Unraveling the Secrets of Cold Adaptation and Hybridization in Primates with Evolutionary Anthropologist Dr. Laura Buck

For this episode, I sat down in the studio with evolutionary anthropologist Dr. Laura Buck in the Research Centre for Evolutionary Anthropology and Palaeoecology of Liverpool John Moores University.

Dr. Susumu Tomiya of CICASP also joined the conversation.

After waxing on the plausibility that some ancient hominins in cold climates might have hibernated - spoiler alert! Not very - Laura describes the evolutionary and developmental processes that lead to adaptations and behavioral responses to the cold.

We talk about human cold adaptation and how they relate to those of Neanderthals, and how patterns emerge to help species thrive in thermally-inhospitable places.

Laura describes her current research, and how scientists might have overlooked a potentially critical evolutionary force among mammals: hybridisation.

We touch on the idea of genetic rescue for conservation, and whether the "grolar bear", a hybrid between grizzlies and polar bears, might - and that’s a controversial might! -  might allow polar bear genes to survive climate warming in the arctic.

Laura’s work on hybridisation has focused on macaques, but she argues that what we learn from studying hybrid macaque bones can help us understand many of the mysteries of evolution.

She touches on the modern techniques used in geometric morphometrics - simply put, measuring bones in cool ways to understand evolutionary processes - including the future role of AI in the process. 

Laura closes with the idea of niche construction, where it’s not only how we and other species adapt to the environments around us, but also how we change those environments ourselves, leading to the conclusion that in many ways we are responsible for our own environments of evolutionary adaptedness.

Other topics covered in the interview:

• Non-adaptationist explanations and just-so stories in human evolution
• Fieldwork fails with technology in scanning and measuring bones
• Nasal air conditioning
• climate adaptations comparing prehistoric humans in Japan with Japanese macaques
• Hybridization and evolution of the primate pelvis

As the Northern hemisphere gears up for the winter, remember that we all have some physical and many behavioral adaptations to the cold. 

But, if you’re unsure, hey, maybe you can just hibernate…

The PrimateCast is hosted and produced by Andrew MacIntosh. Artwork by Chris Martin. Music by Andre Goncalves. Credits by Kasia Majewski.

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A podcast from Kyoto University and CICASP.

Transcript

Andrew MacIntosh: 0:00

You're listening to the primate cast. After the tune, an interview with evolutionary anthropologist Dr Laura Buck on human and non-human primate cold adaptations, the process and outcomes of hybridization and modern tools that make meaning of the shape of bones. Hey everyone, and welcome back to the primate cast. I'm your host, andrew McIntosh of Kyo T University's Wildlife Research Center, and the podcast is brought to you by the Center for International Collaboration and Advanced Studies in Primatology at Kyo T University's Center for the Evolutionary Origins of Human Behavior. Now for this episode. I sat down in the studio with evolutionary anthropologist Dr Laura Buck of Liverpool John Morris University. Laura was visiting the institute to do some collaborative work on the post cranial skeletons of Japanese macaque and Taiwanese macaque hybrids. We were also joined in the studio by Dr Susumu Tomia, my good colleague here in PsyCASP, who dropped some great follow-up questions and color commentary. That really brings to the fore Laura's breadth and depth of knowledge about primate evolution. After waxing on the plausibility that some ancient hominins and cold climates were hibernators spoiler alert not very Laura describes the evolutionary and developmental processes that lead to adaptations and real-time responses to life in the colder climates of the world. We talk about human cold adaptations and how they relate to those of Neanderthals, but also how general patterns emerge to help species thrive in these thermally inhospitable places. Laura then describes her current research and how scientists might be overlooking a potentially critical evolutionary force, that being hybridization. We touch on the idea of genetic rescue for conservation, passing over whether the griller bear hybrid between grizzlies and polar bears that might, even though it's an extremely controversial idea that might allow polar bear genes to survive the pending environmental crisis facing the north in climate warming. But Laura's work on hybridization is mostly focused on macaques and she argues that the things we learn from studying hybrid macaque bones can help us understand many of the mysteries of evolution. After touching on the modern techniques used in evolutionary morphometrics simply put, measuring bones and cool ways to understand evolutionary processes, including the future role of AI, laura closes with the idea of niche construction, where it's not only how we and other species adapt to the environments around us, but also how we change those environments ourselves, leading to the conclusion that in many ways we, and especially humans, are responsible for our own environments of evolutionary adaptedness. So I learned a lot through this conversation and I'm happy to share it with you all here.

Andrew MacIntosh: 3:05

On the primate cast as the northern hemisphere gears up for the winter. Remember that we all do have some physical and many behavioral adaptations to the cold. But if you're unsure, hey, maybe you can just hibernate. Either way, here's our conversation with Dr Laura Buck to help get you prepared. Recently I've come to the conclusion that it's kind of fun to start each of these interviews with like a kind of off the wall question. So maybe the closest off the wall question I could think of when I was templating out this interview, laura, is do humans hibernate?

Laura Buck: 3:42

I would say probably not well currently, although teenagers sometimes might seem as though they do we don't?

Laura Buck: 3:49

I think the reason for this question comes from an article which came out a few years ago from a team who studies an amazing site called Atapueca. There's several different time periods at Atapueca which are important. The one which is in question is the Cimidolus huisos, so in this it's called the pit of bones in Spanish, and at this site there's hundreds of fossils which belong to just to quite a large group of people which is quite rare in the fossil record. So it's a very well studied, very famous site and some work came out a few years ago from one author who working with one of the Atapueca team, who suggested that the pattern of damage in the bones made it look like these hominins had been hibernating. They were alive about excuse me 400,000 years ago, so it's quite cold period and hibernation can be beneficial in that kind of situation. You know other animals do do it. Bears is the one that gets referred to a lot and the authors said that it looked like in the adolescence in particular there had been this pattern of damage to the bones, sort of metabolic issues, and then in the older individuals, healing after these periods of damage. So they attributed this to sort of seasonal insults to growth and sort of seasonal cessation of puberty. I have to say it's not something that seems to have been picked up by paleoarthopologists on a wider level. I had a quick look at it about six months ago when I was writing a popular article for the conversation about adaptation to the cold. It was during a very cold period in the British winter. So we're interested in how people adapt. It seems like there's just this one paper, it's a theory. There were probably other ways of explaining that damage and personally I think it's just not the most plausible explanation. One thing if it was such a beneficial thing to do, you'd expect other hominins to do it.

Laura Buck: 5:41

Neanderthals are the famously cold adapted hominin. Not to say that Neanderthals are exclusively cold adapted, but they definitely inhabited some cold periods. They're also this direct descendants. We think of these Atapuaca people. The Atapuaca people are often described as early Neanderthals, so they have a lot of those Neanderthal traits already. So if it was something that they were doing and that was working, you would expect to see Neanderthals do it.

Laura Buck: 6:06

I never heard anyone describe that pattern of bone damage in a Neanderthal assemblage and also we have evidence of hunting year-round in Neanderthal sites. So it doesn't seem like something they're doing. It's also pretty rare in large-bodied animals. I think there's a difference between different types of hybridization. Hibernation there's the one where you're sort of asleep for the entire winter and then bears and things which are large-bodied tend to go into torpor but they sort of wake up a little bit. But even then it's quite rare in large-bodied animals and it's not seen in any other primate that's a haplarine. So in our sort of large group of primates which might be partly because most primates don't have it a cold environment- but, it just seems like it would be a bolt from the blue, if you like.

Laura Buck: 6:49

It's not something we have an evolutionary history of doing. It's not something we have evolutionary evidence afterwards of doing, and if they were doing it, they were really bad at it. It seems to have done them a lot of damage, so I'm not convinced. Basically.

Andrew MacIntosh: 7:02

Yeah, I mean super interesting story. So what would be the other kinds of explanations that you could have for the observations that the scientific team made that led them to believe hybridation might be one of the explanations? So what was it specifically about the bones that they found?

