This question was explored by researchers at University of Wisconsin-Eau Claire, whose findings were published in the Journal of Social and Personal Relationships in 2012.

The researchers brought together 88 cross-sex friendship pairs and surveyed their level of attraction for one another. Participants were asked to self-report their attraction to their friend, estimate their friend's attraction to themselves, self-report their desire to date their friend, and estimate their friend’s desire to date them.

The results determined that men tend to have greater physical-sexual attraction to their cross-sex friends compared to women. Men were also found to overestimate their friends’ attraction to them. 

Yikes.

However, according to the paper, this relationship might have a deep basis in evolutionary psychology. The paper proposes that “men’s and women’s perceptions of their cross-sex friends are a manifestation of evolved human mating adaptations operating in a modern environment.”

In order to fully understand the data and hopefully get an answer to my initial question, I reached out to the author, Dr. April Bleske-Rechek. 

One of the first things she told me about the study is that there were two parts that didn’t make it into the journal. One of these additional studies sought to survey what individuals in cross-sex friendships tend to deceive their friends about. 

Perhaps not-so-surprisingly, Bleske-Rechek said the study found that individuals tend to deceive their friends about their sexual relationships with others. 

And in the fourth study, people in both current and terminated cross-sex friendships reported having romantic encounters with that friend, Bleske-Rechek said. In other words, romantic encounters were just as common in current cross-sex friendships as they were in terminated cross-sex friendships. 

According to Bleske-Rechek, however, those last two studies were omitted from the final paper because a reviewer didn’t like thinking about cross-sex friendships in the context of an evolutionary perspective.

However, in her opinion, humans are hard to understand without thinking about them from an evolutionary perspective, and including the article in an evolutionary journal would only be stating the obvious, so she sought to have it published in a more mainstream journal.

And to me, this makes sense. We don’t have to just consider evolution when thinking about how we behave (after all, we’re not animals), but we should definitely take it into account. 

Furthermore, another study conducted by Blseke-Rechek in 2016 had participants write down the name of a member of the opposite sex who wasn’t a romantic partner or family member. They then asked the participants who this person was to them, a friend or someone they’re attracted to. 

The findings, again, found that men were more likely to include somebody that could be a sexual partner.

In conclusion, Bleske-Rechek said she would never say that men and women can’t be friends. However, she said that it certainly is hard, as forming platonic cross-sex friendships is “not how we spent a long span of evolutionary history.”

Additionally, Bleske-Rechek’s study included other findings, such as the idea that “some people view sexual attraction as an important reason for initiating a cross-sex friendship” and the fact that half of young men and women have had sexual intercourse with a cross-sex friend.

While I find Bleske-Rechek’s work extremely insightful, science's jurisdiction seems to end with what can be proven with facts. 

So, I sought to conduct a survey of MSU students to see if their reactions would line up with Bleske-Rechek’s findings. 

My survey consisted of similar questions to Bleske-Rechek’s, asking students whether or not they thought men and women could be friends, whether or not they’re romantically interested in their friends, and whether or not they think their friends are romantically interested in them.

To my surprise, out of twelve students (six identifying as men and six identifying as women), all of them said that men and women can be friends, they don’t have romantic feelings for their friends and their friends do not have romantic feelings for them.

So either MSU students have mature friendships, or students didn’t trust me enough to be honest about their friendships. Whatever the case, the rest of my investigation into the question had to be answered with my own experience. 

And between Bleske-Rechek’s research and my own personal experience, I’ve seen two ideas emerge: men are more likely to introduce sex into a platonic relationship, and because one person in a relationship experiences some form of attraction, then the relationship is automatically null.

I’ll return to the former statement, but I want to address the latter statement, because while I can see the logic behind this conclusion, I also find it to be naive.

Don’t get me wrong, if a clear boundary is established between two friends and one friend continues to cross that boundary, then the friendship is likely null. But my interpretation of Bleske-Rechek’s research says that, due to thousands of years of evolution, romantic thoughts involving people of the gender you’re attracted to are inevitable. And preventing thoughts associated with thousands of years of evolution would probably prove impossible for most people. Because the fact is: humans do not always control their thoughts. 

Preventing actions, on the other hand, should prove to be less of a challenge.

And this is where the former statement (as well as some personal experience) comes in. Because too often I find that men will make the jump from “I have unfriendly thoughts/feelings for this person” to “this friendship has to be romantic,” when that doesn’t have to be the case.

Obviously, if someone has a genuine desire to date someone then they should (I’m rooting for you) but there are a thousand factors that go into making a friendship, and whether or not someone has had romantic thoughts about their friend is not the only thing.

When a cross-sex friendship goes null, it’s due to romantic actions, not romantic thoughts.

So to answer the burning question, yes, men and women can be friends. But it’s just that. They can.

It really is just up to the individual. It takes work on both sides, and perhaps more-so by men — whose socialization through patriarchy may affect their perceived lack of need to control their actions, sense of entitlement to women, and skewed perception of relationships with women. 

Harry’s argument in the movie is that “the sex stuff always gets in the way,” which I would say, yes, it can. However, if two emotionally mature, cisgender, heterosexual individuals belonging to the opposite sex are friends, then their ability to observe romantic thoughts as an inevitable fact of life and not act on them demonstrates a stronger devotion to that friendship.