Almost Cannibals

This is not the Dahmer cast exactly. This is mostly going to deal with animals, and towards the end of the episode, we are going to discuss some some of the questions surrounding cannibalism among ancient humans. But again, if it don't worry, We're not going to be talking about like like true crime cannibalism here. That's your thing. There's plenty of that out there, you know where to find it, that's right. So we we've frequently discussed predation on the show,

and we've of course discussed cannibalism as well. You know, we've talked about how it factors into any given organism, organisms, life, whether it's predator or prey, as well as its role in human evolution. And I think we've also tried. I mean, obviously it can be fun to talk about, especially grizzly predatory practices in the wild, especially among like invertebrates, But I feel like we tried to do our best to

dispel predator hatred, right. We We did a whole episode a while back about why predators are so beneficial for ecology and even for for human civilization. Absolutely, and you can't look at predators just as the villain of any given peace, no matter how dramatic the music and a

given nature documentary might be. That's something I found watching just so many nature documentaries with my son, is that earlier on he would get a little wigged out by scenes of predation or pending predation because they just have such overly dramatic music and they're really playing into the idea that the predator is the villain. Yeah, but I'm I'm happy to say that he is. He's really gotten out of that. It's very rare now that at age he just turned seven. Uh, it's very rare that he'll

be wigged out by predation scene. In fact, there will be scenes where say, like some young lions or ripping apart of water buffalo or something, and I'll be a little wigged out. I'm like, this is getting kind of bloody, and I'm like, you sure you wanna finish watching this scene. He's like, oh, yeah, it's cool that they're hungry. No, no, he's not. He's not bloodthirsty for it. But he he has he's already has his appreciation that. Yeah, those those

animals are hungry. They need to eat. This is how they eat. This is part of the natural order of things. Yeah, that's really cool. I mean it's it's a hard thing to appreciate because of course, within a human context, if you see like one human chasing after another human trying to hurt him, we know that's morally bad. That's something to to oppose. When you see a predator chasing prey, Yeah, the prey is fighting for its life, but the predators

also fighting for its life. It's just obeying its instinct. That's part of what it does. And if if the predator doesn't get some prey, it too will die. Yeah, a wrong move on the on the part of a predator giving chase could lead to its death as well. Via via starvation, if it were to say, in draw leg. But of course, one of the strangest forms of predation and one that often seems to even when you see

it among animals, even when you know better. One that I think still strikes many people as a kind of taboo or a kind of violation is when predation is turned inward on one's own kind, when it turns into cannibalism. Yeah, and we've and we've again we've discussed cannibalism on the show before, especially sexual cannibalism, I think more recently, Yeah, we did a whole episode on sexual cannibalism, especially as it appears like among arachnids, in which there are some

fascinating behaviors. It's far more complex and interesting than just like well, male spider mates with a female spider and then the female eats the male. They're all kinds of economic energy dynamics going on different behavioral adaptations to that, to that kind of world. It's a really truly complex

and interesting subject. Yeah, And I think economics is the way I always try and and and focus on it, you know, just thinking of just the the economy of uh, turning sunlight into flesh, which is basically what happens with the food chain. And so you're going to reach a point where even another member of your own species is energy. And what are you to do if you are, say a scorpion or something. I mean, especially with the with the scorpion, which is you know, UM tends to be

a solitary organism. Uh, you know you're not going to let that energy just go to waste because you have some sort of you know, heightened scorpion morality or you know, our ethical system in play. No, you're gonna you're gonna show down on some cannibal meat. Well, no, again, animals are not humans. We with human brains can appreciate reasons that one should not eat one's own kind. Yeah, but if in the rest of the animal animal world cannibalism

is widespread. So I today's episode, you know a lot of what we're gonna deal with this this idea of almost cannibals, which is something I started thinking about while I was vacationing in Belize. I was out there with the family, snorkeling, and I was slipping through a guide book for Caribbean organisms um aquatic organisms, and I came across a couple of entries for the head shield slug. Okay, this is kind of like a it looks sort of like a hammerhead slug. Yeah, it looks like a hammer

head sea slug. They're also known as bubble snails um and and these are members of the clade um Cephalospidia, and the these names head shield slugs bubble snails. The name refers to their common head shield, as is a broad head that's used for burrowing in the sand and it helps to keep the sand out of their mantle cavities. And most have have shells, but some species have have to have a reduced shell and some have what's known

as a like a bubble shell. Now I never got to actually see one while snorkeling, but the two entries in the book, I got my my mind working because there was leech head shield slug, which was this beautiful dark blue indigo creature with bright yellow stripes. This is one of the counterintuitive things about nature, is that clearly one of the most beautiful types of animal in the entire world or sea slugs. Yeah, yeah, absolutely, uh. But then there was another one. There was the mysterious head

shield slug. That's what it's called that was in in this in this book, and this may have been an older book. There may be updated names for some of these now, but this one looked had the color of just rotting vegetation swearing camo. And as for their diets, the book listed that the mysterious head shield slug feeds on other sea slugs, especially the the lettuce sea slug. Okay, fair enough, right, there are a lot of sea slugs

out there, and there's a lot of competition in aquatic environments. Um, you know, we're dealing with a very large subclass of the gastropod of family here. But the leech head shield slug its diet was listed as other head shields, So it's getting even closer to home, right, Yeah, so it's not cannibalism. You know, they're not the same species. Uh, they're in the same family, but I suppose, you know, it's it's the name that that gives me pause. The

fact that they're both classified as headshield slugs. Well, that is a kind of interesting question to say, Like, Okay, we know cannibalism happens pretty often in the wild, and we'll discuss the conditions and just a minute here, there are some limitations that are imposed by genetics, by the energy economy, and by epidemiology on on how far you can go with practicing cannibalism as a lifestyle as an animal.

Uh So they these limitations are in place. Some of those limitations might not be in place if you're preying on something that's a lot like you, but is not exactly you. Right, So, yeah, that's something we're going to talk about here. You know, what are some examples of um near cannibalism, Like what are some of the more closely related prey predator relationships out there in the animal world?

