Your chart indicates that mass violence began about the same time as agriculture (about 12 thousand years ago, give or take depending on the area). You might want to pay better attention to the data that you are using to make your points in the future to be sure that it actually does make them, because that link/chart does not.
"The relatively recent past was undoubtedly more violent than now, but this does nothing at all to shine a light on what our ancestors were doing 25,000 years ago or 100,000 years ago, much less 200,000 years ago, when homo sapiens first emerged. When I write about the largely peaceful and egalitarian history of our ancient ancestors, a topic that I have thoroughly researched and written extensively about, there is always some guy who has to insist that no, the truth is that humans have always been violent and warlike, usually based on evidence that doesn’t actually demonstrate that, as with Pinker’s book."
"There is no archeological evidence of warfare or large-scale violent death of any kind from our distant past. In fact, the massacre at Jebel Sahaba, about 13,000 years ago is widely recognized as the first site of mass armed conflict. Therefore, those who are making assertions about pervasive warfare before that time are basing it not on archeological evidence, but on notions that fit their preconceived ideas and that ignore realities that do not mesh with that preconception."
Edit:
“There is really no actual scientific support for warfare in the Paleolithic era, and there is an overwhelming indication that pervasive violence and mass conflict only becoming prevalent in the past 8,000 years or so. R. Brian Ferguson, an anthropologist who studies war says that after studying the published work of dozens of other researchers he finds no evidence of war in the Stone Age, prior to 13,000 years ago. His findings were published in 2013 as a chapter in the book, War, Peace and Human Nature. “Views of human nature as inherently warlike stem not from the facts but from cultural views embedded in Western thinking.”
Here's what Scientific American has to say:
“Many social arrangements impede war, such as cross-group ties of kinship and marriage; cooperation in hunting, agriculture or food sharing; flexibility in social arrangements that allow individuals to move to other groups; norms that value peace and stigmatize killing; and recognized means for conflict resolution.
These mechanisms do not eliminate serious conflict, but they do channel it in ways that either prevent killing or keep it confined among a limited number of individuals. People are people. They fight and sometimes kill. Humans have always had a capacity to make war if conditions and culture so dictate.
But those conditions and the warlike cultures they generate became common only over the past 10,000 years — and, in most places, much more recently than that. The high level of killing often reported in history, ethnography or later archaeology is contradicted in the earliest archaeological findings around the globe.”
