Revisited: the endless sexual diversity of nature
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This is The Guardian. Hi, Ian here. The Science Weekly team are taking a break, so we're bringing you some of our favourite episodes from 2024. Back in June, some new research showed that same-sex sexual behaviour in animals is often witnessed by scientists but rarely written up. And that got us wondering, how common is this behaviour in the animal kingdom? It was fascinating to learn just how varied same-sex behaviour in animals can be.

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In 1910, Robert Scott and his fellow explorers set off across the ice fields of Antarctica on their fateful mission to conquer the South Pole. The tragic expedition went down in history, but what's less well known is another story which began on that trip and only emerged a century later. On that expedition was the ship's surgeon, a man called George Murray Levick, and as was common for that time, Levick was also the ship's naturalist and photographer.

Josh Davis is a science writer at the Natural History Museum in London. And while Scott went off on his expedition to the South Pole, Levick and a few other men basically spent 11 months at a place called Cape Adair where they have what is the largest breeding colony of Adelie penguins. Levick was the first scientist to witness and record the entire breeding cycle of the Adelie penguins.

and whilst he was observing these behaviours, he sort of saw some behaviours, some activity that he basically couldn't really understand. This included things like forced copulation, necrophilia, and also homosexual behaviours.

Levick was presumably so confused and maybe sort of to a certain extent disturbed, I guess, about these behaviours that he wrote some of the observations up in a Greek cipher. And I think the assumption here is so that sort of prying eyes wouldn't necessarily be able to read what he had seen and what he was observing. When Levick returned to the UK, he tried to publish his findings, including the sexual behaviour of the penguins.

But at that point, the section which he had written on the sexual activity, the sexual behaviour of the penguins, was excised by the then Keeper of Zoology at the Natural History Museum. And it wouldn't be until almost 100 years later, when a copy of this pamphlet was discovered sandwiched between two books at the Natural History Museum in Tring, that the sort of nature of this story was discovered, really. What I find really fascinating about this story is that it shows really clearly how

In certain cases, the history of homosexual behaviours is one which has been covered up, explained away or disparaged. Fast forward to 2024 and penguins have become well known for same-sex couplings. But a study published last month found that animal homosexual behaviour in primates and other mammals is still underreported by scientists. Widely observed, yes, but seldom published.

So today we're asking, why do we still treat same-sex sexual behaviour in animals as rare? And could correcting the record help our understanding of human sexuality? I'm The Guardian's Science Editor, Ian Sample, and this is Science Weekly.

I kept finding all these like fascinating and really interesting bits of information about behaviours and biologies that were often in disparate books, scientific publications or websites. And there was never seemingly one central source bringing it all together. That's where Josh's recent book, A Little Gay Natural History, comes in. And that was kind of my main motivation, I think, was to

sort of showcase the extraordinary diversity of the natural world when it comes to these sexual behaviours and biologies and sort of shout about them a bit more because they are genuinely amazing and genuinely interesting.

It's perhaps easier to understand why Levick's section on penguins was cut from his expedition report back in 1915. But why do you think there still remains this tendency for animal same-sex sexual behaviour to be underreported? It's a really good question. I think there's various different things at play here, most likely.

I think historically there has certainly been a fear, I think, particularly from younger early career researchers to publish on these behaviours because they're worried they might get associated with those behaviours. I think there's definitely reports of that happening probably around the sort of 60s, 70s, 80s.

I think in more recent times, it's a bit trickier. There's obviously a recent paper talking about how underreported homosexual behaviours were. And part of the reasoning behind that was the way that journal publishing models now work. They're less likely to publish on short observational behaviours, which I guess is what homosexual behaviours would probably fall under. So I think it's a combination of factors. And I think it has changed through time and over the last few hundred years.

Your book looks at a variety of sexual behaviours in the animal kingdom, whether that's pathogenesis or hermaphroditism. We're going to focus on the area that's caused probably the most controversy over the years, same-sex sexual behaviour. Just how common is it in the animal kingdom?

Same-sex sexual behaviour has been recorded sort of officially for, I think the figure which is normally used at the moment is about 1,500 species. But it comes from effectively the entire tree of life. So you've got everything from orb-weaved spiders and humboldt squids at one end to Ghanaian cock-of-the-rocks and Western Nolan gorillas at the other end.

So the fact that you're finding these behaviours on almost every branch of the evolutionary tree means that that 1500 figure is probably a gross underestimate of the number of species in which same-sex behaviour is observed. The earliest example in your book is about this brilliantly named cockchafer beetle species.