Laura Buck: 7:17

It's sort of a seasonal pattern, so bones grow almost like tree rings. So you can sometimes see where the damage has happened in the sort of history of the bone. But they do remodel afterwards, which is why the main evidence was found in adolescence. They describe it, without getting too technical, sort of beyond my expertise and beyond probably people's interest. They describe it as looking like a rotten fence post. So it's sort of bone not growing normally and sort of resorption, so breaking down of bone where there shouldn't be. Some probably related to metabolic issues. I don't know enough about bone pathology, but they're talking about it in terms of a sort of periodic famine, which I can see how that would happen. So I don't see why seasonal scarcity in itself necessarily would imply hibernation. Something just not enough food in the winter period seems quite plausible without that necessarily being related to hibernation.

Andrew MacIntosh: 8:15

So you mentioned earlier, well, two, things that I want to pick up on in one of the second. One will go more into the the broader scope of this interview that I wanted to put together. But the first one is you said something interesting about this process of science. You said you were having in in Britain, I guess, a particularly cold winter. So people got interested in what people do when it's particularly cold and so hibernation one. But I wonder if you so that's kind of an interesting, I guess, the process behind science kind of thing. So do you have other examples of where maybe this is an off the wall question as well, and maybe it's even in your own process of how, like things that are happening now in our own kind of lives are kind of dictating the kinds of science that we're interested in doing?

Laura Buck: 8:58

The, the link between the cold winter and the hibernation paper was sort of the popular paper, so it was more that the popular website, the conversation suddenly thought, oh, people will be interested in that, it wasn't that. The research was done at that time. I think science takes like the actual research takes longer, so it's harder to be sort of on your toes and react to it like that. I think a lot of research has been done in response to COVID, like recently, for example, though like just our renewed appreciation of the effect that something like a pandemic has on people, I think has has sort of it's led to more funding and more sort of visibility of research on past diseases, but also probably more people considering the effect that disease has on the history of our evolution and, more recently, things like the Black Death, the effect on population demographics, things like that. So it definitely does happen, but it takes a few years to filter through.

Laura Buck: 9:52

I think An example of I can think of in my own sort of research, history is not something that happened in the sort of sense of something stochastic, but the publication of the Neanderthal genome in 2010, which was just not long after I'd started my PhD, probably led to my interest in hybridization Because in my undergraduate career up to that point the possibility of hybridization was generally played down. The main story was that there was this replacement of homo sapiens of other hominins out of Africa. Possibly there was some interbreeding, but it hadn't been important. It certainly wasn't expect to see this percentage of Neanderthal DNA in most non Sub-Saharan African people alive today. So that was a huge finding and I think that sort of. I didn't start working on things related to that immediately, but it bubbled along in the back of my, my imagination to what effect would this have hybridization have had? And then there's obviously a lot of research coming out in that area and it's sort of become this, this growth industry, if you like, in human evolution since those first papers have come out.

Andrew MacIntosh: 11:00

And also huge popular frenzy around it as well, with people 23 and me or other kind of genetic lineage stories of people figuring out how much of their DNA. Is that Neanderthal? So?

Laura Buck: 11:12

absolutely.

Andrew MacIntosh: 11:13

Yeah, definitely catches people's imagination. I definitely want to get into hybridization, but just to kind of follow up on this, you've mentioned Neanderthals now a couple of times and you talked about hibernation as maybe one of the more farfitched ways that people have adapted to living in colder climates. I think you mentioned in that conversation piece that we've kind of dominated the colder climates around the planet despite not really having any adaptations to it, and so what are maybe some of the other ways that humans, or even other species more generally, can adapt to cold climates?

Laura Buck: 11:48

I think all species do this to a certain extent, but humans are like the apotheosis of using different methods of adapting, in sort of layers of armor. So we tend to adapt behaviorally and culturally first. Then we might acclimatize, so short term adaptation. The next stage would be something like developmental plasticity, which thing stresses that you're exposed to when you're growing up, affect the way that you, your adaptation goes, and then sort of the last adaptation threshold, if you like, is this change generation over time. So humans definitely have all of those types of adaptation to cold. So the first thing you do if it's cold is you probably put on some clothes or you light a fire. You might migrate to somewhere that's warmer, if that's possible with where you're living Then. So those are all sort of they're easy because they don't really cost you very much. Okay, it might, depending on how you're making your clothing, if that might be something that takes a lot of sort of time and energy, but a behavioral option is usually reversible and it's usually less costly than adapting biologically. Then there are things like vasoconstriction, which is the blood going away from your extremities to avoid heat loss and to, yeah, to keep the most important parts of you war. So that's a sort of very short term option. Then there are sort of longer term things which might be more plastic, so things that might happen if you're exposed to cold stress from an early age. Things like the, the size and shape of your skeletons. So one of the two of the most famous rules to do with animal size and shape, including human size and shape of Bergman's and Alan's rules, and they're sort of taught at undergraduate level all in biology and anthropology all through the last well, 100 years or so at this point, this is the idea that if you're in a cold climate, you want to get as close to possible as being a sphere, because it has the least surface area, so you're losing the least heat, so you want to be bigger and you want to have less, sort of shorter arms and legs, shorter appendages. And humans do obey those rules to a certain extent. Research done longer ago before quite as much sort of gene flow between different populations and issues with obesity and things like that have a stronger pattern, but they do still hold, albeit more weekly today. So that's that does seem to be something that happens.

Laura Buck: 14:07

For example, if you take pigs and you raise them in a cold environment, they, even if they're genetically the same. The ones which are raised in a cold environment will stick more closely to Bergman's and Alan's rules, so they'll have shorter arms and legs. They'll be over bigger. Ferriness is something that also in animals tends to go with that. So those are the sort of things that happen during lifetime. And then there are genetic adaptations sorry, like adaptations to diet, perhaps adaptations to the way in which fat is recruited to make energy, which have been found in populations which have a long ancestry in cold places. People like the unit. So there are many different layers of adaptations. The cold and I think other animals do that to a certain extent but the fact that humans have more cultural adaptation, potentially more physical plasticity as well. But one of the key ways that we adapt is cultural and behavioral. I think that's sort of the way in which we've managed to inhabit these cold environments, even though that's not our ancestral background.

Andrew MacIntosh: 15:09

That's right. We have this crazy ability to outsource a lot of the kind of things that we would need over millions of years. Through adaptations, we can get them in relatively short amount of time. I mean even just animal furs as one example. I think I saw recently that some of the furs that the Inuit use are actually far better insulating than, like, canadian military grade. You know Arctic wear, so it's quite an incredible thing that people can do. And you mentioned also this idea of replacing, so Homo sapiens replacing Neanderthals, or now we know that there's a lot more mixing. So can you comment then? Is there, are there examples, or what do we know about? Maybe so assuming, and maybe this is a little bit of a lay assumption, but Neanderthals were generally quite well adapted to colder climates climates maybe more so in general than sapiens, physiologically or anatomically, maybe not behaviorally, but so if there is considerable amount of mixture as well, are there some examples of like cold adaptive traits that humans might have generated during the process of interbreeding with Neanderthals?

Laura Buck: 16:16

You mean things that we might have got from Neanderthals. Most of the information we have about sort of adaptive integration is at the genetic level and I don't believe any. I can't think of any traits that are definite the cold adaptive that have come from Neanderthals. There is a huge range of things which have been associated with greater or greater amounts of Neanderthal DNA. Some are to do with disease susceptibility, which seem like they could be adaptive, even if in current people sometimes they're sort of maladaptive. So things like potentially risks for mental health disorders. They might be bad for us now but they could have been beneficial in the past and you could see how, in terms of more infectious diseases, it would be beneficial to take something from a group that's been many generations adapting to the local bacterial fauna and then use it without having to spend that time adapting. But in terms of morphology we're not at the stage where it's easy to say this genetic background causes this gross morphological feature, so it's harder to to make that link.

Laura Buck: 17:25

But there's so many papers about new genetic traits which are linked to Neanderthals that wouldn't be completely confident that no one has said okay, this is related to better use of brown fat to produce energy. Or there might be things that are related to metabolism, but nothing that comes to mind.

