Quote Originally Posted by DuncanONeil View Post

No matter how you think about it the species has divisions. Some are meaningless. But perhaps the greatest division is, although somewhat arbitrary, child and adult. Activities routine and normal for the adult are restricted from the child. Unless one wishes to say that no human activity is to be denied the child. Which would include sex, drugs, war, work, or any other number of things. Carried to that extreme, and many today bemoan the loss of childhood, means we will not have children. Merely little adults, which is how some actually refer to children already!
As two other contributors have pointed out, historically speaking, childhood is one of those meaningless divisions you mention. Obviously, younger people are physically unable to do some things, but up till the last few centuries the rule for everything was that when they're big enough they're old enough.

In the 10th Century "Njal's Saga" (which might be called the first recorded celebrity biography) the hero at age 12 asks his father to take him along to a feast, and is told that he can't come because he gets too violent when he's drunk. So he steals a cart-horse and comes anyway, gets into a fight and kills another boy. All this is reported as the story of a berserker who started young, but with no idea that there was anything intrinsically strange about such behaviour in a "child". Compare with a couple of recent cases of murders by preteens in the UK, where the media response has been not only a perfectly reasonable outrage at the details of the killings, but also an almost superstitious horror as if there were something monstrously unnatural about the perpetrators, purely on account of their age.

The reason for the invention of childhood, in the opinion of historians, was firstly the need for a higher level of general education in more technically advanced societies. It therefore became necessary to class people as schoolchildren who had previously been classed as young adults. This became complicated by the Victorian obsession with innocence, narrowly defined as ignorance of sex; moralists took the completely artificial redefinition of childhood as real, and equated teenage sex with child abuse. The resulting conventions were so hammered into Western society that when Europeans encountered cultures where sex still started at puberty, they took it as evidence of the savages' immorality and set out to save them by teaching their children shame.

There are areas where it is a genuine advance of civilisation to restrict young people's access to adult practices: young Njal's drunken brawls were the mark of a barbaric culture. But if we are going to debate the question of chidren's sexual behaviour, it must be on the basis of known realities of physical and mental health and the welfare of society, not an undiscussed assumption that some things are just wrong because it's always been so.