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Of course human beings have always fought wars. Of course a quarter of the adult males in the typical primitive society died violently, in wars and in fights.
(I'm using the banned word ''primitive'' here because it's shorter than ''hunter-gatherer and horticultural non-state societies'', not because primitive peoples are inferior.)
And of course many people don't want to admit how violent our past was, because they are afraid that our past will also define our future. But it's hard to believe we are still having arguments about this long after the evidence is in.
The occasion for these intemperate remarks is the controversy that has broken out once again since American anthropologist Napoleon Chagnon published his memoirs, Noble Savages: My life among two dangerous tribes - the Yanomamo and the anthropologists. Chagnon does not bear fools gladly. But then, he has had to contend with quite a few fools in his career.
In 1968, Chagnon published a book called Yanomamo: The Fierce People. It was about his research among a group of about 20,000 people living in complete isolation in the Amazon forest. They were split up among 250 little villages which were perpetually at war with one another.
At the same time, other anthropologists were documenting the same state of constant warfare among the few other surviving hunter-gatherer and horticultural groups that had previously avoided contact with ''civilised'' societies, especially in the highlands of New Guinea. Similar pre-contact behaviour was being confirmed in other groups like the Inuit.
And of course there was ample evidence that bigger ''tribal'' societies, from North American Indians to the Maori of New Zealand, had also spent much of their time at war with one another.
This new perspective was most unwelcome to people (including anthropologists) who still clung to Jean-Jacques Rousseau's comforting myth of the ''noble savage'' living at peace with his neighbours and the environment, but the evidence was overwhelming.
Chagnon's book was an instant best-seller and remains the most widely used anthropological text yet, but it also ignited a firestorm that still flares up occasionally.
Chagnon did not just say that primitive people were always at war, and that a lot of them died from it. He said there was a genetic component in this behaviour.
Like all good anthropologists, he did genealogies of the people he studied - and he discovered that men who had killed other men in battle had three times as many children as men who had not killed. Human beings are ''imperfectly monogamous'', but in groups where force is relatively unconstrained the best warriors get more wives.
Therefore, Chagnon said, they are more successful in passing on their genes.
He did not say culture and environment play no part in moulding human behaviour. He was simply documenting what should have been obvious: that if all human societies fight, then we must, among other things, have some genetic predisposition to do so.
We are not necessarily doomed to fight in groups, but we are (unlike cows and pigeons) able to do so.
In saying this, Chagnon outraged two overlapping groups: the anthropologists of that generation whose intellectual roots were in Rousseau and Marx, and people who feared primitive groups would be more vulnerable to exploitation
if they lost the protective myth of the peaceful, noble savage.
The tactics of Chagnon's critics were ruthless and even slanderous: he was accused of giving the Yanomamo weapons and urging them to fight, even of deliberately causing a measles epidemic among them. He's a combative sort, and his recent book shows the scars of fighting off unjust accusations for more than 40 years.
He would have fared better if he had dropped the other shoe. If he had known as much about history as he did about anthropology, he would know that the level of violence in human affairs has dropped drastically since the rise of civilisation - precisely because we do now live in bigger societies.
Even the earliest mass societies lost far fewer people to war than the little societies of the more distant past, because it was no longer the entire male population that went to war. The battles were far worse than those of primitive warfare, but most people never saw a battle.
Even the dreadful 20th century follows the trend line. At least 50 million people were killed in the two world wars, but that was out of a global population that was nearing 2 billion people: a 3% fatal casualty rate for war over a period of 30 years.
It's very unlikely any pre-contact primitive society ever had a casualty rate that low. And in the six decades since 1945, far less than 1% of the world's people have died in war.
We are shaped by both our genes and our culture, and our culture no longer accepts war as natural and inevitable. We are not better people than the Yanomamo, and we're very far from perfect. But our past does not define our future.