That's about it. I.e. hominid canines shrank in size in a short span of time. Since primate canines are used primarily on each other, a sudden decrease in their size would indicate intense selective pressure away from using violence to solve problems. Ultimately, humans aren't subject to their inborn tendencies if they don't want to be. Any rock concert should be enough evidence to indicate we can overcome our inborn fear of loud noises, for instance.
Children are extremely cruel to each other.
That's one reason why intense parental involvement is a requirement for our children to grow up into civilized adults. No involvement, no civilization. The cartoon shows a teenager reading a note left for him on the fridge. Hi Honey, Dinner is in the fridge. Breakfast is in the freezer.