Gimme that old-time population growth
In discussions of human population growth, I tend to take the view that it's mostly driven by underlying material forces - genetic imperatives, resource accessibility, climate, geography, geophysical history, etc. I usually give short shrift to the notion that culture has much to say about it in the big picture, both because culture tends to be local (I'm an unabashed globalist in this matter) and also because culture seems to me to be more of an effect than a cause in the positive and negative feedback loops that control the various aspects of human growth.
Supporters of indigenous cultures regularly raise the objection that native societies have lived for long periods in balance with their surroundings, showing little sign of growth in numbers. My usual rejoinder is that these examples are accidents of location, exceptions and outliers that do not invalidate my central materialist premise. Needless to say, this rebuttal doesn't go over well with the indigenist crowd.
I recently became aware of the HYDE database. It contains, among other interesting data, a population reconstruction for the last 12,000 years. It seems to be the most detailed and authoritative set of estimates so far. I decided to graph their data for the period 10,000 BCE to Year 0. I chose this period so we could see how population behaved before the advent of the modern influences that are normally implicated in growth: monotheistic religions, capitalism, fossil fuels, and communication/propaganda technology like the printing press.
The graph is unambiguous: world population apparently followed an exponential growth curve that was consistent for over 10,000 years (though it does seem to accelerate somewhat as time goes on).
The smoothness of the curve makes me wonder about the reconstruction techniques used for the HYDE data - it seems to imply mathematical interpolation between necessarily imprecise data points. However, it seems clear that an exponential trend has been a feature of human population growth since the very beginning, through the rise and fall of a wide variety of cultures.
Fortunately, since about 1980 global population growth has dropped back from exponential to "merely" linear growth. In my view that deceleration is probably due to issues like overcrowding (possibly leading to the version of Hans Selye's "General Adaptation Syndrome" seen in John Calhoun's "Mouse Utopia" experiments), rising resource costs, declining economic opportunities and rising social instability. However, with our growth still adding 80 million people a year to the planet this is pretty small consolation.
HYDE presents (gridded) time series of population and land use for the last 12,000 years ! It also presents various other indicators such as GDP, value added, livestock, agricultural areas and yields, private consumption, greenhouse gas emissions and industrial production data, but only for the last century.
The HYDE numbers are also given in the Wikipedia article on world population estimates.
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The graph begins with the Toba catastrophe and uses an estimate of 20,000 people who survived that bottleneck. Whether that number was tens of thousands more or a few thousand less is immaterial given the time scales involved.
The shaded sustainability periods are my estimates. When our numbers were below 7 million (before 7,000 BCE) Homo sapiens was a sustainable species. As our numbers grew from 7 million to 100 million over the following 6,000 years we became progressively more unsustainable. Since 1000 BCE when our population rose past 100 million, we have IMO been categorically unsustainable. In the last 1,000 years we have entered the explosive overgrowth phase typical of a "plague species".
There is no point arguing about whether the human presence on the planet is sustainable until our total population has again subsided below 100 million. Until that happens, the answer is a categorical "No".
Even then, our species would be unsustainable if the number of births was to rise above the number of deaths. This presents what seems to us to be a moral conundrum around the issue of death. For a very small society that understands that the survival of everyone is in peril if this principle is violated, the moral issues will inevitably be quite different.
