That wasn't my point though. And I wasn't in any way commenting on age with specific regard to Johnson's situation for those that may think these comments are alluding to that issue.
Basically it is UK society's mores that have decided this arbitrary cut-off based on what the UK population will accept (not on any scientific basis but from a religious one). Fact is that, as a species, human females are sexually mature, able to reproduce and to make responsible mothers at 13-14 and in many societies around the world that is accepted and many are married off (Africa, Asia and maybe even parts of South America) between the ages of 13 and 16. Nature is rarely wrong in deciding when a species is capable of, as in mature enough, to breed.
That does not mean I agree with a very mature male taking a very young but sexually mature female as a mate ! Though that is often the way in some societies, security over personal preference. And of course this is just a conversation on the scientific aspects of sexual maturity, ignoring that fact that modern Western society prefers to see young adults, of either sex, educated and experienced before creating a family.
Basically what I'm saying is that nature disagrees with people when they say that young females are not mentally able to cope with having sex even though sexually mature. It is society that has made that decision. Many millions of mature women would probably agree with that.