Speaker 1: Welcome Stuff to Blow your Mind, a production of I
Speaker 1: Heart Radios How Stuff Works. Hey, are you welcome to
Speaker 1: Stuff to Blow your Mind? My name is Robert Lamb
Speaker 1: and I'm Joe McCormick. And no, you're beating around the bush.
Speaker 1: It looks like cannibalism is on the roster for today.
Speaker 1: That's right, And I just want to remind everybody that
Speaker 1: we're not going to be talking about a hannibal lecter.
Speaker 1: This is not a show about like modern cannibalism among humans.
Speaker 1: This is not the Dahmer cast exactly. This is mostly
Speaker 1: going to deal with animals, and towards the end of
Speaker 1: the episode, we are going to discuss some some of
Speaker 1: the questions surrounding cannibalism among ancient humans. But again, if
Speaker 1: it don't worry, We're not going to be talking about
Speaker 1: like like true crime cannibalism here. That's your thing. There's
Speaker 1: plenty of that out there, you know where to find it,
Speaker 1: that's right. So we we've frequently discussed predation on the show,
Speaker 1: and we've of course discussed cannibalism as well. You know,
Speaker 1: we've talked about how it factors into any given organism, organisms, life,
Speaker 1: whether it's predator or prey, as well as its role
Speaker 1: in human evolution. And I think we've also tried. I mean,
Speaker 1: obviously it can be fun to talk about, especially grizzly
Speaker 1: predatory practices in the wild, especially among like invertebrates, But
Speaker 1: I feel like we tried to do our best to
Speaker 1: dispel predator hatred, right. We We did a whole episode
Speaker 1: a while back about why predators are so beneficial for
Speaker 1: ecology and even for for human civilization. Absolutely, and you
Speaker 1: can't look at predators just as the villain of any
Speaker 1: given peace, no matter how dramatic the music and a
Speaker 1: given nature documentary might be. That's something I found watching
Speaker 1: just so many nature documentaries with my son, is that
Speaker 1: earlier on he would get a little wigged out by
Speaker 1: scenes of predation or pending predation because they just have
Speaker 1: such overly dramatic music and they're really playing into the
Speaker 1: idea that the predator is the villain. Yeah, but I'm
Speaker 1: I'm happy to say that he is. He's really gotten
Speaker 1: out of that. It's very rare now that at age
Speaker 1: he just turned seven. Uh, it's very rare that he'll
Speaker 1: be wigged out by predation scene. In fact, there will
Speaker 1: be scenes where say, like some young lions or ripping
Speaker 1: apart of water buffalo or something, and I'll be a
Speaker 1: little wigged out. I'm like, this is getting kind of bloody,
Speaker 1: and I'm like, you sure you wanna finish watching this scene.
Speaker 1: He's like, oh, yeah, it's cool that they're hungry. No, no,
Speaker 1: he's not. He's not bloodthirsty for it. But he he
Speaker 1: has he's already has his appreciation that. Yeah, those those
Speaker 1: animals are hungry. They need to eat. This is how
Speaker 1: they eat. This is part of the natural order of things. Yeah,
Speaker 1: that's really cool. I mean it's it's a hard thing
Speaker 1: to appreciate because of course, within a human context, if
Speaker 1: you see like one human chasing after another human trying
Speaker 1: to hurt him, we know that's morally bad. That's something
Speaker 1: to to oppose. When you see a predator chasing prey, Yeah,
Speaker 1: the prey is fighting for its life, but the predators
Speaker 1: also fighting for its life. It's just obeying its instinct.
Speaker 1: That's part of what it does. And if if the
Speaker 1: predator doesn't get some prey, it too will die. Yeah,
Speaker 1: a wrong move on the on the part of a
Speaker 1: predator giving chase could lead to its death as well.
Speaker 1: Via via starvation, if it were to say, in draw leg.
Speaker 1: But of course, one of the strangest forms of predation
Speaker 1: and one that often seems to even when you see
Speaker 1: it among animals, even when you know better. One that
Speaker 1: I think still strikes many people as a kind of
Speaker 1: taboo or a kind of violation is when predation is
Speaker 1: turned inward on one's own kind, when it turns into cannibalism. Yeah,
Speaker 1: and we've and we've again we've discussed cannibalism on the
Speaker 1: show before, especially sexual cannibalism, I think more recently, Yeah,
Speaker 1: we did a whole episode on sexual cannibalism, especially as
Speaker 1: it appears like among arachnids, in which there are some
Speaker 1: fascinating behaviors. It's far more complex and interesting than just
Speaker 1: like well, male spider mates with a female spider and
Speaker 1: then the female eats the male. They're all kinds of
Speaker 1: economic energy dynamics going on different behavioral adaptations to that,
Speaker 1: to that kind of world. It's a really truly complex
Speaker 1: and interesting subject. Yeah, And I think economics is the
Speaker 1: way I always try and and and focus on it,
Speaker 1: you know, just thinking of just the the economy of uh,
Speaker 1: turning sunlight into flesh, which is basically what happens with
Speaker 1: the food chain. And so you're going to reach a
Speaker 1: point where even another member of your own species is energy.
