The ancient origins of kissing

Hey, it's Hannah here, and this is What In The World, your podcast for the stories that get people talking from the BBC World Service. So think back. When was your first kiss? Mine was… A group of adolescent humans gather in the dimly lit basement of a coffee shop. This is their weekly after-school ritual. Though they're not here for sustenance, they haven't bought any coffee, but for something far more primal - connection. One teenager in school uniform approaches her chosen companion, they exchange words, and then it happens - a brief meeting of lips, an awkward, fleeting rite of passage. Then they're ejected by management to make space for paying customers. Now imagine if that moment had happened 21 million years ago. No basement, no school uniform, just a mouth collision between two big, hairy apes. Now I know why I wanted to kiss that guy, he was kind of cute, but we don't really know what was going on between the prehistoric apes, because there aren't any obvious survival or reproductive benefits to kissing. But scientists at Oxford University in the UK now think they've tracked down the beginning of mouth-on-mouth kissing. So forget every romantic Hollywood idea you've ever had about kissing, we're heading back to the start of this unexplained behaviour. Let's find out more about this now from our science correspondent, Victoria Gill, who is here in the studio with me, and I'm going to start by blowing you a kiss. That's so nice, Hannah. Back at you. So when was the first kiss? How have researchers been trying to answer that question? So they've answered this in kind of an evolutionary way, which is why they were looking at lots of different species kissing. To begin with, they had to look across the animal kingdom at sort of where kissing happens and then work out the kind of evolutionary relationships between those animals, to sort of track it back through time and evolution, to work out how old kissing is in our kind of biological history. So that's where looking at and gathering evidence of lots of different species kissing comes into this. And to do that, they had to define the kiss so that they knew that they were comparing the same behaviour. So they defined it in this really unromantic way where they, I think they describe it as oral to oral contact with some movement of lips or mouth parts and no food transfer. So that's what we have, the kind of biological definition of a kiss. And essentially, they looked at species that there's documented evidence of them kissing. They also looked at YouTube videos of animals kissing to sort of find out which species exactly indulge in this mouth to mouth contact. And they worked out the evolutionary relationships between them and they worked out in particular that lots and lots of primates kiss, lots of monkeys kiss, lots of great apes kiss. And so essentially, if the great apes kiss and we kiss as humans kiss, then the last shared ancestor between those great apes and us humans would probably also have kissed. And the last shared ancestor was around 21 million years ago. So that's how we get to this date of the first kiss emerging in our behaviour 21 and a half million years ago. It is quite romantic, I have to say. So you said it's not just monkeys, it's not just ape-like animals, what about the other species that kiss? Well, it's funny because there are behaviours that look like kissing, which is why they had to kind of define it in this way. So it has to be this positive interaction, it has to be this mouth to mouth contact. It's not like birds feeding worms to their young or anything. Exactly. Yeah, that's why they talk about no food transfer, because if you look at things like parent animals chewing up like pre-chewing food and then feeding it to their young, that looks like a lot like kissing, there's a lot of mouth to mouth contact there. So when they look across the animal kingdom and they looked at both the scientific literature and they see it on YouTube when people film animals in prairie dogs, in some birds, in wolves. They've even seen it in some zoo polar bears, and that was really quite sloppy, involving a lot of tongue. Oh no. I'm told by polar bear experts that that's pretty unusual, but yeah, lots of species seem to kiss each other. So tell me more about the research. So this was led by a researcher called Matilda Brindle at the University of Oxford, and her and her colleagues essentially just trawled through the literature to try and figure out this puzzle. What they really want to know is why we kiss, and it's really significant in terms of why this is so puzzling, right? So there isn't an obvious advantage to kissing. There isn't a reproductive advantage. It's not going to make you have more offspring that share your genes. There's not a survival advantage. In fact, there's some risks, right? If you're kind of mouth to mouth with another individual, there's a lot of microbe transfer. Like glandular fever, the kissing, so-called kissing disease. Exactly. So that's why they asked that question, because there are some risks involved. And answering this question, they've not quite got to the nub of why we kiss and why kissing involved, but they have answered the question of when it emerged that it's this ancient kind of evolutionary route that connects us with other particularly primate species and great apes. So that kind of suggests that there's something significant about kissing. It's important, you know, and we know it's important to us culturally and socially, right? If you think of all of the cultures, like not all human cultures kiss, if you think of, you know, the classic kind of cinematic ending to a romantic film, it's the kiss, right? It's so socially important to us. So what they're trying to get to the nub of and what they're trying to open up with this study is