Humans have even changed their bodies since the middle ages. Menstrual periods are later. Maturity goes slower. People don’t die in 30 years.
Children having their parents die when they are 10 and get married at 20. Or children getting married at 10 and having their parents die at 20. All great choices which we don’t have to make and can moral high ground about.
I could ask why you think dating an 18 year old is fine but a 17 year old is not. Because modern research suggests the brain only finishes development at 25. But of course our sense of “morals” is solely based on arbitrary laws in < present time > in < present location >.