In modern times, we worry about our kids’ exposure to simulated violence on television or in video games and whether it desensitizes them to real-life atrocities. But in many past eras it may have been actual violence, not the made-for-TV variety, that desensitized children to more of the same. Think of the children who grew up in cultures where they would have seen real-life killings and torture up close by the time they were five, six, or seven years old. In some cases, they might have even participated in it.