And you know what? It doesn't matter. The exact percentage of the population that got murdered is only one portion of the basic thesis that the present is the best time for the average human being to be alive ever. While the typical ancient adult may or may not have been murdered, the average ancient human would be dead before their 15th birthday due to disease (most common), malnutrition, or predation.
The worst countries today for infant mortality are in central Africa, with countries like Chad, Nigeria, and Somalia averaging a heart breaking ~11% mortality rate for those under the age of five. While I wouldn't run around shouting "this is fine and we should do nothing about it" compared to the entirety of human existence this is an astounding stat. There are royal families a few centuries ago that did worse than 11%.
No, these benefits are not evenly distributed. All in, you'd much rather be born in the US or the EU than in say, Chad. And quality of life does not improve linearly; you would much rather be a hunter gatherer than someone in an ancient Greek polis, where you were both more likely to be enslaved and where you'd probably live an even shorter and more disease ridden life. But if you had to pick any point in time to be a random, average person, now is the best time in all of human history to pick.
That study indicates that violence-based mortality is high in a few hunter-gatherer societies, but not in all of them, and also not in societies adjacent to these.