Susumu Tomiya: 17:42

Interesting. That reminds me. So I have a kind of a follow up question based on your very interesting paper published in Scientific Reports in 2019, in which you compared morphological variations in the scouts of Japanese macaques versus the prehistoric German people of Japan, and you found that both the macaques and the German people were pretty variable, but only the macaques their skull shapes correlated with the climatic gradient in Japan and not the German people. So, listening to what you've been describing about all these aspects of human evolution, I wonder if humans are somehow less capable of morphologically evolving compared to other primates within the species level.

Laura Buck: 18:42

I don't think it's so much that we're not capable of doing it, because one thing was interesting, that was interesting about the monkeys was that the pattern overall of variation was quite similar to what's seen in humans at a global population. So the ways in which the cold adapted macaques differed from the warm adapted macaques was quite different, was quite similar to the way in which very cold adapted human populations differ from more temperate or warmer adapted populations. I think the level of cold stress that's needed to make that change is just greater. So the reason that we compared the Japanese macaques to the prehistoric German people was that they were inhabiting pretty much the same condition. So we want to say for this amount of cold stress, is the effect similar?

Susumu Tomiya: 19:26

I see, so they both respond to different degrees.

Laura Buck: 19:30

Yes, and I think there are probably other things involved which come back to me in a minute. But I do think culture is one of the reasons why we don't see the similarity between the German and the monkeys in the way in which they adapt, because the German culture was very rich, they had houses, they had fire, they had clothes. You know, they had a very sophisticated way of dealing with the cold, which was not biological, which the monkeys don't have. The other things that might play a part of things like the fact that there's probably greater gene flow between the groups of humans than there were between the groups of monkeys. As you know, the most of the areas where the monkeys live now are quite separate, because Japan's a very developed country in terms of lots of cities and agricultural land. So the areas where the monkeys live, the forested areas, tend to be quite widely separated and so it's not very easy for them to sort of for genes to pass between the two.

Laura Buck: 20:25

Whereas the German there probably was regional. There are regional differences between different groups which can be seen in things like the pottery and the patterns of tooth modification and things. But there's also trade networks that can be shown with valuable artifacts being passed between different groups. So there was definitely sort of large-scale movements between groups of people. So that might have sort of stopped this pattern of regional variation building up as well.

Susumu Tomiya: 20:54

I see. So it might be interesting to compare prehistoric samples of Japanese macaques across Japan, when there was less fragmentation of habitats.

Laura Buck: 21:05

Yes, yeah, if there were such a sample, yeah, that would be interesting.

Andrew MacIntosh: 21:09

Cool In general I think, this idea of and I think, Laura, you've done a fair amount of it but this comparison, using human past, ancient human populations and primate populations to answer kind of big questions. I think for you this interest-specific variation is big. Also adaptations to certain, for example, ecological or climate regimes, I suppose. But can you maybe just comment on, I think, how long have you been studying the Japanese macaque as a model for this or macaques in general for comparison with people?

Laura Buck: 21:42

Since 2015,. I guess.

Andrew MacIntosh: 21:44

Yeah, was that around the first time that you came to Japan?

Laura Buck: 21:47

Yes, 2016.

Andrew MacIntosh: 21:48

Yeah. So maybe, as we kind of transitioned in a little bit, I can ask you and also everyone just heard from Susumu as well, who's sitting here in the studio with us. Excuse me, but I can just ask you what it is that you're doing in Japan here these days.

Laura Buck: 22:05

I'm scanning a collection of a very special collection of macaques that's housed at e-hub, which is hybrid between Japanese macaques and Taiwanese macaques, so I'm scanning the pelvises. When I say scanning, I'm structured light scanning them, so I'm Reconstructing virtual models of their shape, which I will use to then analyze how their shape Relates to the fact that they're hybrids, and also then the two full-breed parents as well, the Japanese macaques and the Taiwanese macaques.

Andrew MacIntosh: 22:36

So one question I wanted to ask that was related to both what you just said now and what you were talking about earlier with adaptations, particularly adaptations of cold, is you're here visiting?

Andrew MacIntosh: 22:48

Well, one of your hosts is Takeshi Nishimura.

Andrew MacIntosh: 22:50

I was a faculty member here at e-hub, has been for many years, and he's also Been putting out some pretty interesting research in recent years and and I think, some that's relevant to this discussion too.

Andrew MacIntosh: 23:00

So I recently discovered a paper of his that was looking at the nasal passages of humans and comparing them also with other primates and Finding that they're not really good at air conditioning, and so I was thinking that I guess nasal temperature should be some way correlated with it, how we can kind of regulate the passage of air at different temperatures into our body Homostatically, which is kind of in theory supposed to be kept at a certain level, and so so I know you've also I don't know if this is related at all, but you've also done some work on sinuses, I think, and I don't know if that has anything to do with, but it's all connected kind of with the craniofacial architecture, and so I kind of wanted to ask you about that as a potentially one kind of adaptation that we didn't make for cold climates, and then, just in general, how you yeah, you think about that that definitely on nasal adaptations to adaptations to temperature, is one of the things.

Laura Buck: 23:54

So Most of human variation in cranial form is drift, most of it is just chance, it's you know who you live near, who you happen to have children with. But there are a few things which, on top of that Imprinted, which have function, and one of those is extreme cold. So as I was saying earlier to sumo, it's, it's not something that has an effect at a sort of medium temperate environment, japan level temperature, but we see adaptation in in populations living at very high latitudes Such that their body shape is different, as I said before, relating to Bergman's and Allen's rule. There and this is on average, you have to remember their cranial shape tends to be Browner, often bigger as well. So that's again relating to Allen's rule, to getting close to a sphere, to avoiding Heat loss, and the no nasal architecture is something that's affected. People who live in cold, dry climates tend to have taller, narrower noses and the internal morphology has changed as well and this seems to be to do with sort of increasing the time passage of the air within when you're breathing in, so it's Warming it more before it goes into your lungs and getting close to your brain and really delicate tissues, so it's increasing the turbulence of the air. So there are differences within humans, and then there's the question of how that differs to other species.

Laura Buck: 25:14

One of the areas where it's been looked at a lot again is with Neanderthals, because there's this, this sort of trope that Neanderthals are cold adapted to the level where Every single feature in any and a towel has been pulled out and said, okay, well, that's, that's a cold adaptation because of blah blah, blah Golden wanting called them, just so. Stories is this Adaptionist paradigm where you look at one thing and you say, okay, well, what would that be useful for? That must be what it's for. So Neanderthals weirdly, in terms of what we know about cold adaptation in nasal apertures in general and this isn't just in terms of humans, it's also been shown in Japanese macaques and also in lab rats they should Neanderthals if they were called up. They should have tall, narrow noses, but actually they have huge noses, they have great, big, wide, beaky noses, which should be really bad for cold adaptation. So this is sort of been this paradox and there are sort of two potential explanations for it. One is that they aren't actually that bad at Recouping heat with their noses. They just do it in a very different ways to humans, and when I say humans I mean home iscipians, which is another argument we can get into, but they have.

Laura Buck: 26:24

So there was a recent study which looked it modeled the airflow computationally through a Neanderthal nose, through a Homo sapiens nose and through cabway, which is, depending on where you stand, homo rudiesiensis, homo hadlopiensis. At any rate it's an older species which probably isn't the ancestor of the two, but it's about 200 to 300,000 years old and found in Africa. And they found that actually the Neanderthal nose was better at conserving heat, better at air conditioning, than the cabway nose, not quite as good as the Homo sapiens, but it just did it in a different way. So the morphology internally was such that there was still longer sort of passage time and it was more efficient than you might expect in terms of recouping heat. So it could be that the nasal aperture or the nose has to stay wide for another reason. That could be to do with something like diet, to do with chewing, it could just be drift gave Neanderthals bigger faces and then they had to adapt to be having efficient nose for breathing in cold climates afterwards. Or it could be that Neanderthals actually needed to dump quite a lot of heat at different time periods. They also have these really barrel shaped chests, which could be a cold adaptation or it could be to do with an active lifestyle. There's some argument that they had very sort of active hunting practices so running after large game, maybe getting quite up close and personal with big game stabbing them, things like that. So if they were getting and they're very muscular, so they're very insulated, so if they were producing a lot of heat, that can be detrimental even in a cold environment. So the large nose might be needed to dump heat at certain times but also try and balance both requirements.

