“Girls mature sooner than boys.” I’ve got a twin brother, so I heard this even more than most kids, and most kids hear it a lot. It’s the explanation for why girls paint each other’s toenails at slumber parties and boys try to burp the alphabet. It’s the reason parents trust 14-year-old girls to babysit their five-year-old kid. It’s why we’re not creeped out when an 18-year-old girl dates a 25-year-old guy. They may be seven years apart in experience, but emotionally they’re equally mature. 

What constitutes maturity? I matured dentally very early. I got my wisdom teeth out when I was 15, which I think is interesting, but you probably don’t. Nobody cares how fast people lose their baby teeth. The maturity we’re talking about is the ability to handle responsibility. It’s doing what you say you’re going to do. It’s judging social situations and behaving appropriately in the context. It’s adhering to social norms. It’s not finding fart jokes funny. 
We talk about social constructs a lot here. Social construction might be in the drawer of things you’re tired of hearing about, nestled between “problematic” and “appropriation.” Sorry! Often we call something a social construct in order to dismiss it. “What are job applications, anyway? Employment is a social construct. Hahaha!” 

This is silly because understanding social construction is really important. Calling gender a social construct means that it is something that we as a society make collectively, not something that “just is.” One of the ways we make gender is by telling and believing myths about how it “just is” that “girls just mature faster than boys.” From a constructivist perspective, it’s wrong because it relates maturity to biological characteristics. That’s enough. 
But that’s not enough for the world outside of academic feminism. It matters for the rest of us because it’s a myth that serves patriarchy (I know, again with the patriarchy!). To be clear, I mean something specific by patriarchy. It’s a system in which men, particularly old men, have economic and political power over everyone else. 

The myth that girls mature faster than boys serves patriarchy in (at least) two ways. First, it justifies romantic relationships between older men and younger women in which there is a substantial power gap (see my column on relationships between upper- and underclass students). And second, it excuses hurtful or irresponsible behavior in men but not in women.
 The flipside of the first consequence is that we expect behavior of girls that we don’t expect of boys. Believing that girls become women earlier than boys become men is a way of justifying how much we ask of them. Emotional labor, or all of the “feelings” work that women do and men don’t (remembering birthdays, sending get-well-soon cards, giving emotional support), is an idea that’s gotten a lot of traction in the pop-feminist community recently. The teacher’s pets, the helpful daughters, the obliging sisters, they’re all doing work. Labor. And after a lifetime—or just an adolescence—it’s draining.

 Somehow this maturity difference is still a thing that otherwise progressive people believe about gender. All too often I find myself nodding along, not sure how to suggest that I see things a little differently. So here it is: the belief that girls mature faster than boys is untrue, sexist and harmful.

 My twin brother is more mature than I am by many counts. He works full-time, has bills and rent to pay and cooks all his meals. He thinks about health insurance and helping our dad around the house. Just because he’s a boy doesn’t mean he’s any less mature than I am—in fact, in some ways, he’s more mature. This goes to show, our maturity is developed by our social world, not determined by our gender—even though I did get my wisdom teeth out when I was 15.