And then what does that say about us? What does that say about the way that humans think about cannibalism? In a weird way, this episode topic even got me thinking about some of the strange economic dynamics of digital media. I promise that's not as boring as it sounds. We'll come back to that later. I don't know, digital media cannibalism. That sounds pretty exciting and probably just like spot on and just a fact of life. So let's refresh a

little bit about cannibalism. So, to eat one's own species is to commit an act of cannibalism. Now, sometimes especially we'll get into a few cases later on. Sometimes this word we the word cannibalism is used for things that are not quite cannibalism. But that's where we get into that gray area of near cannibalism. Yeah, and it's sometimes said with the derogatory context, but I mean again, it's something that like, obviously, if you kill and eat your

next door neighbor, that's a bad thing. But animals this is just sometimes an adaptation that animals have, that's right. And there are many different varieties and classifications we've discussed. Somebody's done the show before. Sexual anibalism for instance, which like you said, can be can be, you know, rather complex. It's not just a situation of well I made it with him, I guess now I'll consume his flesh. A lot of times it depends on, for example, what the

male brings to the table in the sexual encounter. There are some species of spider where if a male shows up with a food gift for the female, for example, he can he can be more likely to avoid being cannibalized after mating, whereas if he shows up and just wants to mate and doesn't bring her anything to snack on. He's more likely to be cannibalized. And this sort of makes sense, right, like or is he is he contributing additional food resources to the development of the offspring? Right?

And then there are other examples like matrophagi where babies uh, where the offspring consume the mother um. You know, they're they're examples where um of a mother organism will consume the young. And a lot of these cases of cannibalism in the while, they're they're going to be influenced by uh, you know, economic um uh resource uh deprivation issues like are those offspring going to survive? Is something threatening them?

Should then the energy of those uh of the offering be uh brought back into the host or into the

mother organism. Yeah, Now, I detect among the literature in in zoology and behavioral ecology and all that that there there's been a shift in consciousness about cannibalism over the previous decades where I think it used to be more common for scientists to believe that cannibalism would was something animals would only do under extreme scenarios, like if they were in a starvation scenario, you know, just like the absolute limits of survival, and that has increasingly it's increasingly

become clear that that's not the case. Though animals don't, you know, they're not usually going to practice cannibalism as some kind of primary mode of living. There are actually a pretty wide range of scenarios in which cannibalism occurs, and we're we're documenting more and more of those scenarios all the time. It's not always just star ovation at the very edge of survival and the peaks of stress. Yeah. So it's one of these things that is, you know,

we're learning as ubiquitous in the natural world. It it offers some really key advantages, though there are some downsides. It remains highly popular without ever becoming like the thing right like you made your species might engage in cannibalism for a number of different reasons, but you were not going to become an obligate cannibal like that is where the system would collapse. Yeah, and I think there are some reasons that that's sort of impossible. I'll talk about

that in just a minute. It reminds me a lot of some things I've heard about the band Primus. I've heard stuff, but okay, well I'm going with you. I'm not saying that the members of Primus are cannibals, but rather um, I think it was less Claypool himself, who at one point pointed out that like they were in a good place popularity wise, like they like they never completely went out of fashion, but at the same time,

like they never just really blew up. Like I feel like most people, Uh, if you asked them, they might say, oh, yeah, Primus is cool. I did Primus. I myself have enjoyed a prime Primus in concert before, but I would I would never say Primus is necessarily my favorite band. Uh. Likewise, cannibalism, It's okay, I'm with you. I see what you're saying. Yeah, I mean, yeah, they're Primus has long been By the way, my candidate for what I joke about is like the

least sexy or least romantic possible music. So if you're trying to like figure out what to put on for a Valentine's Day dinner or something like that, so you could go with like your Marvin Gay or you know, your classic romantic options, and at the other end of the spectrum you've got Primus. Yeah. For me, Primus is more like driving around music, you know it nothing will scribe if you if you were thirsting for primus, nothing

else will do. But then there are plenty of other cases where it probably is not going to be the ideal soundtrack for life. But anyway back back to canalism, So yes, there it can be especially useful in certain ecological situations. Uh and and there are a lot of key benefits to the individual. On the other hand, it can impact community dynamics. But the exact shape and scope

of a species cannibalism it varies greatly. Yeah, exactly. Um So, so there are these obvious, like you're talking about, economic and evolutionary limits on what forms cannibalism can take, even though it can to each individual animal that practices that give all kinds of benefits. One example would be that you know, when one species regularly eats another species, it is common that the prey species is in some way more vulnerable, it's smaller or weaker, definitely more numerous than

the predator species. You can't make a diet out of eating mostly or entirely animals that are say as good at killing you in self defense as you are at killing them in predation or the economics of acquisition. Just don't work out, right, You're not gonna go chasing down something that's got all the same muscles and teeth and claws and all that as you. Right, you have to have some sort of an advantage, either a direct biological advantage or some sort of behavioral advantage such as pack

hunting or something like that. But but even in those cases it can be exceedingly risky. And and think again, how I mean, I think we sometimes because we have medical care, we uh downplay the risks to an animal in the wild of a mirror like you know, leg injury or something like that, which can be fatal to an animal in the wild, while you know, you can

just go to the hospital and get fixed up. So if adults of a species focus on other similarly sized adults of the same species, hunting probably becomes too dangerous to sustain as a regular practice. Also, a species cannot make a diet out of eating mostly or entirely animals that are less numerous than itself, because it's going to run out of food and starve, or it's gonna have to switch to a different food source. If an animal were to eat primarily or entirely members of its own species, Uh,

there would immediately be a couple of problems. And number one, you would have to think, if it's a sexually reproducing species, this behavior is probably going to interfere with mating and lead to depletion of mates. Probably more importantly, the species couldn't survive. It would sort of eat itself to extinction. Like if every member of the species needed to eat one other member of the species every month in order to not starve to death. Your best case scenario is

having the number of individuals every month. Now, maybe you think you could replace those through rapid reproduction, but where does the energy to create and grow those new bodies come from unless you're eating even more of your own kind. So it seems kind of I was trying to find an example of something that comes close, but it seems to me you can't really have something like an obligate cannibal species, something that only eats its own kind. That

seems like an an absurdity. So you have that fact, but then you also have the fact that we do observe lots of in species cannibalistic behavior in the wild in the wild, and we know that this can only take place in sort of limb did conditions and scenarios, and we're discovering more and more of those types of scenarios all the time. Here's a common one we know.

