Shan Boodram: My first crush was my neighbour, Devin, who aside from once participating in a "Shan Boooooo" chant, I'm not sure knew who I was. 

But despite that small detail, I genuinely believed we were made for each other. 

And that crush was followed by a cascade of crushes.

When I was a preteen, I used to serenade the boy band posters on my walls. You could say I was boy-obsessed. 

But why is that? Why have I always been into guys instead of girls? And why are some people into both, or neither? And why does it even matter?

Hi! I'm Shan Boooooodram, and this is Crash Course: Sex Ed. 

[Theme music]

When I talk about the people that we're into, I'm talking about sexual orientation — if men, women, neither, or both make you weak in the knees. 

Sexual orientation might line up with who someone's actually having sex with, or how they publicly identify, or it might not, for lots of reasons. We talked about that more in episode 1.

For now, though, here's the big thing to know: Sexual orientation exists on a spectrum — not just two opposites, but all possibilities in-between. 

So, on one end of the spectrum, if you're straight, that means you're a woman who's exclusively attracted to men, or a man who’s exclusively attracted to women. It's the same as being heterosexual, the prefix "hetero" meaning "other."

Now, on the other end, if you're lesbian or gay, you're a woman who's exclusively attracted to women, or a man who’s exclusively attracted to men. Both can be considered homosexual, the prefix "homo" meaning "same"—although that term can be seen as dated. 

But there are tons of other sexual identities in-between those two, often lumped together under the "LGBTQIA+" umbrella. 

Teen Shan: Should I say all the letters one by one like that? Or should I pronounce it like eljibbitycueaiah?

Shan: Definitely one by one. 

We're gonna get into that acronym a bit later, because it hasn't been around forever. 

But when it comes to all the variation in human sexuality? That's been documented for centuries. 

Diversity in sexuality was the norm in various cultures across the ancient world, from China to Egypt to Rome. Alexander the Great famously had both male and female lovers. 

But right now, it's illegal to be gay in 64 countries, and in 12 of those, it's punishable by life in prison or even death. And even in countries where being gay is legal, like the US, it's not universally accepted.

So what happened?

Well, different prejudices around same-sex intercourse have existed for ages, driven by religion and cultural beliefs. 

But the fire really sparked soon after Christianity came to ancient Rome, thanks to scripture prohibiting it. 

And in the 1200s, Christian philosopher Thomas Aquinas fanned the flames, claiming that same-sex intercourse was against the natural order of things God had created. 

This idea that homosexual behaviour is "unnatural" spread even further as a result of Christian missionary work and European colonisation. And it's been doing damage for more than 800 years. 

Like, flash forward to the 1950s, when the Diagnostic and Statistical Manual of Medical Disorders, the guide psychiatrists use to make diagnoses, was first published. 

It didn't call homosexuality a sin, but it did carry on the prejudices of the past by classifying it as a mental illness. 

It took decades for that classification to be undone, thanks to a psychiatrist in disguise  

Teen Shan, let em know. 

The year was 1972. Members of the American Psychiatric Association had gathered for their annual conference in Dallas, Texas. 

Several people sat on a panel about psychiatry and homosexuality... including someone wearing a costume and a Richard Nixon mask: Dr. Anonymous. 

"I am a homosexual," he said into a microphone that distorted his voice. "I am a psychiatrist." 

Leading up to the conference, lesbian activists Kay Tobin Lahusen and Barbara Gittings had searched endlessly for a gay psychiatrist who'd be willing to speak on the panel to help destigmatise their own sexuality. But doing so could jeopardise their careers, so many turned them down. 

Except for Dr. John Fryer, a gay psychiatrist who had lost a residency position because of his sexual orientation. He agreed to be the voice of gay psychiatrists on the panel — if he could protect his identity. 

During his speech, he spoke directly to the closeted psychiatrists in the room, saying that though coming out would be risky, "We are taking an even bigger risk... not accepting fully our own humanity, with all the lessons it has to teach all the other humans around us."

His speech made made an impact: the following year, homosexuality was removed as a mental illness from the DSM. And 20 years later, Dr. Fryer revealed himself as Dr. Anonymous. 

