What has always bemused me about this question is that the 'social' laws are fighting the biological laws .. what I am trying to say is that a girl comes into puberty at average 13 and therefore can conceive and produce offspring .. a boy is at his high at 18 (sorry, fellas most of you here now on the decline

) This would be a perfect match according to nature.
If you have any sort of religious beliefs, this is what your God should be telling you .. is it not ? as he supposedly created you .. Ok .. yes, I am an atheist; but it is the most religious people that tend to argue against under age sex.
Just that the way we have evolved socially and over population, lack of housing, makes it rather difficult for 13 year old girls to bring up a child of her own, because we are at this age still providing education, fun things to do and labour laws, etc., Better all around, but still this battle going on. It does seem strange that a day before your 16th birthday it is considered wicked and illegal; the next day 'that's fine'.
Remember when Jerry Lee lewis married his 13 year old bride ? I felt strange about that one as only young myself.
Seems in some American states, the age of consent for women is 16 and boys 18 .. that is weird.
Anyway, we all know the difference between paedophiles and early relationships