You can't just eat members of your own species for your entire diet and have every member of your species do this for your entire life, for the species would cease to exist. But within certain phases of life, cannibalism can be a primary strategy. Consider the larval stage of many amphibians. Uh you have like cannibal morph larvae of tiger salamanders. We talked about those in our episode on salamanders with Mark Mandica. Or think about the cannibalistic tadpoles

of toad species like the spadefoot toad. And this is where the biggest tadpoles in a small body of water will eat the smaller ones to survive and grow even bigger. It's sort of like a letting letting the strongest of the of the litter absorb the energy of all the others. Now, obviously this kind of strategy can't be continued for the amphibians entire life cycle, but it can work in a phase of the life cycle because the other energy inputs

into that phase. Another great example from another episode we had with a with a guest was thinking about intra uterine cannibalism in some sharks species, like we talked about with Mara Hart, where some unborn sharks will swim over and eat their siblings or half siblings before they even leave their mother's uterus. Do we talk about cannibalism with all of our guests? I don't know. It does seem to come up a good fit, but maybe we do. I don't think we brought either of these up, did we.

I mean, I guess they were just an innate part of the cut, the conversation and the expertise of the guests. Maybe we just invite creepy guests. They're not creepy. Maybe we're creepy. We're talking about cannibalism right now. We're definitely creepy. So while cannibalism can't be the entire diet of a species, it can be an important supplemental part of a diet, especially in scenarios of environmental stress, and it can even

reduce competition when times are tough. One example here is that cannibalism, according to what I've read, it's much more common if you live life in the water. Oh, yes, definitely. Yeah, if you're wet, you're probably involved in cannibalism in some way. It just happens a lot more in aquatic environments. For example, when fish are foraging for food, one type of energy source they will often come across is little sphere ules of lipids and energetic materials floating in the water. Other

fish eggs. Uh. These fill the waters of the ocean by the bazillions, and this will include some eggs of their own species, which they basically just eat discriminately along with the other eggs. We recently did the episode on the Christmas Island crabs. Oh, yeah, where they just stuff the crabble are right into their mouths. Yeah, I mean, how do you know if it's your own offspring. Chances are it's not. There's so many out there, it's probably

somebody else's. Also, I think I accidentally said that they will eat them discriminately. Obviously they eat them indiscriminately, is what I mean. Fish don't discriminate. But yeah, it works out because fish produce a lot of eggs. Under the evolutionary assumption that most of the eggs, many of the eggs at least, will not survive and the eggs of one's own species are only a supplemental part of the adult fishes diet, not the whole thing for the whole species,

which again would be a problem. But the phenomenon of adults eating young of their own species actually happens in many scenarios outside the water too. Obviously, it would make no sense for animals to have instincts to kill and eat all of their own young, but there is some selective strategic snacking of this kind. Like often rodent mothers will eat some of their own litters, especially those that

are sickly or don't seem like they're gonna thrive. Male carnivores like lions, will sometimes eat the cubs sired by another male, and this tends to increase the female lions receptivity to mating and the pride. Yeah, this is seen in bears as well, for sure. Oh yeah, definitely. And then there are some really strange cases that were observing again more and more all the time, even with animals

once thought to be herbivores engaging in occasional cannibalism. Here's when I came across hip pose what hundred percent herbivores right, Well, that this one one I always assumed. I mean you hear to hear about like the vast amount of vegetation that a given hippo needs to consume, and that is their primary diet. They mostly are herbivores, but occasionally they'll just be versatile. So we used to think there are

a hundred percent herbivores. They're mostly herbivores, except now it's been observed that sometimes they'll kill and eat an impula, or even sometimes they will eat a fellow hippopotamus. Well, they are ferocious. I mean, we can't take that away from them. So there are just more and more examples all the time that science is documenting about ways that animals will occasionally or opportunistically or even in some controlled ways,

regularly engage in direct in species cannibalism. Yeah. I was reading the amazingly titled two thousand tin paper Cannibals in Space, the Coevolution of Cannibalism and Dispersal in spatially structured Populations and U. And in this the authors point out that the propensity for cannibalism, you know, it's going to vary

considerably among even closely related species. And then a lot of questions remain concerning exactly what drives variation and the evolution of cannibalism across and even within a species, and the can and the same can be said for the evolutionary consequences of cannibalism. Yeah, a lot about cannibalism remains an open question. There's still a ton we don't know.

But I think one thing that is emerging is what we're getting some good ideas of what the major downsides to cannibalism are, like, what are the limitations that are imposed on it as a practice, And so I want to mention I think three major ones that there may be other ones, but these are three major ones. One is, if you're practicing cannibalism, you could end up eating animals closely related to you. And given the self preserving tendencies of genes and evolution, there's going to be a selection

pressure against this. Genes will tend to come about and become prevalent within the species that say don't eat each other if you have this gene. Also, as we mentioned are here, it's a risky to try to kill and need an animal that has ald the same equipment you do, the teeth, the muscles, the fighting abilities, it's easier to go after weaker prey, and there's usually some kind of weaker prey out there. But there are ways around both

of these. I mean, for one thing, you can try to avoid eating animals you're closely related to, even if you're eating your own species, by evolving ways of detecting relatedness. So maybe you know there's some gene that allows you to recognize who is your from your immediate family and not eat them. I actually have an example of this.

We'll come back to that later. Okay. Another thing you can get around is that animals with cannibalistic tendencies can get around the problem of fighting uh something, fighting something just as big and dangerous as as you are by

eating smaller, weaker con specifics. And this can take the form of sexual cannibalism, like in some spiders like the red back spider, where there's a huge difference in size between the males and females and it works out just fine for the females to eat the males after mating, or this can happen with adults preying on larvae or smaller juveniles of their own species. But finally, one last big problem with cannibalism, and we'll come back to this. When you eat your own kind, you put yourself at

risk of catching diseases and parasites. You're more likely to consume or otherwise expose yourself to something bad that can infect your species. If you're eating animals that are already of your own same species, Yeah, you're basically diving into a swimming pool of this other individual's potential viruses and illnesses. You're you're diving into a swimming pool marked bio hazard. Yeah.

