Editor's note: Nicholas L. Syrett is associate professor of history at the University of Northern Colorado and the author of "The Company He Keeps: A History of White College Fraternities." The opinions expressed in this commentary are solely those of the author.

(CNN) -- In curbing the excesses and occasional crimes of fraternities and sororities, universities have relied on a traditional set of punishments. They have suspended chapters, or in extreme cases, expelled them from campus. And they have denied chapters "official" recognition as campus organizations. These strategies rarely have any lasting effect and they ignore two of fraternities' defining characteristics, both of which contribute to frequent misbehavior: exclusivity and gender segregation.

By mandating this week that its two residential fraternities admit women on an equal basis, Wesleyan University has taken an important step toward attacking the root of the fraternity problem.

At the risk of stating the obvious, the male-only policy is the heart of the fraternity experience. To the men who join them, it is fundamentally important that theirs is an all-male organization, a brotherhood. A fraternity allows a man to surround himself with others who confirm his masculinity.

It is no surprise that Wesleyan's decision has already been criticized by Delta Kappa Epsilon, one of its fraternities. No doubt many alumni are also upset. But gender exclusivity is precisely the problem with fraternities. In only allowing men to join, fraternities insist that men are fundamentally different from women right in the middle of an environment -- a university -- whose goal is to question such shopworn truisms.

Candidates for membership are evaluated not on a particular skill (like the ability to play soccer or engage in parliamentary debate) or welcomed not because they share political ideals or religious beliefs (like being a libertarian or practicing Catholicism). Rather, the primary criterion for membership—in addition to the secondary characteristics of good looks, wealth, coolness, athletic prowess and unofficially in some organizations, whiteness or blackness—is simply being male.

Fraternities' gender exclusivity has the effect of emphasizing brothers' collective traits, masculinity especially, above all others. Men who join fraternities understand that fraternity membership brings popularity and that their brothers will reward them when they "score" with women.

The reports of sexual assault and gang rape associated with fraternities have much more to do with this kind of hyper-masculinity than with the binge drinking that is so frequently blamed. Men rape women because they believe they are entitled and because they think they can get away with it.

There is an obvious chicken-and-egg question here: Do young men who think about women in demeaning ways join fraternities because the organizations validate their thinking? Or do fraternities inculcate these attitudes in their members? The answer is: both.

Wesleyan's new policy will force fraternity brothers to interact with their female peers in something much closer to equality than before. They might even find that they have something in common. And this sense of similarity might also lead them not to countenance the kind of rapes that occurred in their houses in 2010 and 2013, and that (along with the resulting lawsuits) are surely the impetus behind this step by Wesleyan's administrators.

Wesleyan is only one school and it only has two residential fraternities. It has not mandated gender inclusivity in the organizations (including its one sorority) that do not have on-campus housing. And there is no reason to think that the new policy will lessen drinking, another perennial problem associated with fraternities.

But it may well go some way toward making Wesleyan fraternity men see their female classmates as something other than a proverbial notch on a bedpost. After all, they will now be sisters.

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