Has there ever a period in history when people were nice to each other and not killing each other?
In other words, since humans arrived, have the inhabitants of this planet ever enjoyed world peace?
To answer this, we first have to define period. Let's define period as a minimum of 50 years. If there are any periods of time without records, we will have to ignore those periods.
Now let's define not killing each other. By this, I mean no known battles, wars, or genocides on planet earth. I'm not referring to individual acts of violence.
As a curious side note, with over 5,000 questions asked on this StackExchange site, this is the first question to ever implement the peace tag. Well... almost... I just realized that I don't have enough rep to create a new tag, so perhaps a moderator will be kind enough to add it.