Laura Buck: 28:14

So relating back to sinuses is the fact that all these structures in Neanderthals have been pulled out as being called adapted structures, and that's something that happened with sinuses as well. Since the first Neanderthal skulls were found, people have said that they had very large sinuses and that those must be called adapted, because Neanderthals were called adapted, so it's sort of a circular reason. In fact they don't. So this is some of the work that my PhD was doing, and also Todd Ray, my supervisor, chris Stringer, did some of this previously. But Neanderthal sinuses aren't actually large when you look at their overall cranial size and also there's no evidence for sinuses large sinuses being a cold adaptation. It doesn't work.

Laura Buck: 28:56

When you look at humans overall, the airflow between the sinus and the nasal passage is too slow really for it to be efficient at cooling anyway. So I think that's important in terms of thinking about not trying to pick out every single trait and trying to think of a purpose for it. Traits are integrated, so the sinuses might be related to something else going on in the face, and drift, I think, is a really like neutral processes are something we tend to forget in human evolutionary studies, I think, and they're probably what leads to most of what we see in terms of physical variation between individuals and even at the species level. Tim Weaver and some of his colleagues did a really interesting paper that showed that most of the differences between humans and Neanderthals cranial could be a portion to drift. So I think it's a really important sort of process to think about.

Andrew MacIntosh: 29:43

Yeah, really interesting. I mean, I've noticed that non-adaptationist hypotheses have started to kind of grow a little bit in popularity, but we still maybe it's the scientific training, but we still have this bent on trying to figure out what the function of everything is.

Laura Buck: 29:57

I think it's a problem in fossils because we have such small sample sizes so we rarely get to look at variation, and that's one of the reasons I like using non-human primates, using an extant species, because you can actually start looking at intraspecific variation. How does that compare to between species variation? It's a problem in hybrids as well, because hybrid populations are thought to be more variable, but if you've only got one or two individuals, they might be from different times, different places. It's very difficult to say how much variation there is in a population.

Andrew MacIntosh: 30:25

So Taiwanese macaques and Japanese macaques. So there is a place within Japan where I don't remember the full backstory behind this, but how did Taiwanese macaques end up in?

Laura Buck: 30:35

They were a captive population and they escaped and they'd bread with local Japanese macaques.

Andrew MacIntosh: 30:40

Yeah, and it's been some decades.

Laura Buck: 30:42

I guess that they've been interpreting yeah, yeah since the 70s they were culled, so it hasn't it stopped, I think in the early 2000s so sort of 25, 30 years.

Andrew MacIntosh: 30:53

Yeah, I'm not interested in the hybridization process, but so what are the major, then similarities and differences that you'd be interested in when you look at hybridization between Taiwanese and Japanese macaques?

Laura Buck: 31:03

One of the big differences is size. Japanese macaques are larger and Japanese macaques are a really nice analogy for humans and Neanderthals homo sapiens and Neanderthals because relative to the Taiwanese macaques they're sort of cold adapted, so they're stockier, they have shorter limbs, their faces tend to be broader and flatter, so some of those adaptations that are obeying Bergman's and Allen's rules. So those are the sort of differences that we might expect to see, sort of intermediates, maybe in hybrids. One of the interesting things about this sample is it's a wild sample and the hybrids were growing up in a Japanese environment, so it might have been beneficial to be more like a Japanese macaque than a Taiwanese macaque, although they're from Wakayama, which is relatively far south. So ideally it would be nice to compare them to a sample of the same hybrids that lived in Shimokita or somewhere like right in the far north. But you have to work with what you can get.

Andrew MacIntosh: 31:55

Yeah, and probably not the best idea.

Laura Buck: 31:57

then, transport no no, I'm not going to intervene. I don't. Yeah, definitely not ethical.

Andrew MacIntosh: 32:04

But so you just mentioned that it might be better than for the hybrids themselves to have more, or you indicated to have more Japanese macaque like traits in order to be successful in that environment. But obviously the hybridization process itself, at least in the beginning, is just total random assortment, and so it isn't.

Laura Buck: 32:23

It's not totally random because there's mate choice. So that's another nice thing about a wild population they get to choose who they're mating with. The other hybrid population I've worked with was captive bred so they had less choice. But in this case we see exclusively male Japanese macaques hybridizing with originally with the Taiwanese female macaques, and then more male Japanese macaques going into that hybrid population. And I think there's two reasons for that. One is that males are the sex that moves in macaques and the other probably is that because the Japanese macaques are larger, the males are sort of more prized by the females than they would be if they were the Taiwanese macaques. So to a Japanese macaque female, a Taiwanese macaque male looks a bit wimpy, whereas a Japanese macaque male looks like a really primate to a Taiwanese macaque.

Andrew MacIntosh: 33:17

I assume that the male's dominance interactions would probably come in there too. So if the Japanese macaque males are much larger than the Taiwanese macaque males, they may exclude mating opportunities.

Laura Buck: 33:26

I would imagine. So yeah.

Andrew MacIntosh: 33:28

Okay, so that's interesting. So I'll take back what I said about total random assortment of genes, but the process of being more like a Japanese macaque, if you're thinking of it on an adaptationist's side, that would then require generations. So do you think that, apart from the sexual selection, do you think that there would potentially be any natural selection happening against the more Taiwanese macaque-like hybrid?

Laura Buck: 33:55

I think we have to remember the epigenetic potential. So it could happen on a sort of lifetime basis, not just generationally. So the expression of genes could be prioritized. That may do more Japanese macaque-like, but yes, over the course of several generations. I don't see why that question couldn't be sort of selection. Whether enough generations have passed for that to have occurred is another matter.

Laura Buck: 34:21

My colleague, Ito Sanzuyoshi Ito, has recently published at the moment as a pre-print but it's available at the moment and the final paper will be out soon a paper looking at the entrogenetic trajectories of the Japanese, the Japanese, the Taiwanese and the hybrids, and his results are interesting and they're sort of they're a spoken. My suggestion that there might be this adaptive integration, that it might be beneficial to be more like a Japanese macaque, because he sees the sort of path of development being different in Japanese macaques and Taiwanese macaques, with more or less intermediate between them, as the in the hybrids. But these differences are established before birth. So what I thought might happen would be that plasticity and epigenetic effects might lead to the hybrids being more like the Japanese macaques. But if the these differences are established prenatally, that suggests that that's not the case and you would need something of a sort of longer scale generational change to achieve that which, if you imagine I don't know about Japanese macaques, I'd have to look it up, but in the Rhesus macaque the generation time is about five to six years. You're looking at maybe five generations. I don't know if that would be long enough to see a real difference.

Laura Buck: 35:45

There are studies which have shown relatively quick changes in macaque morphology. There's a famous one where Japanese macaques were taken from a Rashiama and they were sort of honshu middle of Japan, and then half of them were taken to Oregon in Northwest United States and half of them were taken to Texas in the south, and over a relatively short period of time I can't remember how many generations, but two or three generations, I think their body shapes were measurably different. I would imagine that was plasticity rather than generational change, but it's something that would need to be investigated in more detail. I think things can happen more quickly than we expect. The famous studies of Boazes where he looked at the children of immigrants to America. People often emigrate because they don't have particularly good life circumstances where they are, so in their new country their nutrition was better and their children were larger. For example, Some had different cranial shapes which were associated with growth. So things can happen very quickly, but again the mechanism may not be what we're expecting to see in the Japanese macaques Super interesting.

