There is no historical evidence that corporal punishment harmed society. Why is corporal punishment discouraged?
In our culture, the real change in attitude occurred after WWII and, to some degree in response to it. GIs brought many things home from the war. One of those was harsh discipline. In response to their experiences (Great Depression; World War) and all that that entailed, they were also committed to giving their children a better life than they had. Put those things together and you have an environment of extremes which then led those children to grow up way more sensitive than their parents and to be guided by that increased sensitivity when they parented their children. You end up with a cultural paradigm shift away from corporal punishment.I must disagree with your premise that no historical evidence exists. For at least a couple thousand years, young boys in many cultures were trained with corporal punishments resulting in them being well disciplined, tough minded, aggressive and frequently violent. The connection is largely anecdotal, but compellingly consistent.I, for one, can see the usefulness of corporal punishment, at times. It should be used sparingly and with the understanding that it may be effective, but also may teach things (behavior / relationships) that you don’t want to teach. I used to teach parenting skills and consistently told parents that it was okay to swat your child (think of a toddler putting themselves in danger), but only once per incident. Anything more was to satisfy the parent, not train the child. Welts, bruises, scrapes, etc. are not an indication of good parenting, in my view.