The fact alone that atomic weapons leveled whole cities, millions were gased, and entire nations were at war with each other (tanks and all) points to a more violent time JUST RECENTLY. And that's just recently.
Then there is the scope of all human history, full of empire-ridden, ligament-stretching, slavery-propping, native-slaughtering, ripping hearts outta the chest barbaric shit. And, this is to say nothing about what cavemen might have been like, who go back MUCH longer than just the few, meager thousand years we have had "civilization" (if that's what you want to really call it).