Tell me about that story. How did the scientists make sense of what they were seeing in that study? Yeah, so this story started in, I think it's about 1834, when researchers discovered two male cockchafer beetles having penchant of sex.

And it resulted in this rather extraordinary drawing by a man called August Kelch in 1896. And this is thought to be the first ever drawing of non-humans, same-sex sexual activity. And he very vociferously argued, actually, that some of these beetles were actually engaging in the sex out of preference. And it spurred quite...

a long heated debate amongst entomologists on the continent about the nature of what they were seeing. And what is really interesting about this study is not only were they trying to explain the behaviour away, so for example some people were suggesting that maybe one of the beetles was blind or quite often you get what is called, I think it's called the prison hypothesis in which you have lots of males in a single environment and therefore they have to have sex with each other.

What I find more interesting about this and this debate is that very quickly it starts to almost be a cover for talking about human behaviours. So if you look at the language being used, they'll talk about active and passive partners, for example. And so it seems that they were using these beetles as a... basically as a proxy to talking about human sexuality and particularly male-male sexuality. It is interesting looking at the language in that paper. I mean, there's this...

in there where it says that the larger and the stronger of the two had forced itself on the smaller and weaker male, had exhausted it, and only because of this dominance had conquered it. I mean, there's a lot of framing in those words. Yeah, and this is something which comes out again and again throughout all of these studies is the language being used is quite often moral language.

And even up until quite recently, so one of my favorites is, I say favorite in a very loose term. I mean, it's quite terrible when you look at it now, but it is funny, was in 1987, there was a paper titled, I think it's something along the lines of, on the lowering of the moral standards of the Lepidoptera.

Which is a butterfly. Which is a butterfly, yeah. So we're assuming that these butterflies have moral standards to start with, and that somehow sort of homosexual sex or queer sex is a lowering of those standards. And that's in the 80s, which I find extraordinary. Beyond those, beyond the Beatles, give me some of your other sort of favourite examples of same-sex sexual behaviour in the book. Go on.

Gosh, where do we start? One of my favourites is probably dolphins. So they're quite frequently engaged in homosexual behaviour. But then it also occurs within female dolphins as well. And there's a really fun behaviour in spinner dolphins in which they quite often insert, for example, their fins or their dorsal fin or their pectoral fin into the other female's vaginal opening and stimulate her that way.

But then they will also sometimes put their snout into the vaginal opening. And then because obviously dolphins can echolocate, they will buzz their snout. And what can only presumably be, you know, to cause pleasure to the female, because it turns out that dolphins also have like really massive clitorises as well. So there's presumably a lot of pleasure going on and a lot of engagement there. The behaviour is known really rather earnestly in scientific literature as beak genital propulsion. Propulsion. Yeah, I know.

There are countless examples of animals engaging in same-sex activity, but I guess there's this question of why. I mean, some people listening might be thinking here of our Darwinian paradox idea, you know, if there's no chance of these animals producing offspring, what's the point of them having the same-sex sexual behavior? Is that just looking at it completely the wrong way?

I think so. I think that's a really outdated way of looking at things. I think that that is probably historically what was thought, but that is also predicated on the idea that the only purpose of sex is reproduction. And we know that that is clearly not the case. I think there's now a greater understanding that there are a lot of different roles that sex can play within societies and with communities of animals, be it, you know, social bonding or stress release or even just pure pleasure, as I'm sure those dolphins know quite well.

Do you think there are other advantages of these same-sex behaviours going on? I think there are some clear advantages, particularly within species that have been well studied. So, for example, bonobos engage in a lot of homosexual behaviour, both male-male and female-female. And I think a lot of studies that have looked into this have shown that quite a lot of that behaviour is to do with social cohesion. So it's about diffusing situations, for example, and stress release and social bonds amongst the apes.

There are other examples which show how same-sex behaviours can actually be advantageous. So a great example is the black swan from Australasia. And around, I think at any one time, around 20% of all black swan couples are male-male couples. And what's super interesting about that is that those male-male couples are able to maintain larger territories than the male-female heterosexual couples.

And partly as a result of that, they're able to raise more chicks successfully to fledglings. And another reason they think is that because the male-male pairs basically share the incubation and the egg duties more equitably than the male-female, where the female is the predominant one to sit on the eggs. Up until now, we've been talking about same-sex sexual behaviour, but...

