Looking for a pre-Ice Age civilisation?
An interesting thought experiment is to consider the rise of modern civilisation and to ask whether civilisations could have risen in the long distant past. Let’s look at some graphs to see the plausibility of the climatic side of this.
Firstly we can see on this graph (source here) that there was a rapid change in temperature following the end of the last ice age. We can see that around 14,000 years ago the global temperature average was around 7 degrees colder than today and that there was very rapid warming over the past few thousand years.
From about 11,500 years ago we can start to see evidence of megaliths, temples and communal living at places like Gobekli Tepe. And then we have the rise of civilisation in Sumeria from around 7000 years ago. By looking at the graph we can see this coincides with the climate entering the green zone of warmer temperatures particularly suitable for agriculture and warm blooded homo sapiens. The Holocene is defined as this period, starting from around 11,700 years ago.
So, it’s reasonable to suggest that one of the main requirements for the growth of civilisation was this climatic change which allowed for large-scale agriculture, leading to a shift from nomadic to sedentary lifestyles. This would have then driven humans into every larger communal settlements requiring greater administrative control, thus sowing the seeds for the rise of civilisation.
The question is, when was the last time that climatic conditions were similar to our current holocene? I chose to add the green zone at 11 degrees – as this matches roughly when we see the beginnings of larger scale civilisation post ice age. Extending this line back we can see that our current climate is pretty rare – it’s only occurred on 3 occasions in the last 500,000 years and on each occasion only lasts for around 10,000 years.
If we take the start of anatomically modern humans as around 300,000 years ago, then there would only be one plausible climatic optimum – that from around 127,000 to 117,000 years ago. After this, there was a rapid cooling, followed by the Toba super volcanic eruption around 74,000 years ago and then a descent into an ice age. So, this 10,000 year window would have been the most likely time during which any earlier human civilisations would have had the best chance of success.
So, when looking at the rise of civilisation, if climate was the main driver then our question needs to be why did this not occur in this earlier period? If a lower-technology civilisation did then it would be unlikely that any evidence would survive over 100,000 years. We can say that no civilisation has previously achieved nuclear technology by studying levels of radioactive isotopes in the atmosphere, and that there has been no previous large scale fossil fuel based industry by looking at the undisturbed fossil fuel deposits that we have later exploited. However beyond this it is largely a blank.
Looking at this graph it’s hard to escape the notion that civilisation may well be cyclical – and that maybe in another 100,000 years another civilisation may be developing their first city states thinking it’s all being done for the first time. At least with our plastic pollution, space debris and nuclear isotopes we will have left a record for any suitably advanced civilisation to discover – although with our mining of all the easy to reach fossil fuels, any future civilisation will be severely restricted in reaching an industrial level.
Looking on a wider scale
This fantastic graph (Glen Fergus) shows just how exceptional our current Holocene is. This baselines temperatures compared to the 1960-1990s average. Each section has a jump scale – so the furthermost right graph in units of 5000 years, but then we are in units of 200,000 years etc. We can see the large temperature fluctuations in the Pleistocene, with the brief window of optimal human climate from 127,000 to 117,000 years ago marked as the Eemian. Widening back further we can see just how hostile the Earth would have been to humans over the majority of the last 500 million years – with the temperature over 14 degrees C warmer 50 million years ago.
These graphs make you appreciate how lucky we are to be living in this tiny window of optimal climate – we need to make the most of it before the next climate cycle begins!