how did homosexuality evolve?

Hey guys, Tara here for Dnews - and over the past 2 years of doing this show,

we've covered a lot of scientific breakthroughs. Finding water on Mars, birth control for men, the relative usefulness of bras…

but now, science may have solved one of its greatest mysteries

yet: how did homosexuality evolve?

Well, according to new research published in the journal Archives of Sexual Behavior,

it may have evolved in order to promote social bonding amongst humans.

This is the first study of its kind to find discrete evidence that our need to bond with others,

actually increases our openness to engaging in homosexual behavior.

For their study, a team of researchers from the University of Portsmouth looked at the

relationship between sexual attitudes and the hormone progesterone.

What they discovered, is that the more progesterone there is in a heterosexual woman's saliva,

the more open she is to the idea of engaging in homosexual behavior.

Likewise, heterosexual men who are subtly reminded about the importance of having male comrades.

Reported feeling more open towards engaging in homosexual behaviour - and that was particularly true for men with

higher levels of progesterone.

But what is it about this hormone that relates to all of this? Well, a bit of background -

progesterone is a steroid hormone, typically found in women's ovaries and men's adrenal glands.

In the same way that oxytocin is considered to be the “love hormone”,

progesterone is basically the “friend” version of that.

It's one of the main hormones responsible for caring and friendly behavior, which is why your levels of progesterone tend to rise

when you're having a close interaction with a friend.

Obviously, from an evolutionary standpoint, it's beneficial for humans to form social bonds.

So from that perspective, more progesterone in your body is a good a thing.

But then comes the topic of reproduction - which for humans, is basically the logical endpoint

of sexual behavior. Or at least, we think it is.

According to lead author Diana Fleischman, sexual behavior hasn't always been just about reproducing,

it's also about forming and maintaining social bonds.

And there's certainly evidence in other species, demonstrating that recreational sex isn't limited to just humans.

Great apes, for example, have historically engaged in homosexual behavior as a way of forging new friendships.

While we are on the topic of forging friendships,

I wanna veer off for a minute and let you guys know that today will officially be my last day on Dnews.

For those of you who follow me on Twitter, this shouldn't come as too much of a surprise -

since I did announce a few weeks ago that I would be leaving Discovery at the end of November.

But I just wanna say, for the record, what an absolute pleasure it has been working on this show -

it has been such an amazing experience

getting to host what I consider to be one of the best YouTube channels out there - no bias obviously.

Not to mention, being able to work alongside such an amazingly talented team, both on-screen

and behind the scenes, has been very inspiring.

I specially wanna thank you guys, our viewers, for welcoming me onto the show and into your homes.

you guys have been so wonderful to me these

past 8 months, and I will forever cherish my time with Dnews.

Of course, if you would like to keep up with me outside of the show, I encourage you to

follow me on Twitter, at twitter.com/taralongest.

As always, if you guys have any questions, comments, fun memories, embarrassing moments

of me you'd like to reminisce about, please leave them in the comments below. Otherwise,

thanks for watching! I'll miss you guys.