So there's always a cost benefit calculation going on. And I'm not saying obviously that the animals are doing this calculation consciously in their heads, but somehow this calculation is being worked out. There benefits to cannibalism, there's an obvious energy advantage, and there are all these downsides, And so the circumstances and and the specific traits of each individual species are going to interact to determine when cannibal is

m is actually appropriate. Alright, Well, on that note, we're going to take a quick break, but when we come back, we're gonna continue exploring this topic. And we're going to kick off by discussing this idea of near cannibalism a little bit more than thank you. All right, we're back. So we were just talking about the limitations, Uh, well, all of the examples we see of cannibalism in the natural world, true cannibalism where members of one animal species

are eating members of the same animal species. Uh. And then limitations on wind cannibalism can be practiced, and what what might hold it hold it at bay from becoming too prevalent. But there are probably examples of animals doing something that is not quite cannibalism, but where they're eating

something that's kind of close to them. Yeah, And so I started looking around for answers on this, and one thing that that did come up when I was looking for near cannibalism and um and you know, scholars, scholarly works and academic papers, I ended up running across it

in some myth papers on myth and medieval histories. And I found this rather telling, not so much about like what's going on in the animal kingdom, but about like why I'm fascinated with it, Why this idea of near cannibalism is perhaps even a little more interesting than interesting

to me compared to apps absolute cannibalism. So For instance, there are medieval accounts of the Danes roasting animal flesh to eat alongside, like right next to heaped the heaped human dead from a battle, so like feasting on the battle grounds with their slain enemies around them, almost sort

of suggesting a mental connection. Uh yeah, And of course, again these are accounts of the Danes probably you know, with it with the idea of portraying them as being in the state of of near cannibalism, Like look at that, they're just cooking their meat right next to the bodies of the dead. They're just there's just one misstep away from going full cannibals. Romans would never do anything like that.

Another thing that come up came up with was the myth of like Cayan, which we recently discussed, and there's an act of near cannibalism cannibalism there as well, where the flesh of a human is offered up to the god Zeus to say, like, hey, Zeus, do you want to eat some human flesh? Like they're trying to trick Zeus. Uh. Now, granted Zeus humans a god, but sort of yeah, I mean it seems like species enough, like if if if

the gods of Greek mythology can mate with humans. It seems like that they should be like biologically close enough that eating us would be a cannibalism, right right. And of course you know the gods, especially the Greek gods, they were down for any number of horrible acts. They would turn into an animal to mate with a human, that sort of thing. But I guess the thing is that they probably are not going to look kindly on being tricked into doing anything vile that they didn't want

to do. No, And of course when Zeus was almost tricked into eating human flesh, he retaliated. By their different tellings of the story, sometimes he retaliates by just like killing a bunch of people. Sometimes he retaliates by turning the king who tried to trick him into a were wolf, has pointed out by seed down him in the Good, the Bad, and the Ugly portrayals of Vikings in the Fragmentary Animals of Ireland, near cannibalism and near paganism were

considered the apotheosis of the evil. Yeah, you see this in many ancient sources. It's like cannibalism is sort of held out as it's it's the archetype of barbarism. You know, it's like the ultimate act that in itself in an iconic way shows that somebody is not civilized and not good. And there's something as he's pointing out her, there's something tantalizing about like that that that moment before cannibalism, that or that moment before paganism, like that slip that decline

into this barbarous nature. Uh, the idea that, oh, they're not cannibals now, but I bet they'll be cannibals tomorrow because look what they're doing right now. And of course, uh, in the animal king um, all these species we're you know, we're looking at cannibalism is already in the blueprint, like it's already part of the of the of the act.

But there is there's something about about about that to the the human mind, I think, you know, because we can't help to think of of of all of these changes taking place not against the the in in the time scale of evolutionary history, but we think about it within the terms of lifespan and the choices that we make.

But anyway back back to just like purely the the animal world here I did can run across a study that points at a possible case of cannibal fueled speciation, because I think that's something to interest to think of, because it's like if I'm if if one if within a species, members of that species are deciding to just go full cannibal like they're like, oh, I can just eat my own species all the time. If that were to happen, could that conceivably lead to a speciation event

where the cannibals become their own species. Oh yeah, that's an interesting question. And so this this study I found in two thousand seventeen study, and I should stress that this is an unrefereed preprint in bio archive, so caveats on not going through peer review, right. But in it, the author's point to cannibalism in South American um annual killie fish that's austro lebias as a possible speciation event.

So they're they're they're presenting what they refer to as an alternate hypothesis for giant dwarf speciation where where some of these uh we're basically the chilly fish here have evolved in sympathy without geographic separation by character displacement and cannibalism but in this day, the authors are discussing cannibalism in South American annual killie fish, and the idea here is that it could it could be a speciation event going on here, that that accounts for giant dwarf speciation,

So basically bigger, bigger killy fish versus a smaller chilly fish, and cannibalism could play a role in that right right there, That that could be what's what's pushing this species into two species based on the size of the individuals. Yeah, that's interesting if I am understanding their argument correctly. Okay, Now, there's one thing that I had been thinking about as a potential case of near cannibalism, which we've already sort of discussed in a previous episode called Strange Milk. So

