You're confusing interpersonal murder with tribal conflict.
Personal murder is tightly controlled now. But this is a fairly recent development. In many periods it was tolerated under various forms, including slavery, blood feud, honour killings, and state-sanctioned murder as punishment, or political process.
It's only in the last few centuries that it's been prohibited, and the prohibition in practice is still partial in many countries. (See also, gun control.)
Tribal murder has been the norm for most of recorded history. There are very, very few periods in very, very few cultures where there was no tribal/factional murder in living memory, and far more where it was an expected occurrence.
And technology has always been close by. Throughout history, most tech has either been invented for military ends or significantly developed and refined for them.
You are juxtaposing murder with killing. Every culture has a strong taboo against unlawful killing, i.e., murder. What counts as murder has changed, but the taboo against murder itself has not.
But doesn't that distinction kind of prove the point? Essentially killing people is fine when society approves and not fine when society doesn't implies that there is no built in norm against killing, its just society's "rules".
Read carefully. Neither me nor bluegatty claimed humans were inherently biased against killing. We claimed that humans were inherently biased against murder - and the universal taboo proves our point.
So your claim is that there is a universal taboo against things that there is a universal taboo against? If your definition of murder is taboo killing, it is very curcular to claim there is a universal taboo against it since by definition it is only murder if there is a taboo. Thus the claim kind of proves the opposite - if you have to limit it to murder then it shows there is no built in bias, as the definition of murder varies from society to society and essentially means killing in a way the society doesn't approve off. There is no possible way for there not to be a bias against murder since if a society is ok with it is ceases to be murder.
> Read carefully
I did, perhaps read my post carefully.
To be fair, it doesn't really seem worth mentioning to say humans are inherently biased against murder, which we then agree is a killing against that society's norms. Because the definitions of "murder" vary so hugely, you're essentially just saying "there is a taboo against breaking the arbitrary rules of your social group."