I see what you're saying, but you're missing my entire point of this whole conversation. I DO think legal thresholds are somewhat arbitrary and can't account for individuals, but I'm just saying that if we ARE going to set some kind of official definition of what it means to be grown, we might as well rely on scientific research and facts–which clearly demonstrate that brain development doesn't complete until a person is well into their 20s. Not some random age like 18.

Either way, regardless of when one becomes an adult, it still doesn't automatically make them innocent. If they're old enough to have a sex drive and initiate contact, then they're old enough to take responsibility for their actions. Yes, you could say they weren't old enough to fully comprehend all of the consequences that might come about as a result of that, but it still doesn't make them totally innocent victims. They know what the hell they're doing.