So homosexuality is not a mental illness. But that still doesn't answer our big question: why do we like who we like? Is it because we're born this way? Is there a code in my DNA that made me so boy-obsessed? 

Well, its not as simple as that, but scientists have found evidence that DNA and sexual orientation seem to be related.

They can't say that DNA causes anyone to be gay, straight, or anything else — but some studies have found evidence that there is a connection. 

Like, studies that followed identical twins found that if one twin was gay, there was a small increased likelihood that the other twin was as well. 

And big picture, a 2019 study found that hundreds or even thousands of genes may contribute to a person's sexual orientation, and which of those genes gets turned on or off is probably strongly influenced by internal factors, like hormones we're exposed to — not just in the womb ,but also later during puberty. 

So, biology might be part of the story. But it's also more complicated than Lady Gaga's Born This Way. 

One thing we know, thanks to sexological research, is that who we're attracted to isn't always fixed. 

This is called sexual fluidity, and it means that if you're attracted to one gender now, it doesn't mean you could never be attracted to another gender in the future. 

And surveys have found that those shifts might happen for various personal, social, or environmental reasons that aren't related to genetics. 

That said, evidence shows that sexual orientation can't be forcibly changed.

Notably, thousands of young LGBTQ+ people have undergone conversion therapy: treatments to try and make them heterosexual. This can involve medication, talk therapy, humiliation, and much more. 

But conversion therapy has been renounced by a long list of medical and psychological associations, including the American Psychiatric Association and the American Medical Association — not only because it's ineffective, but because multiple studies have found that it's associated with mental health risks. 

Ultimately, why we like who we like is complicated. Throughout the centuries, the way some societies have viewed sexual orientation has changed. And so have the ways people have talked about it. 

Which brings us back to that big ol' acronym from the beginning. 

It started with LG — the lesbian and gay community — but has expanded over the years, with different identities being acknowledged.

The B stands for bisexual. 

Teen Shan: I know what that means. It's being attracted to girls and guys. 

Shan: Well, yes and no. 

Some people see it that way, but others see bisexuality as encompassing more than the gender binary, including attraction to nonbinary and trans people.

And other folks choose to identify as pan or omnisexual, "pan" and "omni" meaning "all." 

The T and I are for "transgender" and "intersex", which we talked about in episode 4.

The Q has two meanings: "questioning," which helps those who may not be sure of their sexualities feel welcome in the group. And "queer," which is often used as a catch-all for the whole community, or as a way of not strictly labelling someone's sexual orientation. 

Teen Shan: Uh, Shan... even I know that word's not cool to say. 

Shan: Well, good point— "queer" has been used as a slur in the past, though today, many in the community have reclaimed it as a term for self-identity. 

But that isn't true everywhere, so be careful about using the term, especially if you don’t identify that way yourself. 

The A stands for asexual. This term encompasses the ace spectrum, people who experience low or no sexual attraction. 

For example, demisexual people only experience sexual attraction if they're already very close with a person. 

And finally, you've got the plus, which includes all the many additional sexual orientations people experience, and the words they use to describe them. 

Now, this acronym isn't perfect. Some folks think it's too clunky, or that it normalise straightness by lumping all the "other" people into one big group. 

But lots of people find it useful for building community, especially when they're fighting oppression and injustice against different marginalised identities. 

As for how many people are in this big ol' group? As of 2021, based on census data, the Human Rights Campaign estimated that there may be as many as 20 million LGBTQ+ adults in the United States alone. 

So yeah, that's why pride parades are so lit. 

In the end, we might not know exactly why we're into the people we're into — but as a society, we've definitely decided that it matters. 

Once, people wrote the story that being anything other than straight is wrong, and today, many others are working hard to unwrite it. 

Because variation in sexual orientation and behaviour has always been around. And our understanding of it will just keep on growing and evolving as we do. 

Next time, we're asking another big question: Is virginity even a thing? We'll see you then. 

This episode of Crash Course: Sex Ed was produced in partnership with the Kinsey Institute at Indiana University. If you're interested in learning more, visit their website for resources that explore the topics we discussed in the video today. 

Thanks for watching this episode, which was filmed at our studio in Indianapolis, and was made with the help of these fabulous people. If you want to help keep Crash Course free for everyone forever, you can join our community on Patreon.