You're making my day. This is one of my favorite topics to discuss 
And if you would be so kind as to relink the article by Dr. Peter Gray, I would appreciate taking a gander at it. I was unable to find it by googling his name and I think I remember you linking it in this thread several pages ago, though I don't remember exactly where or precisely which link I'm looking for.
Likewise.
And it's refreshing to have an actual debate on these topics (on the internet of all places!) that doesn't devolve into a screaming flame war.
You can find the article
here. In the interest of full disclosure, it is hosted on a site with a definite political bias--part of why I looked up the author's credentials and sought out corroborating evidence when I originally came across it. Going back over it, it turns out he actually mentions the Yanomami tribe specifically.
What I find more interesting are the social mechanisms he describes, which he hypothesizes are responsible for the relatively idyllic state of these societies. Even if all his contentions about modern and historical hunter-gatherers were shown to be wrong, those ideas sound like they could work.
Anyway, I assumed we were drawing the line at the Neolithic Revolution, where we began domesticating plants rather than simply growing them, and thus began building cities and setting up formal governments. I took this as the line because it is the cleanest place to make the separation, and is where most anthropologists draw it as well. The transition from pure hunter-gatherer to agrarian happened gradually (and incompletely) over tens of thousands of years (with many groups cultivating plants while remaining semi-nomadic), while the Neolithic Revolution was only 1-2000 years and represents a much more dramatic change. The other reason I think this is a better place to draw the line is that this is but a tangent on a discussion of the merits of anarchy vs. statehood, rather than agricultural vs. hunter-gatherer. It is also important to note that the switch to agrarianism and semi-agrarianism was not a choice so much as an adaptation of necessity, not the least of which was caused by our own over-predation of large mammals. A return to hunter-gatherer lifestyle would not be feasible without a return to hunter-gatherer population levels.
I confess, it sounds like you're better versed on the details of this period than I am. My understanding is that the increase of violent and hierarchical behavior occurred on a case by case basis, either as a result of the social changes stemming from a group taking up agriculture, through contact with such a group, or through the indirect effects of an agricultural society's presence. For example, in the article you linked to about chimps, deforestation was mentioned as a possible cause for the behavior. Even groups that had never encountered humans could have been affected by the shrinking habitats and increased competition due to an influx of displaced animals caused by logging on the perimeter of their jungles.
Regarding the over-predation hypothesis: Most discussions of the neolithic revolution that I've come across attribute it to the changing climate at the end of the ice age. In other words, it's not so much that we killed off all the animals and had to start eating plants, but that the environment changed and we adapted while other species did not. Apparently there is some debate about which of these theories is most accurate.
In general, I do agree that the advent of agriculture brought on greater violence, but that is to be expected with greater population density. I do not have reason to believe, however, that the amount of violence relative to total population was significantly higher. In my view, the chances of dying a violent death at the hands of other homos were more or less the same, with a slight increase right after the advent of agriculture. The problem with talking about pre-agrarian societies is that low population density means less evidence, compounded by the fact that non-sedentary lifestyles also leave less evidence. This is why I see the argument from ignorance in many Rousseauvian "noble savage" arguments.
It definitely seems like it would be harder to say for certain under the circumstances. However from what I've read the hypothesis that pre-agrarian tribes were less violent is informed partially from observations of current hunter gatherers. It's not 100% conclusive, and you make an interesting counterpoint that such behavior could have adapted in response to previous conditions of violence. Still, I wouldn't call it arguing from ignorance. Given what evidence we have, it strikes me as more reasonable to at least tentatively conclude that prehistoric hunter-gatherers were also more peaceful than their settled counterparts.
Two main points I would base this conclusion on are that A) Cooperation within the tribe was more critical to survival, as ice ages suck and don't leave a lot of room for bickering lest everybody starve and B) I don't see how there would be much incentive for one tribe to attack another under these circumstances.
The relative wealth of each tribe is capped by what can be carried, so tribe A is unlikely to have significantly more wealth or resources than tribe B, and even if they did what would be the point of trying to take it when you can't carry two tribes worth of stuff? There's a reason a lot of GM's handwave carting all the loot back to town after an adventure.
And again, in an ice age every tribe member becomes a critical resource. Why would you risk attacking a better equipped tribe when you could just hunt game animals? I could see this happening briefly in times of scarcity, but there would only be a brief window in which this would be effective before things stabilized. (Either by a return to previous levels of abundance, or everyone being equally worse off.) Even if your goal was to acquire slaves, the trust and cooperation required by the hunter gatherer lifestyle makes this a risky prospect at best. Cannibalism could be a potential motivation, but between
the health risks and fact that
humans are generally more dangerous than other potential prey, I doubt the idea would be sustainable as a widespread practice.