I won't linger on it too long. This has come up before, but I just wanted to remind us of one form of feeding that could be seen as analogous to cannibalism, but without the element of lethal predation, and that is found in various systems where an adult animal feeds its offspring with some part of its own body. Ah. Yes, so this is not predation. The offspring does not necessarily kill and eat the adult, but it could be considered a form of alternative cannibalism, as if I could like

off one of my arms and feed it to my kids. Interesting, and the great example here is the type of amphibian known as Sicilians. Now it's not spelled like from Sicily. It's c A E C I L I A N. Sicilians are amphibians. They're kind of like frogs and salamanders, but they've got no legs. They look like a cross between a snake and a worm, like a like a wet earth snake. They tend to live underground, so we rarely see them, and if you do see one, you

might mistake it for some kind of gigantic worm. Yes, I remember we we talked about about the about the Sicilians with Mark Pendina. Oh yeah. And one of the things we talked about with the Sicilians and the strange Mailk episode was that after the mother of a Sicilian species called a boo Langarula titan us gives birth, she turns her outer skin into a nutrient rich secretion for

her offspring, and then the young gross special teeth. I've seen these referred to as shaped a slotted spoon so that they grow special teeth, uh quote, which they used to peel and eat the outer layer of their mother's modified skin. And that's a quote from a two thousand six paper in Nature. So basically, the mother turns her skin into like this cheese like substance, and then the juvenile worm like creatures chew off their mother's skin. They

peel her like a like a vegetable. This is interesting. This is it's very it's consensual. It's it's not just a situation where the young eat the mother, but the mother is mother said is essentially saying, here, take of this specially prepared skin and eat it in remembrance of me. Yes, take of my body and take of my skin. I mean. It seems to combine multiple elements of the Texas Chainsaw

Massacre together at once, but somehow without the massacre. So there's the peeling of skin, peeling the skin off, and a form of near cannibalism, but without the elements of predation. The the the willing adults says, try my skin. It's good, and they do. That's what we aid for the the to to reboot the Texas Chainsaw Massacre franchise is we need to we need to take the mascre at mascre at just have everything else happening consentually, and ultimately that's

going to be more terrifying. I think it's just about a consensual human barbecue cook from from Texas. Yeah, you know, I've had that thought with a few different horror films that have come out where you know, they're there, you know, people behind them are sometimes pushing the boundaries and they're like, and it's all about like horrible things being done to people. And I'm and I'm thinking, you know, the creators here obviously they think that this is that this is horrible,

and this is a terrifying vision of of life. But but what if what if it what if everyone was engaging in it willingly, like you know, then it would put an entirely different spin, and arguably a more thought provoking and even terrifying spin. I feel like that's often what black mirror is. Black mirror is often like a what would otherwise be like a horror movie or a horror show, except most of the time the people who are the victims of whatever is happening in the episode

get involved consensually. Yeah, because it's technology because the technology exactly. Like, for instance, if you had a Friday the Thirteenth film where all of the young people went off to camp and the thing that they all really hoped for, that the thing they desired most of all, was to be massacred by the mass killer that runs the woods. You know that that would fulfill some sort of deep desire in them, some desire for I don't know, like teenage

martyrdom or something like that. Ultimately, like that that that gets me thinking a lot more. There's a sort of almost element of that in Hell Raiser. I guess people are looking for trouble messing around with a puzzle box. They should know better than Yeah, And of course that would make sense. Clive Barker, especially in the younger Clive Barker, I think he did engage in a lot of a lot more subversive treatment of these things. Well, speaking of

Clive Barker, okay, on that. You know, I thought of Clive Barker already earlier in this episode when there were a couple of times where you just said flesh and I was like, you kind of can't do that without saying it in the Doug Bradley voice. Yeah, obviously, we're big fans of some of the hell Raizor films, and and uh, and I definitely hold up some of Barker's work, especially his books of blood short stories. There's some some really good short stories in those collections. Yeah, I've always

meant to read them, might never have yet. But we should get back to near cannibalism. Well, let's bring things around to the human realm, or at least the you know, the the ancient human realm. So let's talk about humans and Neanderthals. So evidence has been presented and sometimes dismissed regarding regarding cannibalism among both ancient humans. Though it gets kind of complicated because we're talking about ancient humans, but

technically you call these modern humans. They're they're ancient from our standpoint, but they are evolutionarily modern humans. So uh, at anyway that there's there's their arguments and evidence for both these ancient modern humans and the indertal is engaging in cannibalism. And as we've discussed on the show before, the evidence that scientists look for when they're talking about that,

they're looking for signs of processing on the bones. In other words, it's not enough that a human or a neandertal skull was caved in by heavy object, But are there signs of the bodies having been systematically or ritually stripped of meat or marrow for the purposes of consumption? And uh so, so that's one of the things they

look for. And as Bill Shoot points out in his his excellent book Cannibalism, archaeologists generally want to match this sort of evidence up with similar damage on the bones of game animals from the same site, so that way they can say, look, this is what these people were doing to the bones of animals that were clearly praise a prey species, and here's what was done to the

bones of other members of the species. And then you have more of a direct comparison to make here, so that you can say, this looks like this was cannibalism. That all makes sense. There's some pretty convincing there's some pretty convincing evidence that Neanderthals engaged in cannibalism, at least survival cannibalism. And Shoot points out in his book that the near Neanderthal species Homo antecessor quote, may have simply considered others of their kind to be food, and he

pointed out. You know that again, this is hardly out of step with the rest of the animal kingdom. Cannibalism is ubiquitous, so it's not surprising that Neanderthals or Neanderthal ancestor, or that Homo sapiens engaged in this practice. But what what's interesting us the most for this episode is the

question of near cannibalism. Right, whether ancient modern humans considered Neanderthal's prey or vice versa, how much uh consumption of this, of this this other man like creature was going on, this, how much near cannibalism was happening. So for starters, we have some competing theories, but for the most part, we

don't know exactly what happened to the Neanderthal. They obviously they went extinct, and we know that they likely transition from Homo antecessor to Homo Neanderthal plenis about about a hundred and fifty thousand years ago, and then they went extinct thirty thousand years ago, So that's kind of the the period of their existence as far as we understand it.

