Is there a fundamental difference between war fought for reasons of belief and war fought out of self-interest? Is one more primitive than the other, or morally superior?
These deep questions are raised by the finding of a mass grave from 10,000 years ago by the shores of Kenya's Lake Turkana, now the earliest such site known.
They also resonate in the debate about how seriously to engage Islamic State, and whether to employ means of warfare that would actually eliminate the group instead of just contain it. In particular, the fight against Islamic State involves the question of whether it's good or right to go to war because the enemy is morally so bad.
Taken together, the battles of 10,000 years ago and today can help us clarify our answers.
The Lake Turkana site reveals about 27 skeletons, which appear to be from people killed in the same attack. (There are 12 complete skeletons, of which 10 clearly show that the person died violently. The evidence for the deaths of the partial skeletons is more circumstantial.)
The grave matters to anthropologists because 10,000 years ago, cultivation wasn't yet practiced anywhere near the site. That means the people who died -- and those who killed them -- were almost certainly hunter-gatherers. Their weapons included clubs, arrows and embedded stone blades.
There's a legitimate debate to be had about whether the attack is evidence of war or of something less, like a raid. But that question is less interesting than the debate about exactly why the attackers, whoever they were, killed men, women and young children, and left them where they fell.
The archaeologists who excavated the site speculate, on the basis of pottery found in the region, that there may have been surplus food stored, and that the attackers may have come to steal it. Another theory is that the goal was to take captives. No adolescent skeletons were found, suggesting that perhaps young people were taken as prisoners.
Notice that these ideas assume that some kind of self- interest must've been the underlying motive. Of course, we know from recorded history that wars fought for reasons of belief can also involve plunder and the taking of captives. Evidence of these practices isn't proof of underlying motive.
Could people fighting 10,000 years ago have had ideas capable of motivating action? The answer is unquestionably yes. They were fully evolved Homo sapiens, and had been for many millenniums. Religious icons and cave art date back substantially further in the human past. People who hold beliefs and make art can fight and kill for reasons they feel and articulate in language.
It emerges that these functional, self-interest-based explanations reflect a set of disciplinary assumptions about why humans fight. Many students of human behavior think that people act self-interestedly. Even when they speak in terms of ideology or cultural values, this can be described as a proxy for underlying self-interest.
In my view, it's an analytic mistake to think that self- interest always underlies human motivation. Culture and the beliefs that go with it aren't merely naked reflections of evolutionary impulses.
Once humans can think, they can define their own self- interest in ways that might conflict with "self-interest" narrowly defined. They can act based on moral values, laws and other kids of norms -- or against them.
This brings us to the fight against Islamic State, whose members are surely motivated by their beliefs, not their self- interest in the ordinary sense.
The countries around Islamic State's territory in Syria and Iraq all reject the Sunni militant group's ideology. But for the most part, they lack the calculus of self-interest that would be required for them to devote troops to the fight. Without those troops, Islamic State has so far shown it can continue to exist despite extensive bombing.
The exceptions are Kurdish forces, which have fought Islamic State to the extent compatible with their self-interest in acquiring territory; the Iraqi government, which has some interest in retaking Iraqi cities; and the Syrian regime, which has a self-interest in staying around in some form. Unfortunately, none of these powers has sufficient capacity or interest to defeat Islamic State altogether.
That leaves the U.S. and the European powers. Ideologically, all these abhor Islamic State. But none (so far) thinks its self-interest suffices to go beyond bombing.
Is this self-interested stance morally superior to going to war out of hatred for Islamic State and what it stands for? Or morally inferior? Both views can plausibly be sustained. Often it seems that morally inspired war is selfless and therefore less likely to be undertaken for bad moral reasons. But following self-interest may keep us out of wars that we fight foolishly, mistakenly believing that we can achieve our moral ends.
The upshot is that we must be clear-eyed about why we want to be rid of Islamic State. If our motives are primarily moral, we should keep in mind the risks that we will create unanticipated harm.
If, however, our motives are self-interested, we should be prepared to admit that we can tolerate Islamic State's continued existence.
In 10,000 years, when historians of the future try to untangle our motives for war, let's hope they can at least say that we knew what they were.
© 2016 The Washington Post