In short, raiding doesn't really become a viable strategy until you have settlements.
There are other examples of wounds in paleolithic people that were clearly made by arrows or spears.
If the Yanomani tribe's violence cannot be seen as reliable evidence because of the influence of agrarian societies, neither can modern hunter-gatherer peacefulness. They could very well have developed such avoidance strategies as a result of interaction with better armed agrarian societies, and regardless, such avoidance strategies could be the reason those societies in particular survived with their way of life intact.
Chimp warfare is a well-documented thing. Many other apes also demonstrate intraspecies violence. Chimps are our closest evolutionary relative, followed by the other great apes, and while it isn't conclusive by any means, it lends credence to the idea that intraspecies violence was present in a common ancestor and thus predates humans by a great deal.
My statement about killing off Neanderthals and Denisovans was partially made in jest because we obviously did absorb their populations into our own. However, it is extremely likely that there were also conflicts between them and us, and we were clearly the victors. If they were close enough to reproduce, they were close enough to compete for resources as well.
Regarding all this: While I'm not contending that violence never occurred in hunter gatherer societies, the relevant point in the context of this discussion is whether it occurred
less often than in settled communities. Providing evidence of some violence does not indicate equal or greater violence, particularly in the face of evidence that the neolithic revolution did in fact trigger an uptick in violent conflict.
Bringing this back to the original discussion of anarchy, one important thing to note is that anarchy defines "violence" a bit more broadly than most people are used to. The
Non-Aggression Principle, which forms the backbone of anarchist philosophy, defines aggression as "any encroachment on another person's life, liberty, or justly acquired property, or an attempt to obtain from another via deceit what could not be consensually obtained." As a result, anarchists see any external government as a form of aggression against it's people, leading to the maxim: "If the individual has the right to govern himself, all external government is tyranny."
Naturally, governments tend to disagree with this notion.
I bring this up because although you could argue that
physical violence has decreased in modern societies (I have my doubts, but the argument could be made), from an anarchist perspective, the prevalence of governments and hierarchical power structures makes modern society
unequivocally more violent than the stateless hunter-gatherer communities believed to have existed prior to the neolithic revolution.
Further, even if we were to conclude that ancient hunter gatherer societies were roughly as violent per-capita as the agrarian communities that followed--with the spike in violence during the neolithic revolution being a transient increase rather than an upward trend--that still doesn't address the claims that modern hunter gatherers are more peaceful and egalitarian. The existence of such communities demonstrates that anarchy can work without devolving into violence and aggression, regardless of where they sit on the historical timeline.
To address an earlier point you made: You are correct about the hunter-gatherer lifestyle not being sustainable with humanity's present numbers--though many would argue those numbers aren't sustainable anyway. Nevertheless, it does present an obstacle, and any social controls which might conceivably reduce our population to a size where it would be viable would also violate the
hell out of the NAP.
Personally, I would not favor a return to a hunter-gatherer lifestyle. Although I am convinced it offers many benefits I would rather we find a way to adapt the social mechanisms which reinforce voluntary, peaceful cooperation without losing too much of what we presently have. Granted, I'm not particularly sure how we would achieve that. The first hurdle is just convincing people that anarchy doesn't look like something out of Mad Max: Beyond Thunderdome.* Figuring out what a functional anarchist society
would look like requires getting people on board with the idea of creating one in the first place.
*
Despite the fact that Bartertown was
clearly a monarchy, and every single conflict in that film stemmed directly from somebody violating the Non-Aggression Principle.
I want to hit everyone who automatically assumes that welfare and poverty = not working hard, and that hard work apparently automatically equals success and being paid well. That... is not how things work. Or have ever worked.
Hear fricking hear!
Especially considering how much goddamn
work living on public assistance is. The lower classes labor to support the luxuries of those above them, that's how every stratified social system works. But since it's such a shit deal, the upper classes usually try to paint their position as being based on merit rather than exploitation, and trick those under them into fighting among themselves. All this bitching about welfare and the poor amounts to complaining that you have to occasionally
feed your servants. Plus it sidesteps the fact that each politicians' paycheck accounts for way more tax money than some poor schmuck on welfare is getting.