answering the question of the biology of why, right? Like why this has become such a significant part of our behavior, of our social interactions, but of other animals too. Could it be because it feels so good, doesn't it, to be in that close proximity with someone? But also, I always thought it was a lot of it was about smell, because when you're up close kissing someone, you can smell their breath, but you can also smell the scent of their body and whether you're attracted to that or not, is that one of the reasons we kiss? Well, there's a lot of theories out there about it that kind of are looking at exactly that. So whether that's something that we can take clues about sort of how kissing feels and the cues that get exchanged and how we can kind of sniff and smell each other and kind of be close to each other. Whether that's something that's such an important part of partnering up and of bonding, because what we do know is like social bonds between primates, including humans, you know, we're another primate, we're another animal, and our social bonds are so important, you know, for our survival. And they're important in the animal kingdom as well. If you look at social groups of great apes, of chimpanzees and gorillas, for example, those close knit social bonds, they're very protective, they help individuals raise their young to survive, to get food, to help each other through life. So it's clearly very significant. The other theory or one of the other theories is that it emerged from our sort of ape roots, from our ape ancestors, that it was a grooming and bonding thing that turned into and evolved into kissing. But there's lots of theories out there. What we do know is that it's an incredibly important part of our sort of social and cultural repertoire. It totally is. And talking about romance, can animals be in love as well? Can kissing be romantic between animals or are we just projecting human ideas onto them, which is why, you know, it's so cute to see gorillas kissing, maybe cuter to see gorillas kissing than a couple kissing on the underground. You know, that's such an interesting question. So I think we can't get away from it. I think Hannah, it's one of the reasons we're talking about this story, right? Because it's something that we feel such a close association with and we're so interested in. The idea that this very kind of human romantic behavior is something that's sort of shared across the animal kingdom. It's sort of lovely. It's adorable. And whether animals fall in love, it's that, again, is like an even bigger question that applies like individually to like lots and lots of different species. And it depends what we mean by that question, right? It comes back to that definition of like, what is a kiss? When you're looking at the biology of like mouth on mouth kissing, you have to define it in this really scientific, unromantic way. So do you mean can animals bond forever or does it mean something very human about that kind of falling in love, that being absolutely overwhelmed and obsessed by one or the other individual? I think we can really answer that question, but we can look at the bonds and the behavior between these animals by watching how they connect with each other and watching their societies to see what those bonds and what love and what kissing actually means to them. And kissing, it doesn't always have to be romantic. It can be platonic, like kissing a friend on the cheek or you know, some families, the parents kiss their kids on the lips and that must happen in the animal world too. Yeah, yeah, absolutely. And that's something that this whole scope of looking at actually when that arose, that included all of those just, you know, affiliative, affectionate, parent to infant, friend to friend, platonic kissing, you know, kissing between just individuals who were not partnered up in a reproductive sense. So yeah, it's absolutely, this is trying to get to the root of something that isn't just romantic, that is, you know, every kind of definition of the kiss, the mouth on mouth kiss. I have got this lovely warm fuzzy feeling, so thank you so much. You're very welcome. My pleasure. Well, that does make my teenage basement moment feel slightly less embarrassing. And if you've ever been worried about your kissing technique, just remember, you're fine. We've had 21 million years of evolution to work on it. Now before I go, we have got two updates for you. First, if you watched or listened to yesterday's episode on Miss Universe, we've now got a winner. Miss Mexico, Fatima Bosch has been crowned Miss Universe, and that brings an end to a pageant season that has been full of scandals. One of those scandals involved her being publicly told off at a pre-pageant event, and that led to a group of beauty queens walking out. Her victory has been celebrated by many Mexicans, as well as lots of others who applauded her walkout. And you may also have noticed that we have been bringing you daily updates from the COP 30 climate conference in Brazil. This is what happened there on Thursday. The fire has broken out within the compounds of COP. There's a huge panic. People have been running out of here. Huge columns of smoke rising up into the air. That's Justin Rolat. He is the BBC's climate editor. The venue hosting the talks caught fire. Several people were treated for smoke inhalation. On Friday was meant to be the last day of this year's summit. The talks were in their final stages, and now there are likely to be delays. But you can follow what's happening on the BBC News website, and we've also been posting about it on our Instagram @bbcwattintheworld. So come say hi, and if you're not already, you can follow us there too. That's it from me today. Thank you for joining us. I'm Hannah. This is What in the World from the BBC World Service, and I'll see you soon.