Andrew MacIntosh: 36:52

I also we've talked a little bit about the. I interviewed Devin Shohe. He's a campaigns manager at Born for USA. They managed that Texas population now of Japanese macaques from Arashiyama that was moved there and some of my previous professors in the University of Calgary also had studied that population as well and they had a book published Arashiyama Monkeys East and West or something. But it's quite interesting to think about those animals now encountering completely different environments in a place like Texas, including different set of species that they can interact with like rattlesnakes or so, even behaviorally they must have been in for a rude awakening there, maybe they're more about it than me, but what sort of?

Laura Buck: 37:34

it's been a while since I read the paper. They're captive, but are they free ranging? How much sort of interaction do they get to have?

Andrew MacIntosh: 37:41

Yes, free ranging in confined space? For sure I don't. I've never seen them, I haven't been there, I don't know how big their areas were, but they were basically out out of doors in a kind of naturalistic environment, and I believe that there was a story about them developing new kinds of alarm calls, for the rattlesnakes for example. But yeah, kind of an interesting story.

Laura Buck: 38:02

That's the whole other angle. The behavioral adaptations, right, and how? So this is really relevant when you think about hominins, because we are such behavioral creatures. How ready were Neanderthals and homo sapiens to recognize each other as mates? And that might have been determined by by behavioral patterns. So it'd be really interesting to know if there are any sort of ways in which the macaque mating behaviors differ the Japanese and Taiwanese macaques, whether they it's easy for them to see each other as mates, or if it's only sort of if you don't have any other options or thing. Yeah, I'd love to know more about that.

Laura Buck: 38:35

Yeah, fascinating I think there's a little bit of work on hybrid baboons from Mozambique that touches on sort of male mating behaviors, but I think it's an area that's sort of really ripe for investigation.

Andrew MacIntosh: 38:48

Cool. So I want to ask maybe very specific questions about the kinds of analyses that you're doing here. And you gave a seminar a couple of weeks ago and you talked about mainly about previous work you did at the University of California Davis, the primate center there, or sorry, the California primate National Primate Research Center looking at hybrids of Rhesus macaques so these were Chinese and Indian Rhesus macaques and then the gradient of hybrids between them, and you were specifically looking, in the data you showed, at the pelvic morphology and so, before transitioning to that with the Japanese and Taiwanese macaques, what is the kind of focus then of the analyses that you're doing here?

Laura Buck: 39:29

At the moment I'm scanning the palvases, but that's partly because Ytosana's already scanned the crania. So I'm hoping we can compare what's happening in the Japanese and Taiwanese macaque hybrids to what's happening in the Rhesus macaque hybrids in both the cranium and the pelvis. That's partly because I'm interested in applying this to the fossil record. Most sort of fossil studies are done on the cranium, partly because of preservation reasons, partly because it's sort of most informative about taxonomy and how where things fit. So it makes sense to look at the cranium. But the pelvis is also interesting because it's one of the areas where we see most difference between humans and the andatals and also because it's sort of crucial to survival. If you can't successfully pass a fetus through its mother's pelvis then both of them will die. So it's a really sharp selective pressure and how that works in a hybrid affects whether you can have a viable sort of hybrid, whether there'll be more than one generation effectively of hybrids. So both of those are interesting, but also they might be constrained in different ways. So I think it's important to know whether there's certain parts of the skeleton which are more or less affected by hybridization. So that's the first step is comparing what happens in the hybrids in the two different species and in the two different areas.

Laura Buck: 40:46

The reason that I want to sort of get a better handle on sort of the the different variables that affect the outcome of hybrid morphology, is because, ultimately, I want to be able to build a model that we can apply to the fossil record that will probably be with crania, because there aren't enough palvases in the fossil record to be able to build anything of interest.

Laura Buck: 41:07

So I want to know things like if the parents are more or less related to one another in terms of sort of evolutionary history, in terms of split time, how does that affect what happens to the hybrid offspring? If they're morphologically or phenotypically more or less similar, how does that affect what happens to the hybrid offspring? And the sort of part of the body we're talking about is also interesting in that context. So if we're looking at what happens in the cranium, it might be good to be able to say but yeah, but there's a lot less variation in, there's a lot less effect in the cranium than there is in other parts of the body, for example. Then if further down the line we want to say something about femora or something, we might know that there would be probably more or less effect than there would be in the cranium.

Andrew MacIntosh: 41:51

Yeah, it's really interesting. I mean, I think, when people think about hybridization, the idea of the chimera comes into mind. Right, you can have these completely, you know, lion body, eagle, head kind of, which is obviously, in naturalistic terms, an impossibility based on contingency and how things have to work and what you just said. I mean it just, you can't just completely reconstruct a skeleton like a mashup of different species.

Susumu Tomiya: 42:15

I think it's important to remember that until fairly recently, hybridization was thought to be a pretty rare thing, at least rarely successful phenomenon, among, I'd say, mammals at least, and so it's relatively recent. Development in population genetics and ancient DNA techniques and so on have given us a much different picture of the importance of hybridization as an evolution of the human force, even among mammals, and so for that reason I think what Laura's studying is really interesting, even beyond the realm of human evolution.

Laura Buck: 43:01

I think one of the things I'd like to do is to put humans back a bit more into the context of other primates. I think often anthropologists. As anthropologists, we don't think about humans as being part of the natural world enough. Obviously, humans are distinct in many ways, but some of the lessons that we can learn from other species are very applicable to hominins, and presumably the other way as well. So I think it's important to remember the sort of zoological context, if you like.

Susumu Tomiya: 43:34

Sure, there are major differences between, let's say, macargot hybrids versus baboon hybrids in terms of skeletal morphology and how the hybridization produces morphological traits.

Laura Buck: 43:56

Some of the sort of foundational work looking at non-human primates, particularly looking at non-human primates in the context of human evolution, was done with baboons. Becky Yakerman was sort of the person who popularized this, although James Chevrode also was important at the beginning looking at tamarins. So some of the very classic studies are done in baboons and they sort of lay a foundation for sort of what we have come to expect in non-human primates and what Becky and her colleagues found in, particularly this one sample of baboons which was a captive population that's housed in Texas, and these individuals show what she characterized as a hybrid signature, so that they have sort of a lot of variation in the hybrid population. They have extremes of size and they have sort of weird traits, so what are called non-metric traits, things like the sutures in their skull might go in weird ways or they might have extra teeth or rotated teeth, things that probably weren't functional. You can imagine that having the extra teeth might be problematic, but it doesn't seem like it affected their lives too much. They weren't seeming to die of these conditions or anything. But definitely the hybrids were distinctive, because what we have seen more recently in other populations is that this sort of level of strangeness in hybrids is less apparent.

Laura Buck: 45:20

There have been several studies on wild populations of platterines, of new world monkeys, things like howler monkeys and I'll see the other one Colortricids, tamarins and marmosets, and it's difficult to compare them in several ways because they're working with live monkeys, so they're not looking at their skeletons, so they're measuring size in a different way and, unlike the captive populations where there's a pedigree, so you know exactly who's given birth to whom, which gives you the amount of hybridity in each individual.

Laura Buck: 45:56

These are often estimated hybridity, so they are known to be hybrids from their coat colour, for example.

Laura Buck: 46:06

But it seems like there's more variation in the hybrid population but there are fewer extremes and in my own work I found even less of this pattern.

Laura Buck: 46:18

So in my research macaques from California, which are also a captive population, so they know from pedigree, the hybridity there was very little effect. It was a very subtle effect and some of the things which previous researchers have suggested affect the amount of sort of hybrid signature of things, like how closely related the parents are in terms of sort of genetic distance, split time between those two taxa, and also how physically different or phonetically different they are and the baboons which form those classic studies have been separated for a much longer evolutionary history than the macaques which I'm studying and some of the platterines are sort of intermediate. It's not a simple relationship and a lot of the work determining the effect of these things have been done on plants or fish so it's not always clear the effect that it would have on non-human primates. But it certainly seems, and it's sort of intuitive, that the less related the parents are, sort of weirder the offspring are.

Laura Buck: 47:19

Interesting yeah.

