I've had this same conversation but concerning ages when normal things happen. Look at when people got married and had children in 1860 vs 1960 vs 2018. In this short amount of time people went from having children being normal from 12-14 to 18-30, to 25-40. Yes people still have children at young ages but it is more of a norm to do it later. Just look at all the HN articles talking about that the last couple years. Then listen to conversations when you hear about a 22 year old marrying a 16 year old, things get said like "pedophile" and "gross" and "thats just wrong." Even though not too long ago that was normal.

And that feedback is just from the States. Other countries and regions are different. Maybe here 18 is a magical age where you become an adult but in the far East its 16. In Amazonia it is 13. (I just made those numbers up, I do not know).

Makes you wonder, what is normal or moral to me that is just learned behavior and not really normal or moral?