Just How Old?

I have been debating(sort of!) recently with a user on here the age of consent.

Basically it seems girls under a certain age just haven't got the ability to understand the implications of having sex at that point in their lives.
PLUS any guy who is involved and over a certain age MUST be a paedophile (nonce being the term used) , by virtue HE should know better.
This comes on the back of a recent report on the brain that we(homo sapiens) seem not to have a fully developed 'adult ' brain until the age of 32.

From this my step brother is being called a paedophile..because he obviously took advantage of me(see my 'beginnings' post). Oh NO HE DIDN'T! ..shades of panto here??.

So.. Can I have YOUR thoughts please?
Are girls incapable of giving consent BEFORE the actual UN designated age?
Girls by that age are certainly fully capable of becoming pregnant.. Periods can start as early as 10 so to say we have no understanding of sex is wrong and a ridiculous naive statement to make.
These days I think girl's are MORE aware of sex, their bodies and their place in the world than EVER before.
Or was that JUST me? I think NOT!

My step brother is a great guy who would be mortified to hear of people thinking of him that way.?
On the other hand societies rules (usually) tell us what is WRONG and right..which sensible people interpret for themselves(obviously after the age if 32??) and ignore the nonsensical ones