, which I just had to have, and I bought it. It was by Steven Mithen (After the Ice: a global human history, 20,000-5000 BC), and I read it from cover to cover, greedily. It told the story of the development of humanity from 20,000 years ago, and used prehistoric and anthropological evidence in an imaginative and attractive way. I had wondered for years whether or not there had been an earlier human civilisation between earlier ice ages. Mithen thinks not, and he is joined by all the experts I have talked with. What you see in our present civilisation is the result of the work of several hundred generations of human beings. What we have done — our species — has no counterpart in the history of the planet.
Then, a month ago, I read a long article on Watts Up With That by Andy May, a physicist interested in rocks, on the same subject, and he relied on and acknowledged his debt to the same book. To better explain his own argument May created a giant chart. It is packed with information, drawn from good sources, and it looks like this:
No, I agree that you can’t read the text. To do that you’ll have to go the article at the link above, and it is very well worth doing — that is, if this sort of thing interests you. But some of what is there will be clear as I try to summarise what is a very big picture indeed. The timelines move from the left to the right, and the three long lines in the upper half are temperatures in Greenland and Antarctica over the last twenty thousand years, based on ice-cores. You can see that the last ten thousand years they have been steady, with small fluctuations above and below the mean.
One of May’s continuing themes is that, for all life, cold is bad and warm is good. Civilisations collapse when there is prevailing cold, which tends to bring with it drought. Warm times tend to be wet times, and plants flourish. So too do we humans. The last glacial period can’t have been very enjoyable, and humanity cannot have been a dominant life form. But something happened around 13,000 years ago, with the beginnings of urban life, cut short very quickly by what is called ‘the Younger Dryas’, a return to glacial cold that lasted for a thousand years.
When it ended there was a further burst of agriculture and urban development, with domesticated animals and large-scale farming. The modern city of Jericho seems to have occupied a site of urban life for 11,600 years. The Sahara became savannah-like. Around 8000 years ago there was another long-term cold snap, which returned the Sahara to desert-like conditions, and ended many settlements, with survivors moving to permanently flowing rivers, like the Nile. From then on we have quite a lot of archaeological evidence, and then from five thousand years ago, we have written or engraved evidence.
The warm and cold periods in the last ten thousand years can be determined quite accurately through ice-core data, and they accord with what we know of the rise and fall of human civilisations. All of this was in a sense known to me because I was trained in history, though I knew nothing of the ice-core evidence. But human history is my intellectual base, and I have known for a long time that the decline and fall of the Roman Empire was associated with a change in climate, with cold in the North of Europe pushing more and more tribal groups south, where crops could still be grown. That put enormous pressure on the Roman frontiers, and they simply gave way.
The return of human urban civilisation from the ‘Dark Ages’ to the Renaissance from which we date modern civilisation, is likewise associated with the return of warmth to Europe. We know about the Little Ice Age (which was not a consistently cold period, but a generally cooler one with some notably frozen short episodes) because there is abundant literary, historical and pictorial evidence of it.
I accept that natural scientists might not have learned any of this in their own education. But that all this could simply have been ignored, when the IPCC began to look at global warming, almost passes belief. While I have given May’s long essay scant treatment here, it is really worth a good read, and the chart is a great piece of work.