As species, what impact did that have on us? Child abuse has a long history of being accepted, with child sacrifices in some cultures to forced marriages of children (not to say any of these events were super common, but there were cultures in which they were accepted even if not common). Look at 16th to 18th century and what happened to orphans of single mothers and it is horrible by modern standards. In some cases orphans were treated as child slave labor or worse (granted, they would grow out of it if they survived, while with actual slavery it was for life). Even into the 19th and 20th century we had children working in factories where dismemberment was all too common.
But around the start of the 20th century, that started changing, and today harming a child is one of the worse things that a person can do. Many would quicker forgive an ex convict that killed a rival gang member than someone who intentionally seriously injured a child.
I wonder if this is at all tied to drops in child mortality rates.