Susumu Tomiya: 47:20

Well, if I remember right, in the case of baboons hybridisation is known to have occurred not just among congenital species but across different genera. So the depth of that phenomenon is probably much deeper than in the case of macaques.

Laura Buck: 47:41

Yeah, I think there are other examples in primates of cross-generic hybridisation as well, but I don't think they've been studied to the point where we can easily say you know, if it's cross-generic, you expect to see this effect. If it's congenital, and also it's not like there's a quantitative definition of a genus or of a species.

Susumu Tomiya: 48:02

Yeah, unless there are some kind of general species.

Laura Buck: 48:09

I feel like some species are more splittery and some areas of non-human primates are more split and some are more lumped, and it might depend on you know how many different researchers have been there, all of the history of their study, as much as it does the actual diversity within that group.

Andrew MacIntosh: 48:30

I want to follow up on a couple of as soon as questions there. One of them was. So now we have kind of a greater appreciation for the the degree of hybridization actually happens in nature. But I think when you gave your seminar you gave some statistics like in vascular plants you knew about 25% of the species have hybrids, and birds, mammals and butterflies was only about 10%. And I wonder so with vascular plants, I mean, we're not talking about cultivars here, but you're talking about naturally hybridized species and do you think those differences so two and a half times more plants than vertebrates and butterflies having hybrids Do you think that's a natural process or do you think that's a? We're missing something. Is it an artifact of sampling? Probably both.

Laura Buck: 49:15

Plants. I'm not very familiar with plant genetics, but as I understand it they can do all sorts of weird things, like have multiple copies of chroma.

Laura Buck: 49:23

They can have tetraploidy or quadruploidy or whatever. That would be where you can have four copies of a gene, of a chromosome, but not in every. They seem to be much more flexible in sort of what works being a plant. So it, with my incompleteness, my incomplete understanding, it would make sense if they hybridize more readily, just also because of the mechanisms of passing on their genes, maybe they have less choice about who they're interbreeding with. If you're a wind-pollinated plant, you don't get to choose who you're fertilizing. But I think there's. That's.

Laura Buck: 49:55

The paper which I cited is already relatively old and I should update it. I think it's 2007. So there's probably many more. There are many more instances of hybridization known in invertebrates, in mammals, for example, but we're discovering more all the time. And also it goes back partly to what we find as a hybrid, what we define as a species. We're splitting and renaming primate species all the time. So the Tamarins which James Chevrod studied, for example, are a new genus now to when he wrote the paper. So I think those are still intergeneric hybrid examples. But you could imagine a situation where something goes from being intra-generic hybridization to between generic hybridization just because we've decided to rename it.

Laura Buck: 50:47

And so we might decide something as a hybrid one minute and decide it's not a hybrid another minute.

Andrew MacIntosh: 50:52

So some of it is definition yeah, super fascinating, I mean the whole like the species concepts that we have. We have so many different ways of defining species and so I guess maybe where you come down kind of determines too how you think about that situation. But the other side of it is like I think maybe this is one of the issues that comes up with the Japanese macaque case and various other ones. If you think of conservation actions, these days there are some cases where creating hybrids might actually be positive for preservation of certain genotypes, although it's very controversial.

Andrew MacIntosh: 51:27

One example is that I think there was a case in Florida with the Florida wildcats, so mountain lions, I suppose they have their pumas and really bad situation with the local population. That was just really not viable. So you can bring in wildcats from other states, for example, to kind of hybridize with that population and it seems to be kind of successful. So the hybrids are a little bit more successful in their reproduction and survival and so it's a form of genetic rescue. And I think you mentioned and something that fascinates me is this Groller Bear example as well, where if you encourage the hybridization between grizzly or brown bears and polar bears, you may be able to kind of I don't know if it's changed behaviorally, but the requirements for, like the strong arctic environments that they can maybe better adapt to changing temperatures and climates and find new foraging habits. So maybe this kind of challenges our general idea of species purity and I wonder if maybe you can comment on that a little bit as well.

Laura Buck: 52:39

Yeah, I think it's a complex and difficult area because there's sort of bad options both ways or potential positives in both ways. I think there's a difference between sort of human mediated hybridization in the case of the wildcats and to my knowledge the Groller Bears are sort of doing it by themselves. They're not being led to do that. I think you have to be so careful to like human intervention in species. I am not saying it could never be helpful, but we just have such a bad track record of messing with the balance between species because the web of interactions between species is so much greater than we appreciate. On the other hand, if we have led something to the brink of extinction, then I can understand that wanting to try and do something about that. And is there really that much difference between bringing a new species in which adds to the gene pool and replacing a species that's gone extinct, like, for example, at the moment there's been a beaver reintroduction in the UK?

Andrew MacIntosh: 53:40

Yes.

Laura Buck: 53:41

So far seems to be going well. So I just think it would have to be done so carefully to avoid, you know, leading to more problems than you solve. And then you end up sometimes with sort of ego projects like the potential reintroduction what do they call it? De-extinction of mammoths, where some poor elephant might be implanted with some sort of hybrid offspring, which just seems incredibly unethical. So I can see the temptation, but human meddling seems dangerous, yeah, when animals are doing it themselves. I think that's more difficult, or no, probably more straightforward in a way, in that you know, if that's the only way that species can survive, then perhaps that should be allowed. We shouldn't try and control that. On the other hand, you are potentially losing biodiversity, which is a problem overall. We don't want sort of to homogenize populations.

Andrew MacIntosh: 54:41

Right, this genetic swamping.

Laura Buck: 54:43

Yeah, because ultimately variation is important and if we have, you know, one population out competing another and then something changes, then that's going to be problematic or the niches which they fill will not be the same. So I mean it'd be good if we could not lead to the situations where these hybridizations are necessary, so the, you know, the habitat destruction and the anthropogenic hunting and all that sort of thing could be brought down, and that would be great. But that's probably not likely. So I think I'm glad that I don't have to wrestle with those issues. Personally, yes.

Andrew MacIntosh: 55:20

So one of the things I wanted to, while I have you here in the studio, talk about is the kind of methods, the methodology and especially advances in kind of doing the kind of work that you're doing. So I think in your presentation and maybe the reason you're here is doing a lot of 3D scanning of bones in the collection you talked about geometric morphometrics and I wonder if you could just comment on the kinds of methods that you're using to analyze the specimens that you have and what's kind of changed, say in the last you know handful of years or something, to what the kind of state of the art is now and where do you think it's going.

Laura Buck: 55:58

Geometric morphometrics is relatively new. It's a way of analyzing shape quantitatively, but it keeps the geometric part of the name is to do with keeping the geometry. So if you take a bunch of independent measurements you lose the overall shape of the object, whereas if you look at, compare something using landmarks which is what we do in geometric morphometrics, which means basically putting points on the same place, like for example between the eyebrows in every individual, and comparing where that is in 3D shape, so you can look at how those landmarks in an individual relate to one another and look at their overall shape, how that overall shape differs between individuals and how that's related to variables of interest such as environmental variables or admixture, hybridization, that sort of thing. So it's a really powerful suite of techniques and its origins are quite old more than 100 years old but they used to be done with mathematical calculations on paper or early computers and it's only really with the birth of more sophisticated imaging that is taken off in the way that it has. Probably in the last 20, 30 years it's become much more prevalent and the types of imaging techniques which have really made it possible are CT scanning and then surface scanning methods. So at the moment I'm using a structured light scanner which sort of bounces off light in a stripey pattern and the way in which it's reflected back to a sensor is interpreted into the shape of the object. So it's pretty clever.

Laura Buck: 57:33

I think I talked about this before, but the scanner which I brought with me, which I plan to use, was even. It's very clever because it's something that's supposed to be very portable. It's a handheld thing that looks a bit like an iron and you basically slowly move it over the object in question and then you can reconstruct single scans into an object. Unfortunately, the scanner which I brought all the way to Japan and which I have used previously with success turned out to be really bad at capturing monkey pelvises, probably because they're very thin, they have sharp edges and they're quite small, so they sort of scatter the light and we're not enabling it to capture good pictures. So I was lucky to be able to borrow another scanner from Professor Hirasagi here which enabled me to carry on scanning in the way that I'd planned to, but with a different model, and this sort of shows the proliferation of different scanning machines in the last few years.

