Harvard psychology professor Steven Pinker, in The Better Angels of our Nature: Why Violence Has Declined (Penguin Books, 2011), argues that human violence has declined. Violence was much more widespread in primitive societies than in historical times, and more widespread in the Middle Ages than in the twentieth century — yes, even worse than the First and Second World Wars. After reading his lengthy but quite readable book, I am convinced — violence between humans has indeed declined. It’s an engrossing and ground-breaking book, by the way; everyone from Peter Singer to the Wall Street Journal has praised it.

However, there are a few small points I want to raise concerning the book. Specifically, violence towards animals has increased; and the peace between humans is largely dependent on our relative affluence, which in turn depends on our exploitation of natural resources, which are now seriously depleted.

Prosperity and the Decline of Violence

There’s an obvious correlation between the decline of violence and the rise in prosperity. It is hard to tell whether increased prosperity is the cause or the result of peace, but they are clearly connected; most likely, they feed on each other.  We have become more peaceful over the last few thousand years, and we are also more prosperous.  A higher standard of living allows for literacy, democracy, communication, education, and other things, all of which further peace.  Peace also propels prosperity forward through trade.

Pinker briefly considers, and then dismisses, the idea that prosperity is the cause of peace. It’s easy to see why it is so perplexing a topic, because in the short run violence can further the prosperity of one group at the expense of another.  This is the story, in short, of the Roman Empire, a violent regime which conquered other lands, raked in huge loads of wealth, became very rich and then fell when it could not expand its borders any further.

But the example of the Roman Empire is misleading. Rome did not increase the world’s prosperity; it simply relocated this wealth from other parts of the world to Rome. “Looting and pillaging” is not a way of increasing prosperity overall. Increasing affluence, as Pinker rightly notes, does not automatically result in a decline of violence, but prosperity is a necessary ingredient.

Violence Against Animals and Nature

The link between prosperity and peace leads to my second concern: much of our prosperity is based on violence against the nonhuman world, specifically animals and nature. It’s true, as Pinker says, that attitudes towards animals have improved in the last few decades. But any suggestion that human violence against animals has declined since prehistoric times, either per capita or in total, is just false.

In fact, the exact opposite has happened; violence against animals has progressively increased, and is greater today than it ever has been in history. The percentage of mammals (by biomass) who were domesticated by humans at the beginning of agriculture was very low, certainly below 1%. Today, over 90% of all mammals are humans, their livestock, and their pets. Pets are reasonably well treated, but livestock are treated abominably.

This has gotten much worse recently. Just during the time of the “Long Peace” which Pinker has written so glowingly about, factory farm usage has exploded and worldwide meat consumption per capita has increased steadily. While affluence seems overall to decrease violence between humans, prosperity is exactly the thing increasing human violence towards animals. Everyone wants meat.

We have not become less violent. We have simply shifted our violence from other humans to other animals and to inanimate nature.  Our prosperity depends on exploitation of natural resources which can be leveraged with technology, but which are nevertheless finite.

Our violence towards nature is already recoiling against us. A recent study published in Science magazine stated that climate change is a cause of increasing violence.  The abstract says, “We find strong causal evidence linking climatic events to human conflict across a range of spatial and temporal scales and across all major regions of the world.”

We live on a finite planet and the era of fossil fuel abundance ended about a decade ago. If our prosperity is dependent on violence against animals and exploitation of natural resources, and if these natural resources disappear, what will happen to our prosperity? And if our prosperity disappears, what will happen to the better angels of our nature?  Will they be pushed aside as we return to a more brutal world?  Inquiring minds want to know.

Cycles of History

A third problem is that history tends to go in cycles.  In The Fourth Turning, Strauss and Howe say that American society tends to go through fundamental crises every 80 to 100 years. Peter Turchin and Sergey Nefedov argue in Secular Cycles that civilizations go through cycles about every 300 years, going through phases of growth, stagnation, crisis, and decline.  During the decline phase, the elites fight among themselves, the condition of the non-elites gets worse, and the government is continually weakened due to declining revenue, leading to a collapse and depression.

The “Long Peace,” as Pinker describes the period since the Second World War, could fall within one of these 80, 100, or 300 year cycles.  Strauss and Howe argue that each cycle of American history lasts on the order of 80 to 100 years, and the last cycle ended in 1945.  In their analysis, the so-called Long Peace would fall entirely within the upswing of the current historical cycle.  Turchin and Nefedov’s analysis doesn’t consider the case of American civilization, but if you consider our experiment to have started in 1775, it doesn’t take much imagination, considering the current environmental, climate, and resource depletion crises, to see that we could see its disintegration and disappearance by the year 2075, if not earlier.

None of this proves Pinker wrong about the past.  But it does raise serious doubts about the future. Given what we know about the multiple environmental crises and the total political paralysis in dealing with or even acknowledging it, we cannot count on the prosperity which has given us peace to continue to do so.  A lot of people who are discussing the decline of resources talk openly about mass starvation, huge epidemics, and a relatively rapid decline of human population.  Some, such as James Hansen in Storms of My Grandchildren, are talking about human extinction.

In such a world, will nonviolence and peace continue?  This is the question which I think Steven Pinker and Peter Singer (who gave the book a glowing review) need to be thinking about.