There's nothing scientific about consent.
The entire concept of consent itself is man-made -- it's a reflection of societal norms, ideal, mores, taboos, or whatever else you want to use as a term to label the reason we have laws around it.
I don't happen to agree with the pedophilia or NAMBLA red herrings that get thrown out, but the ground that those arguments are founded isn't entirely based on ignorance.
It's an extreme example of how what's legal and what's not can evolve over time.
Look at consent laws --- they didn't exist at all until about 740 years ago, and didn't really start to get age specific until 438 years ago, and even then it was an inconsistent target (and still is).
http://chnm.gmu.edu/cyh/teaching-modules/230
Marriage at 15 wasn't all that uncommon 150 years ago in the US, but is now pretty much a taboo.
If I'd have told someone 25 years ago that gay marriage would be recognized, they'd have laughed.
Laugh it off if you will, but I'd bet my next paycheck that there will be a legal challenge to polygamy within ten years.