Laura Buck: 58:32

So when I first started scanning things with a laser scanner, which is related to a structured light scanner. There was a thing called a next engine which was super popular, relatively cheap. It had a rotating platform and a sort of eye that you pointed out which sends out the laser, but the quality was not great. Since then, every time I've talked to someone about what they're scanning or go to a different institution, it seems like they have a different piece of kit. There's so many different pieces of technology now and they all use it slightly different ways of doing things.

Laura Buck: 59:01

The scanner I'm using at the moment is the same sort of model as the next engine in that it has a rotating plate, which is great because it means that I don't have to be scanning all the time, so I can do something at the same time. And I think it helps because it's sort of got an internal coordinate system, because the platform is fixed rather than moving the iron-shaped thing over it. So I think it helps it to know where it is, which helps it to reconstruct the scans better. There's a lot of sort of cheaper versions than there used to be as well now, and even to the point where you can get pretty good service scans with an iPhone. This was one of my backup plans. When my scanners stopped working, if I couldn't borrow another one, I thought, well, maybe I can just buy a new iPhone but worst case scenario come all the way to Japan and I'm not sure.

Laura Buck: 59:50

If one thing I was worried about in that context was I'm not sure the resolution is good enough for a small enough object. But certainly people have used them very successfully for things like archaeological digs to show what they look like, and I believe the resolution is actually pretty good. Photogrammetry is another big sort of growth area, so that's taking loads and loads of pictures and stitching them all together. So these are all relatively cheap, relatively accessible. It's all relative. They're not cheap Ways of collecting the data which can now be used for geometric morphometrics.

Laura Buck: 1:00:24

I think the gold standard is still CT scanning because, for me at least, because the waves go through the object, you get the entire structure. You get the internal structure and the external structure and you don't miss anything, whereas with the scans that I'm taking at the moment structured light scans if I'm doing something like a skull around the back of the eyes, where the bone is quite thin and sharp, it can be very difficult to get every little sort of invagination of the skull, whereas with an X-ray particle it just passes right through the internal information is also really great, but a CT scanner is usually not portable.

Laura Buck: 1:01:03

It's much more expensive. Potentially it damages the DNA of whatever you're scanning, which may or may not be a problem, it seems like. As long as you use the correct parameters, it's probably still worth scanning things, especially before you then sample them for DNA, because then that information is lost, but it's something to be considered. So there is like a whole range of methods now, which most of those were available in some shape or form a few years ago, but that they've just become much more accessible to your average researcher.

Susumu Tomiya: 1:01:36

Yeah, I just want to add that. But when I was in graduate school, mainstream geometric morphometric analysis was still two-dimensional, based on pictures. But there's only so much shape you can capture of, let's say, a squirrel skull if you're only taking pictures in two-dimension. So this is another area where there has been a rapid development in technology and affordability of 3D scanners has been greatly helpful and has made science much more powerful.

Laura Buck: 1:02:14

Yeah, definitely. I remember doing things with mandibles as well as two-dimensional, and you have to be so careful to keep the orientation correct and to account for size and things like that. And one of the first pieces of kit I used I started off. I was lucky to have CT scans, although the quality if not all of them was great because they were medical CT scans.

Laura Buck: 1:02:32

But the microscribe was a big thing at that time, which is a thing that looks a bit like an angle-poise light, but it has a point on the end and every time you touch the place of interest, the landmark, you push a foot pedal and it records its coordinates in 3D space. And they were relatively cheap and relatively portable, so they were used a lot. But they have calibration issues. They can get confused about where their orientation is and, because you don't have the scan, if you forget a landmark or you've put it in the wrong place, you can never go back and recapture that data, so it's a lot less flexible. I had a similar sort of problem with the technology with the microscribe. When I went to the American Museum of Natural History as the early part of my PhD, I took a microscribe with me to collect data on the skulls that were there. Happily collected data for a week got.

Laura Buck: 1:03:23

I don't know, several tens of skulls. Got home, I re-scan, I used the microscribe on some that I also had CT scans for. They were completely incomparable. It must have got uncalibrated, probably on the journey. There was a way of homing it, which I did when I got there, but probably there's internal consistency in that sample. I could probably use it just on its own, but I couldn't use it as part of my PhD, so that was a week's worth of data collection that was unusable. So this is the problem with technology. If I was using a tape measure it wouldn't be a problem, but it also obviously allows you to do things that you couldn't do with a tape measure.

Andrew MacIntosh: 1:04:02

So I another interesting thing about geometric morphometrics is that we had another graduate student recently finished who was using it for on macaque faces as an indicator of pain face and so a way to kind of try and better understand the welfare status of individuals. But it seems like it's used in a lot of different, a lot of different kind of areas of science and it also seems to be really amenable to or fits really well with modern advances in AI. So I wonder if you have any. So how is? I don't know if you've already experienced any people in colleagues using AI technology now to do analyses of structures, or where do you think that's gonna have the biggest impact in the science that you do?

Laura Buck: 1:04:48

I think it could be really great because there's so much prep time in that sort of data collection and data sort of cleaning. Though the only place where I've used it which I'm not sure if it's strictly speaking AI, but programs like Checkpoint you can build a template, so you do a landmark set on one skull and then it will automatically apply it to all the others in your sample and then you go through and you change it. So there's still that. I think the important thing is that there's still that user involvement. You check they're in the right place. But it saves you a lot of time and also it takes out some of the human error when you're landmarking. I don't know to some of the landmarks with semi landmarks as well, I might have 200 landmarks, 300 landmarks on a skull. It's so boring, it's really hard to stay concentrated, so it's really easy to put them out of order or to miss one, and then it's very time consuming to go back and work out what your problem is, because you find that it's not working, so you must have done something, so then you have to take a really long time to go back. So I don't think that that's an important part of scholarship to spend that time doing it. I think a computer can do that sort of thing much better and then the human can put the energy into trying to work out what the patterns are, to doing the analyses sort of downstream.

Laura Buck: 1:06:08

When I was doing my PhD I did a lot of measuring sinus volumes from CT scans.

Laura Buck: 1:06:13

So this is virtual segmentation going through CT scans and saying, okay, that area is the area I'm interested in, and basically coloring it in virtually with a felt tip pen to select the region I was interested in and then joining all those regions together to make a structure and then measuring it. And the reason why it's particularly hard for sinuses is their air. So you can't do it by threshold. You can't say I want everything below this density threshold to be a sinus, because it would take all the air in the skull and all the air around the skull as well. So it had to be done more or less manually and it took so long and I don't think even after doing I don't know 200 individuals I was that proficient at it that a machine probably couldn't have done it better. And now there are sort of semi-automatic and automated ways of doing that which weren't available now. And I think that's fantastic, because that is not the best use of the student's time To be honest.

Andrew MacIntosh: 1:07:08

I mean, I know a lot of you know in my lab. We do a lot of peristology work in the laboratory. So you're under a microscope counting little eggs that you see perisa eggs and samples of macaque feces or whatever it's gonna be and totally agree. So we have some imaging techniques that should be able to handle that for us, but a lot of the technology is still currently sub-human level probably.

Andrew MacIntosh: 1:07:30

That's going to change Absolutely. There should be more data sets out there, training data sets, and it's gonna get a lot better with accuracy. So we're just kind of in that transitionary period, but it's certainly a lot of tedium that people go through.

Laura Buck: 1:07:43

It's interesting to hear about those stages in other fields. I feel like in my field it takes such a long time to get the data and that's sort of that. It takes longer than other people, so it's nice to know that other people also have to spend, you know, months, getting to the point where they can even start getting the numbers to analyze.

Andrew MacIntosh: 1:08:01

Yeah, exactly Susumu. How about you? Any thoughts on the horizon for AI?