One hypothesis is that that's out there is that humans in the Neanderthals interbred and that they simply became us, or at least they became those of us with some portion of Neanderthal DNA and uh, and there is there is DNA evidence to support this, and then there but there's some that to take issue with leaning too heavily

on this idea. Apparently, paleo anthropologist Ian Tattersall, who Shoot interviews in the Cannibalism book Um this guy, is a critic of the idea, and he argues that quote structurally, anatomically, and presumably behaviorally too, Neanderthals and modern humans were very, very different, and he says that while a certain amount of genetic exchange definitely took place, he doesn't think that

they were absorbed into our population through inter breeding alone. Now, interestingly, Tattersall points out that modern humans and Neandertals managed to share the Near East for a long time, but this was before we became creatures of symbolism, as Shoot puts it, quote, an advanced symbolism driven species. These new humans at least outcompeted the Neanderthals for resources, and it's reasonable to expect

that they did a bit more than that. Right when you look at at certainly the way humans have have treated other groups of humans, um, you know throughout history. Now, some researchers have argued in support of of of predation and cannibalism that that Homo sapiens uh hunted and consumed Neanderthal meat. But there's currently no clear fossil evidence that this occurred. So it might seem uh like something that

they would have done. We can, we can point to aspects of human nature and and uh in humanity's historical treatment of others, but when it comes down to the hard fossil evidence of it, when it comes down to looking at bones and looking for signs of processing, uh,

it's just not there. Again, we have clear evidence of cannibalism in either group of Homo sapiens eating Homo sapiens and neandertals eating the ander dolls, but uh, if it occurred, we don't have any evidence of actual intragenous cannibalism between

the inder dolls and Homo sapiens. That's interesting. That being said, I think if if you were to present me with the time machine and make me place money on the on on the the chances that humans in Neanderdals, I would personally um want to place my back on humans eating neander DoLS. Well, i'd say it's probably because humans will eat anything. That's true. If something existed, humans probably aided.

I bet generally a safe bet. Now, let's back up out of the human realm here, and I want to come back to something you said earlier about how a particular cannibalizing species might make sure that it's not cannibalizing its own young Oh yeah, or or members of its own near family. Because then you the closer relative within your own species is the more genes you probably share with them, which makes it more likely that some of those genes would would discourage you from eating other carriers.

And so I found a recent article that deals with this. Max Plank Society article titled a Peptide against Cannibalism from April of twenty nineteen. The researchers noted that nematodes in the genus pristianchas we're all all about some cannibalism because their favorite food is worm lark. So how do you keep from consuming your own offspring? Well, the answer, they said is that they carry a quote small highly variable

protein on their surfaces. So what they do is they experimented by offering adult worms of different uh of different species again within this genus. Uh, they gave them their own larva to potentially eat larva of a closely related species or larva of a related line within their own species. And in all cases they avoided their own larva but tore into everything else, so they were they were totally fine for eating another species. It's closely related to them

that near cannibalism. They were also readily engaging in an absolute cannibalism. But uh, this peptide was at least aiding in their identification of their own offspring and preventing them from eating uh those uh those larva. They identified this particular gene, which they called self one, as playing a key role in distinguishing self from non self. However, it doesn't seem like it's the only factor in the decision

to attack or not. And this is ultimately one of those areas where more research is going to be needed. But it does give us some idea of the kinds of of mechanisms that are in place, that kind of fail safes that are in place to keep cannibalism from just decimating a species. Yeah, and it's really interesting trying to work out exactly when and how those could controls fall into place. All Right, we need to take a quick break, but we'll be right back. Alright, we're back now.

I want to talk about something related to what you were just saying, especially when it comes to praying on the larva of your own species or related species. Uh, this is a case of true cannibalism, but with interesting features. I want to talk about the cane toad or Ranilla marina. So the cane toad has an almost beaut to fully

horribly ironic history in Australia. I'm sure, I'm sure all of our Australian listeners are pulling their hair out right now because if you if you read Australian writers talk about the cane toad, they there's I don't want to over generalize, but there is very often utter revulsion just the idea that they want to beat all these things to death with a sock full of quarters. Now, we we don't encourage wanton violence against wild animals, but there's

a reason behind this. So in the nineteen thirties, Australia had a problem protecting sugar cane crops from populations of a pest known as the cane beetle, and in order to control beetle populations in sugarcane agriculture, they introduced a South American toad. I think this was a nive. It was the cane toad. They brought it to Australia because it was believed that this toad would eat up the beetles that were getting to their crops. And this turned

out to be a horrible idea. Uh. The cane toad became a kind of breakout character, right, It's like the fawns circle, you know. It's like it took on a life of its own for the continent of Australia. It did eat some cane beetles, but it also became extremely numerous and ate all kinds of other insects, and its

populations in Australia just exploded. So it's another case of an already unbalanced environmental situation due to agricultural activities and then they intentionally introduce an invasive species and things go

out of whack. Very bad idea. And what's worse, the native marsupial and reptile predators of Australia, like crocodiles and like coals that might have been expected to control and exploding toad population by eating the toads were totally unprepared because the cane toad produces toxins that kill the predators that eat them, So since the cane toad was out of its native range, the predators had no resistance to these toxins and no one stinctual avoidance of the cane toads.

So simply introducing these like poison candy toads into the ecosystem was devastating to some predator populations. But this threat to predators doesn't apply only to the marsupials and the reptiles like crocodiles that might eat the adult cane toads. It would also apply to perhaps smaller predators that tried to eat the cane toads also poisonous eggs. The eggs have similar poisons. So I was reading a New York Times article from two thousand eleven about research on cane toads.

The articles by Natalie Angier, but the the article tells the story of a scientist named Dr Richard Shine, a biologist at the University of Sydney in Australia, who began to notice years back that cane toad eggs were being depleted by something, and at first he assumed that some predator was at risk of mass poisoning by eating these killer toad eggs uh to quote from the article. Follow up, field Stead soon revealed the identity of the caviar thieves

to the researchers astonishment. Dr Shine said it was cane toads themselves, or rather their tadpoles, which would swim over to each fresh batch of vanilla eggs and quote desperately consume every slick black sphere that they could find. And then a two thousand eleven study in the journal Animal Behavior found that not only do cane toads cannibalize eggs

from their own species, they strongly prefer them. When given the option to eat cane toad eggs or other food sources like similar eggs from another amphibian species, the cane toads went right for the delicious cane toad eggs. And this was just the cane toads that did this, It wasn't other uh frogs amphibian species. Now, remember that while lots of species practice cannibalism under some circumstances, no species is exclusively obligately cannibalistic like that would make no sense.

