Parents have been spanking children for millennia. 50 years of scientific evidence says they were wrong.

More rubbish research. Gershoff is well known for advocating smacking bans and producing research which she thinks supports her notion. But here’s the funny bit. Read this bit (our emphasis added):
“What’s more, the analysis finds evidence that spanking is associated with troubling outcomes — like increased aggression, increased anti-social behavior, and mental health problems later in life. The size of these negative effects are SMALL, the study notes, and there’s NO PROOF that spanking specifically caused these behaviors later in life.”
And
“For one, researchers can’t conduct spanking experiments where they randomly assign children to be hit. And it’s also POSSIBLE that “bad” children are just spanked more, and are also generally MORE AGGRESSIVE and anti-social throughout their lives. But Gershoff SUSPECTS spanking does LEAD to these detrimental outcomes. Or, at the very least, she makes the CONVINCING case that spanking doesn’t do any measurable good.”
In other words, it’s a great theory – but we all know from personal experience that it’s rubbish.
Moving on…….     
For 20 years, developmental psychologist Elizabeth Gershoff has been chasing a question: Does spanking actually do a child any good?
“As far [back] as we have written records, people have been hitting children,” Gershoff tells me. Today, spanking — hitting a child on the buttocks with an open hand — is still incredibly common. A 2015 Pew survey found that 45 percent of parents in the United States have spanked.
Given this long history, is it possible that parents throughout millennia — many with the best of intentions — were doing the right thing?
Gershoff is now even more confident in the answer: It is a resounding “no.”
In a recently published meta analysis in the Journal of Family Psychology, Gershoff and University of Michigan professor Andrew Grogan-Kaylor sift through 75 studies, for a total data pool of nearly 161,000 children, and find “no evidence that spanking is associated with improved child behavior.”
What’s more, the analysis finds evidence that spanking is associated with troubling outcomes — like increased aggression, increased anti-social behavior, and mental health problems later in life. The size of these negative effects are small, the study notes, and there’s no proof that spanking specifically caused these behaviors later in life.
READ MORE: http://www.vox.com/2016/4/27/11510118/spanking-children