Human population overshoot–what went wrong?

There are seven billion people on earth now. I originally thought that the primary reason for the recent human population explosion was that fossil fuels enabled a larger food supply and better medicine, and thus a higher population.

Figure 1. World population from US Census Bureau, overlaid with fossil fuel use (red) by Vaclav Smil from Energy Transitions: History, Requirements, Prospects.

While the addition of fossil fuels is part of the story, after reading Craig Dilworth’s Too Smart for Our Own Good: The Ecological Predicament of Mankind, I realized that there might be another contributing factor. Animals of all types (presumably including humans) have instincts and learned behaviors that prevent population from rising without limit.

Dilworth talks about an experiment in which a few Norway rats were put into a cage of 1,000 square meters and provided plenty of food and water for 28 months. If they had produced as many offspring as theoretically possible, there would have been 50,000 of them at the end of experiment. If they had maxed out at the 0.2 m2 allowed for caged rates in laboratories, there would have been 5,000 of them. What actually happened is that the population stabilized at less than 200.

As I read about the mechanisms for keeping the population of most animals down, it struck me that there seem to be parallels in humans. Dilworth talks about many species being “territorial,” and how aggression among groups is one of the first approaches to keeping population down. When that fails (as with humans’ globalization), social power structures and hierarchies become more important. This seems to happen with humans also:

Paul Buchheit, from DePaul University, revealed, “From 1980 to 2006 the richest 1% of America tripled their after-tax percentage of our nation’s total income, while the bottom 90% have seen their share drop over 20%.” Robert Freeman added, “Between 2002 and 2006, it was even worse: an astounding three-quarters of all the economy’s growth was captured by the top 1%.”

This sounds exactly like the kind of hierarchical behavior observed in the animal kingdom when social species get stressed. If there is not enough to go around, resources that are available are concentrated in the hands of those at the top of the pyramid, marginalizing those at the bottom of the pyramid. If total resources are inadequate,  population at the bottom of the pyramid is reduced, leaving those at the top untouched.

In this post, I discuss some of the issues raised by Dilworth  and the parallels I see with humans. I also add a perspective of hope. Continue reading