But what if you're kind of edging in that direction by at least in one stage of life, preferring to eat your own kind over other forms of prey. Yeah, we're definitely in that near well, we're definitely in that that zone where it's cannibalism. But is it potentially becoming something else? Now? You would think since this is tadpoles eating eggs of the same species, you think maybe once you metamorphos into an adult cane toad, you'd get past this,

uh this problem? Right? The answer is no. Studies have also shown that that like midsize adult cane toads like to eat smaller, younger cane toads. They even have like deceptive lure tactics where they will wiggle the toes of their back feet in water to attract smaller conspecifics and then just literally swallow them whole. So I've, as we've discussed, there's lots of occasional opportunistic cannibalism in the animal world. But what causes the cane toads to go so hard

after their own species? Why do cane toads prey on other cane toads so aggressively, and the researchers here in this paper i mentioned hypothesize several answers with regard to the campbalization of eggs by by cane tode tadpoles. Number One, it eliminates rivals who you're probably not related to, and this has to do with the specifics of the timing

of ovipositing and mating by cane toads. Obviously, it doesn't make evolutionary sense to eat your own brothers and sisters, but due to the timing of cane toade reproduction, if you're a cane toad tadpole and there are eggs in the pond with you, you can be pretty sure they belong to some other family of cane toad's. Number two, eating the eggs speeds up the maturation of tadpoles. Obviously

it's free energy. And three, the resource is abundant since it's poisonous and other potential predators can't eat it, but you can, since cane toads are immune to their own poison, so they're kind of like the de facto specialized predator of their own young. It's it's like when you know somebody orders something for lunch, and there's one thing out on the buffet that you're the only person in the office that likes. So it's all for you. Enjoy this

braised red cabbage robbers. And there's a quote from from Dr Shine in that Times article where he says, quote, we're talking about a tropical animal that was relocated to one of the driest places on Earth. Cannibalism is one of those clever tricks that makes it such a superb colonizer and a survival machine. Talking about the cane toad um. Now, of course this does come with some of the regular downsides of cannibalism, like it came across the two thousand

eleven paper with a pretty great title. Also, Richard Chin was one of the authors on this quote. You are what you eat parasite transferring cannibalistic cane tod So you know, do cane toad's risk infection and paras parasitization by eating their own The answer is, oh yes. When a cane toad eats another cane toad and infected with, for example,

nematode lung worms. This study found that the cannibal toad can end up with viable lung worms in its own body, so they are paying this cost for their cannibalism behaviors. And nevertheless, I was reading in another context that cane toads are so aggressively cannibalistic that that cane toad juice from the poison glands of an adult cane toad is one of the best imaginable baits for a trap for catching cane tone tadpoles. Okay, I think it's a cane

tone cane toad tadpoles. That's a tongue twister. Uh So it smells like eggs, right, because they have these same chemicals and poisons, And it's an ingenious method for removing the tadpoles of this invasive species from a water source without harming other creatures. Like the cannibalistic tadpoles are attracted to it in swarms because of course they want to eat the eggs of their own kind, and other animals

are not really attracted to it at all. So you can put traps out with this and catch thousands of cane toad tadpoles and almost nothing else. But I think it seems like this species in Australia in particular favors cannibalisms. Aggressively because it's a tough physical environment, like they need to reproduce in water, and yet it's a relatively dry landscape. And yet at the same time, there's an abundance of

their own species due to a lack of adapted predators. Interesting, So I feel like one of the crazy things about this is that a lot of what they're observing here it's it's it's nothing you would observe, at least on this scale in their natural habitat, Like they're the cane todes of Australia have this kind of bloated and and an natural space in the ecosystem that has yet to be uh, you know, sort of recalibrated by other factors. Yeah.

Now I don't know what they're what they're cannibalistic tendencies are like within their native range, it might be something equivalent, but but this seemed to be focused on the ones that are in Australia, So I'm not sure how prevalent this would be in the species as they live in South America. It's like, if you know, if cannibals took over a date care, like and you observed it on like the first day of activities, you know, it's like

everything is going to be crazy that first day. Hopefully by day three or four things would have have settled down and or the police had shown up, etcetera. Uh. And of course before that, before the cannibals took over the daycare, you would not have this um, this out of balance scenario in which to observe how things would

take place. That's a beautiful analogy. Wrout. Before we wrap up, I wanted to mention just one more type of predation that we might consider a kind of close analogy to cannibalism, and that is when you kill and eat an animal that is not the same species as you, So it's not cannibalism, but which makes a living the same way

you do, maybe does the same job as you. And this brings us to a biological concept and as intra guild predation, in the words of entomologists j Rosenheim and Jason Harmon into intra guild predation occurs quote when two consumers that share a resource and which therefore are potential competitors, also engage in predator prey interactions with each other. So you've got two different species competing for the same resource.

Like how at different times. Maybe Elmer Fudd and Yosemite Sam are both trying to go hunting for bugs Bunny. But what if instead Elmer Fudd kills and eats Yosemite Sam. See, this solves two survival problems at the same time. It provides an immediate meal. You get to eat Yosemite Sam, and there's energy in that. But it also reduces future competition for the webbit. Right, all right, it's a it's a basic Freddy versus Jason scenario. Right, Yeah, that's pretty good.

