I don't believe that the homicide rate per capita is anywhere near historical levels. I don't have the information in front of me but I can recall reading that even Victorian England was much more violent than our days. Is your source referring to per capita rates or just absolute numbers? Almost any quantum relating to human beings in aggregate is larger today given the vastly greater population.
The Paleo debate continues. In a sense, it doesn't matter what happened to our ancestors in neolithic times as long as the Paleo diet works for people today. I don't think there are any certainties when it comes to most diets.