Susumu Tomiya: 1:08:06

Yeah, so I agree with what Laura was saying. At the same time, I think the geometric morphometrics is a more established method and the results are probably more easily interpreted than what AI speaks out. So with the GM, you define the points of interest which may be anatomically important or evolutionarily important, Whereas if you just feed AI with a whole bunch of scanned images, well, it may be able to distinguish among very subtle differences, but you don't always know what exactly the machine is recognizing. So I think that's one of the issues that Vanessa, one of our graduate students, had with the application of neural network to the Makak pain phase recognition. She ended up relying more on the geometric morphometric analysis in the end. So there's definitely a potential for AI application. But yeah, like you said, I think we definitely need the transitional period and GM is still quite valuable?

Andrew MacIntosh: 1:09:19

Yeah, it's interesting to think. I mean, what does a computer see when it looks at these things? Versus what do we see? And are they comparable in any way? Certainly doesn't seem to be at the moment, but it reminds me also, laura, in your talk when you were talking about the hybrid pelvic morphology and the Rhesus monkeys from California. In the end, your results, you have some differences, but it's very minor and a lot of overlap, maybe no huge patterns coming out of it.

Andrew MacIntosh: 1:09:48

I don't wanna get into the specifics, but maybe related to what Sasumi just said about the AI, it also seems like it might make it a little bit hard to know what the importance of those changes might be. So, like, how can we kind of separate and this is gonna kind of transition into my last question, which is more about you've mentioned a few times over this interview already but how should we consider variation and how can we extract meaning in that variation? And then maybe you can walk that one into the last question, which is more about where are you kind of going with this science? And you mentioned a few times that you're really interested in applying what you can learn from more or less?

Andrew MacIntosh: 1:10:32

modern assemblages to kind of human or hominid fossil record, and so how can we kind of tease out, like the meaning from the variation in that respect and where do you wanna take it?

Laura Buck: 1:10:45

Okay.

Laura Buck: 1:10:48

To leave you with a very simple final question yes, it depends what you mean by the importance. I think that the effect of hybridization on the variation in that sample in particular is not important. I don't think it's changing the lives of those monkeys in any way, so it's not a functional difference, if you like. I do think it's interesting to understand how variation is patterned overall, to understand what parts of it are due to different causes, so that we can unpick the sort of neutral from the functional and understand what causes the neutral variation, because that still leads to variation, which is what evolution is acting on. What I still think the variation in those monkeys is important in a different way though, because it helps us to understand what happens when hybridization occurs, which helps us to know what to expect in other species, particularly in the fossil record. So would we be expect to be able to see it in fossils that we find, or would we expect it to be too subtle to be able to define? Morphologically? Is the pattern similar, even if the magnitude is different? So the monkeys that I was looking at the two Rhesus macaques Chinese and Indian Rhesus macaques are physically pretty similar to one another. So it's not that surprising that the hybrids don't have a huge effect. So there's not a huge effect of hybridization on their offspring. But if the pattern is the same in individuals which interbreed, which have more difference between them, then we could still use that to build the relationship between hybrids and hominin tags. I think I'm just trying to understand better the variables which shape hybrid expression in offspring basically. So what effect do the parts of the body have? What effect does the distance between the parents have? Particularly, what effect does phenotypic morphological difference between the parents have?

Laura Buck: 1:12:53

One of the reasons I'm so interested in that is that humans and Neatals, homosapiens and Neanderthals, are very closely related but they're really different skeletally and I'm interested in why that might be the case and the effect that it has on their hybrids.

Laura Buck: 1:13:08

This sort of maybe it's a bit of a pet subject, but I think one of the reasons that they might be so different is that they do have this layer of cultural adaptation to a greater extent than other animals. Neanderthals are also very complex in terms of cultural behavior. So if you are able to adapt more culturally and behaviorally, maybe you are free to vary more neutrally in terms of your skeleton. There are other reasons why they might vary more as well. Perhaps their environments are more different than the macaques are, but I feel like the release of constraint on the skeleton, which might be due to cultural buffering, might play a really interesting role and might tell us about the ways in which humans, or hominins as a whole, are different from other primates. So, even though I'm interested in putting humans back into the primate context, I'm also interested in what makes us distinctive.

Andrew MacIntosh: 1:13:58

That sounds like such an important task, given the changes that we're probably about to go through in the planet and whether we're actually culturally able to adapt effectively enough to handle those.

Laura Buck: 1:14:11

I think the trouble is it's not just capacity, it's what's the word.

Andrew MacIntosh: 1:14:15

Willingness.

Laura Buck: 1:14:19

Yeah, it's not just the ability, it's the working together, it's the seeing beyond the immediate it's working for the common good rather than the individual good. History tells us that humans aren't very good at those things.

Andrew MacIntosh: 1:14:31

Yeah, I wish it were different. Well, laura, is there anything else that you wanted to add to or that I've missed, or you wanna finish up with?

Laura Buck: 1:14:40

I thought we might talk about what's it called niche construction a bit, but I guess we sort of talked about that a little bit. But I just think that's a concept that doesn't get enough. I mean, it's not a little known concept but one that perhaps doesn't get enough airtime in terms of human evolution, because it does go back to this idea of the relationship between culture and environment and behavior and this link. So I've been talking about how we use our behavior to adapt to the environment a lot, but of course our behavior also changes the environment, which then has an effect on us. So it's this real ratchet effect, it's this we shape ourselves and then we shape our environment and our environment shapes us.

Laura Buck: 1:15:24

Probably the most canonical example of this for humans is agriculture. So perhaps the start of agriculture was due to environmental effects, perhaps Maybe a drying and a cooling leading to people collecting more food sources as a sort of protection method. But then the way in which we changed the environment due to agriculture had effect on things like disease prevalence, sedentism, things which are also behavioral, like division of labor, specialization, leading to differences in technology, and then ultimately to the way in which most of us live today and the massive sort of climate and environmental disasters that have come about down the line and some of the ways in which our bodies have changed since the start of agriculture are reflected in that. Things like less bone density, greater heights, early puberty, all these sorts of things. So I think it's really interesting to think about the way in which we sort of construct our own evolution.

Andrew MacIntosh: 1:16:23

Absolutely. I know that that's something that's quite interesting for, and maybe part of the story behind the kind of renaissance of group selection thinking, this kind of social needs construction as an example of it, where we kind of create the social environments and then maybe some versus other social environments are actually more successful. So kind of an interesting story, but humans are definitely a perfect example of a species that creates. Are there any other, though, examples that you can think of apart from us?

Laura Buck: 1:16:59

Their own needs, change our environment.

Andrew MacIntosh: 1:17:01

I mean, there are some classic ecosystem engineers, right, you think the beaver brought up earlier is like a great example of a species that has a huge influence on its environment, and then probably there's been some feedback mechanisms in there. Yeah, absolutely.

Laura Buck: 1:17:13

I think so. I think there's bacteria that definitely create the environment in which they exist which has probably shaped them, sort of changing the pH and the temperature.

Laura Buck: 1:17:23

Termites, for example, build these huge cities. They probably couldn't exist outside them anymore. I think lots of things do in a sort of smaller way. We're unusual in the way that we sort of do it in lots of different ways. So Robertson his co-author, whose name I can't remember off the top of my head, have this term that we're specialist generalists. So you get your specialist like a panda who can only do one thing. You get your generalist like a raccoon who eats anything. Humans different. Humans are specialists in different things, and so that's one of the things that has allowed us to sort of inhabit all these different niches. So we sort of we're beavers, but also bacteria, but also termites. You know, we do everything in different ways and that's sort of how we've managed to colonize everything.

Andrew MacIntosh: 1:18:04

Yes, and as we continue to look beyond what we've already colonized in the hopes of colonizing the unknown at the moment, I hope our ability to kind of create those niches in which we can continue to evolve doesn't slow down anytime soon. But I think that's a good place to close. So, lorbuck, thanks so much for joining us on the primate cast. Thank you, sussumu Tomia. Thanks again for joining us in the studio.