I wonder if it's possible to actually talk about sexuality among animals. I mean, you can't go up to an animal and ask their sexual preferences. Has science found an answer to this? This is one of those really critical questions when we're talking about sort of queer natural history, right? We can't ask animals, unfortunately, if they're gay. It'd be really, really helpful if we could, but that's not possible. But there are a few examples where scientists have basically come close to answering that question as best they can.

The most obvious of these is actually the domestic sheep. And I really love that it's just like the humble sheep that is answering these questions. We've observed their behavior for a long time and we can actually sort of do some of these experiments on them. So they've done experiments in which they've given rams the option to mate with another ram or a ewe in heat. And for about 8% of all rams, they will preferentially choose the other male to mate with rather than the ewe. And they maintain that preference over time, which I think is the critical aspect of this.

So we can go somewhere closer to say that about 8% of all rams are probably gay, but again with the really heavy caveat that we can't actually ask them, so we can't say that for certain, which is one of the main issues with this biology of these questions, I guess. That takes us on to us humans, because of course all of this is being viewed through our own anthropomorphised understanding of sexuality, and that can obviously bring us some challenges.

We heard about how controversial examples like the penguins and the cockchafers were over a century ago. But even in living memory, scientists trying to report on their findings have found themselves embroiled in culture wars. Tell me about the case of the lesbian seagulls. They seem quite prominent in this story.

So in the 1970s, there was a, it was actually a husband-wife partnering and they were studying Western gulls off the coast of California. And they started noticing something unusual about the pairings. They noticed that some of the nests had more eggs than would be typical for this species of gull.

And when they finally were able to ascertain what was going on, they found out that the gulls with the larger clutches were two females. Well, they were termed at the time lesbian gulls, but again, we can't necessarily be certain about that.

And what is so fascinating about this example is that it landed sort of right in the middle of the time of that sort of queer revolution in the US. And it was sort of embroiled with all of these conversations about the nature of homosexuality. And because at that time, one of the sort of key arguments against homosexuality, particularly amongst the Christian and right in the US,

was that it was unnatural. It sort of exploded into this political landscape, I guess, to the extent that even in Washington, D.C., when they were debating the funding for these sorts of studies, it held that funding up for 10 days as they were sort of

why our money should be going to study what they were terming at the time these lesbian girls. And that study led to some songs, didn't it? Yeah, definitely. It led to a song called Lesbian Seagull. Because obviously, why not?

And so let's fast forward to today, Josh. I mean, when you were writing your book, did you experience any pushback on this? I have had, particularly on social media, a fair bit of pushback in the past. They frame it in the, I don't know if you know of the naturalistic fallacy of just because it occurs in nature doesn't mean that it should or it's morally occurring in humans. So, for example, quite often they'll be like, oh, well, some animals engage in cannibalism or infanticide. That doesn't mean that humans should be doing it as well.

Up until about probably the 1970s, as we talked about, the argument against homosexuality was that it doesn't occur in nature, therefore humans shouldn't be doing it. And then all of this sort of reports and studies came out saying actually a whole variety of animals engage in homosexual behaviour.

And that kind of almost killed the argument off. And now I certainly feel within the last maybe 10 or so years, that has now been twisted again and has been turned on its head once more. And it's saying just because it occurs in nature, therefore it doesn't necessarily shouldn't occur in humans.

And I find that decision or that movement to twist that argument once more really interesting and quite insidious, actually, to be perfectly honest. I want to take that on a bit more because clearly there's a lesson here in not viewing the animal kingdom from the perspective of human politics and sexuality. But do you think there's something to be gained by looking at humans from the perspective of the wider natural world? I mean, one which is clearly far more...

sexually diverse and interesting than a lot of people might think from what they've been reading because people aren't reporting it. Yeah, definitely. I think one of the key takeaways of my research in the book is that basically in nature, anything goes. There is no or very few, let's say, hard and fast rules within the natural world. And there's more often than not,

exception to any rule. And those rules that we put in place are quite often enforced or thought up by people. And nature is basically endlessly diverse from that point of view. And that's what I find so fascinating about it, is you find all these extraordinary edge cases where you're like, oh, actually nature isn't quite working in the way that we thought it should be working at this point. And then how does that actually influence

looking back at what we thought beforehand. And I think that is some of the most interesting parts of biology and some of the most interesting aspects of these behaviours. Josh, thanks for coming on. You're welcome. Thanks again to Josh Davis. His book, A Little Gay Natural History, is out now. And that's it for today. This episode was produced by Tom Glasser. The sound design was by Tony Onuchukwu. And the executive producer is Ellie Burey. We'll be back on Tuesday. See you then.

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