So the benefits of this kind of thing are obvious, and there are a couple of versions here. There is asymmetrical inter guild predation, and this occurs when two species compete for the same prey resources and one of those two species also kills and eats the other. And then there's what you might guess, the other half of that, the other side of that coin, symmetrical intriguild predation. It's when two species are in competition and they also both

kill and eat one another. If one predator is regularly bigger than the other or something. This kind of two way mutual predation can often cross the lines of life phases, where say one predator adults of one predator prey on the juveniles of the other predator. Okay, So with asymmetrical um intriguild predation, there's always going to be probably a clear winner, yeah, Like the the larger of the two competing species is going to be the one that eats

the smaller. But in symmetrical interguild predation, it could go either way depending on body size, phase of life, or other factors of superiority exactly. And so this type of stuff often happens in insects and arthropods that share the same prey, like in some centipedes, but it also occurs in large mammalian carnivores like canids and fields. They often prey on one another when they're competing for the same food resources, for example lions and wolves, or coyotes and

foxes or bobcats. According to a n paper in the American Naturalists by by Palomari's and Caro uh quote, interspecific killing among mammalian carnivores is common in nature and accounts for up to sixty eight percent of known mortalities in some species. So there's some carnivorous predatory mammals for which more than two thirds of their deaths are caused by other predatory mammals. And because inter guild predation accomplishes two different goals at the same time, inter guild predation can

be extremely useful as the survival adaptation. It's a very efficient way to do things. Of course, since members of the same species are often in competition for the same resources, the same advantages that apply to inter guild predation often apply to straight up cannibalism. Right because you know you, you and the other one of your species you're you're

probably also in competition. But straight up cannibalism is more likely to come with the other downs sides, such as reducing the gene pool of your own species, making making more difficult, exposing you to more parasites and diseases, and so forth. Now you said you were going to bring all this back to social media. No that I was.

I was thinking about this and I started to think that I see parallels between the strategy of intra guild predation and some types of business strategies, especially like in digital media where we work. So why don't you think about this example? What did Facebook due to the rest of the web? Like digital media companies are in competition for audience. You can almost think about audience as their prey in a way. They make money when more people

spend more time on their side or their platform. Facebook was a digital media company in competition for users attention and time, and their competitors were the other places where people might spend their time on digital devices, other websites, other apps, other platforms. So it seems to me Facebook said, you know, instead of just competing with these other media platforms, I will eat them. And that's sort of what it did.

Right So now instead of just going to your blog or homepage or whatever, people would go to your Facebook page or just follow you on Facebook or rely on Facebook to keep people updated on what you're doing, whether you're a person or a business or a content provider. And I think the analogy holds that Facebook functions like

an asymmetrical intriguild predator. Here it gets double benefits both by getting a direct meal off of you, like it gets the traffic that you would be getting elsewhere that gets just subsumed into its diet of traffic, and it reduces competition in the future by training people evermore to just go directly to Facebook instead of to other sites.

And apps, And it makes me wonder if there are other examples in the business world where there is something like intriguild predation going on, where where one business gets double benefits out of assuming or subsuming another one. Yeah, I think you may have something. You may have a point there. I mean, also, it's very easy to imagine any of these large media companies as kind of a bloated cannibal king feasting and blood soaked on a on a pyramid of bones of its competitors. Uh, and the

attentions of its clients. I couldn't put it any better than that, Robert, But but I feel like we're kind of given normal predators, a normal cannibals a bad name by associating them with with that kind of ghastly you know, very uh, you know, human centric image. That's true. Normal animals, even the ones that sometimes practice cannibalism, are not. Corporations don't decide that hippos are bad now just because occasionally

hippos will eat another hippo, They're still they're hippos. They're animals, they're they're living within an ecology, and they're doing what they have to do to survive. Yeah, I mean, it's like with mice and hamsters and so forth. You know, it's like you can if you get one as a pet and you in your you end up tricking yourself or falling into this idea of thinking them it's like tiny furry people and you're a little furry friend that

lives in this box and scurries around. And then but then if you're going to become horrified when they engage in something in humans such as cannibalizing their young, uh, And that's I mean, you should take that as a learning lesson. You know that this is ah, these are the perils of of anthropomorphizing, uh, the animal world and then then the wild world and the natural order of things. But really, cannibalism is simply ubiquitous and it is going to be practiced by um, you know, most of these

organisms at one point or another. Totally exactly right. Though I want to make clear also I'm not implying that the inverse excuse supplies where you can you can take that logic and apply it back to human institutions like people and like corporations and all that, because come on, they got people in them. People out oft know better. And also we are not condoning human cannibalism, right, that's

what I mean. Yeah, I think you're just talking about the digital media, but neither one neither actually eat killing and eating other humans, nor doing stuff that's akin to cannibalism in metaphorical way right now, Survival cannibalism, that's that's a different scenario. If somebody's already dead and you've got nothing else to live on. Maybe maybe, But then again, like that's that's a decision you're going to have to make in those dire situations. We can't make it for you.

It would be you know, it would just be rude of me to rule on that. I do not know the particulars of your survival cannibalism. So if you are in a survival cannibalism situation right now while listening to this podcast, I cast no judgment. Eat your earbuds. If that that's what you should do, well, maybe if you chew on the earbuds a little, it can distract you. Right, It's kind of like sucking on a button if you're thirsty, right, the I don't know if that actually works, but that's

the old wives tale, right. This has been a lot of fun, Robert, Yeah, another page in the book of Cannibalism. Uh. Likewise, with a lot of these topics, there's so much more we could discuss, and cannibalism will probably come back around to cannibalism again, either generally or you know, regarding a specific organism at some point in the future. Uh. Also, I want to stress again that Bill shoot book Cannibalism

is excellent. Do pick it up. You wrote another one on vampires dealing with vampiric organisms, and that too is an excellent read. So either of those books are wonderful if you want to, like I guess you know, slightly uh slightly ghastly um biological read, They're they're great books. In the meantime, if you want to check out more episodes of Stuff to Blow your Mind, heading over to stuff to Blow your Mind dot com. That's where you'll

find them. That's where you find links, oute of social accounts. That's where you will find a tab for our store where you can buy some merchandise. But if you want to help the show out, the best thing you can do is to rate and review us wherever you have the power to do so, and subscribe. Subscribe to Stuff to Blow Your Mind subscribe to Invention as well. Uh, that's the other show that Joe and I do. It

is an invention by invention, look at human techno history. Recently, we've been spending a lot of time talking about photography and now we're getting into the realm of motion pictures, but in exactly the opposite direction. I've just had in mind a very ancient invention that I want to go back too soon. So so just keep that in mind as a tease ancient superweapons. Yeah, absolutely huge, Thanks as always to our excellent audio producers Alex Williams and Tory Harrison.

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