Speaker 1: And what are you to do if you are, say
Speaker 1: a scorpion or something. I mean, especially with the with
Speaker 1: the scorpion, which is you know, UM tends to be
Speaker 1: a solitary organism. Uh, you know you're not going to
Speaker 1: let that energy just go to waste because you have
Speaker 1: some sort of you know, heightened scorpion morality or you know,
Speaker 1: our ethical system in play. No, you're gonna you're gonna
Speaker 1: show down on some cannibal meat. Well, no, again, animals
Speaker 1: are not humans. We with human brains can appreciate reasons
Speaker 1: that one should not eat one's own kind. Yeah, but
Speaker 1: if in the rest of the animal animal world cannibalism
Speaker 1: is widespread. So I today's episode, you know a lot
Speaker 1: of what we're gonna deal with this this idea of
Speaker 1: almost cannibals, which is something I started thinking about while
Speaker 1: I was vacationing in Belize. I was out there with
Speaker 1: the family, snorkeling, and I was slipping through a guide
Speaker 1: book for Caribbean organisms um aquatic organisms, and I came
Speaker 1: across a couple of entries for the head shield slug. Okay,
Speaker 1: this is kind of like a it looks sort of
Speaker 1: like a hammerhead slug. Yeah, it looks like a hammer
Speaker 1: head sea slug. They're also known as bubble snails um
Speaker 1: and and these are members of the clade um Cephalospidia,
Speaker 1: and the these names head shield slugs bubble snails. The
Speaker 1: name refers to their common head shield, as is a
Speaker 1: broad head that's used for burrowing in the sand and
Speaker 1: it helps to keep the sand out of their mantle cavities.
Speaker 1: And most have have shells, but some species have have
Speaker 1: to have a reduced shell and some have what's known
Speaker 1: as a like a bubble shell. Now I never got
Speaker 1: to actually see one while snorkeling, but the two entries
Speaker 1: in the book, I got my my mind working because
Speaker 1: there was leech head shield slug, which was this beautiful
Speaker 1: dark blue indigo creature with bright yellow stripes. This is
Speaker 1: one of the counterintuitive things about nature, is that clearly
Speaker 1: one of the most beautiful types of animal in the
Speaker 1: entire world or sea slugs. Yeah, yeah, absolutely, uh. But
Speaker 1: then there was another one. There was the mysterious head
Speaker 1: shield slug. That's what it's called that was in in
Speaker 1: this in this book, and this may have been an
Speaker 1: older book. There may be updated names for some of
Speaker 1: these now, but this one looked had the color of
Speaker 1: just rotting vegetation swearing camo. And as for their diets,
Speaker 1: the book listed that the mysterious head shield slug feeds
Speaker 1: on other sea slugs, especially the the lettuce sea slug. Okay,
Speaker 1: fair enough, right, there are a lot of sea slugs
Speaker 1: out there, and there's a lot of competition in aquatic environments. Um,
Speaker 1: you know, we're dealing with a very large subclass of
Speaker 1: the gastropod of family here. But the leech head shield
Speaker 1: slug its diet was listed as other head shields, So
Speaker 1: it's getting even closer to home, right, Yeah, so it's
Speaker 1: not cannibalism. You know, they're not the same species. Uh,
Speaker 1: they're in the same family, but I suppose, you know,
Speaker 1: it's it's the name that that gives me pause. The
Speaker 1: fact that they're both classified as headshield slugs. Well, that
Speaker 1: is a kind of interesting question to say, Like, Okay,
Speaker 1: we know cannibalism happens pretty often in the wild, and
Speaker 1: we'll discuss the conditions and just a minute here, there
Speaker 1: are some limitations that are imposed by genetics, by the
Speaker 1: energy economy, and by epidemiology on on how far you
Speaker 1: can go with practicing cannibalism as a lifestyle as an animal.
Speaker 1: Uh So they these limitations are in place. Some of
Speaker 1: those limitations might not be in place if you're preying
Speaker 1: on something that's a lot like you, but is not
Speaker 1: exactly you. Right, So, yeah, that's something we're going to
Speaker 1: talk about here. You know, what are some examples of
Speaker 1: um near cannibalism, Like what are some of the more
Speaker 1: closely related prey predator relationships out there in the animal world?
Speaker 1: And then what does that say about us? What does
Speaker 1: that say about the way that humans think about cannibalism?
Speaker 1: In a weird way, this episode topic even got me
Speaker 1: thinking about some of the strange economic dynamics of digital media.
Speaker 1: I promise that's not as boring as it sounds. We'll
Speaker 1: come back to that later. I don't know, digital media cannibalism.
Speaker 1: That sounds pretty exciting and probably just like spot on
Speaker 1: and just a fact of life. So let's refresh a
Speaker 1: little bit about cannibalism. So, to eat one's own species
Speaker 1: is to commit an act of cannibalism. Now, sometimes especially
Speaker 1: we'll get into a few cases later on. Sometimes this
Speaker 1: word we the word cannibalism is used for things that
Speaker 1: are not quite cannibalism. But that's where we get into
Speaker 1: that gray area of near cannibalism. Yeah, and it's sometimes
Speaker 1: said with the derogatory context, but I mean again, it's
Speaker 1: something that like, obviously, if you kill and eat your
Speaker 1: next door neighbor, that's a bad thing. But animals this
Speaker 1: is just sometimes an adaptation that animals have, that's right.
Speaker 1: And there are many different varieties and classifications we've discussed.
Speaker 1: Somebody's done the show before. Sexual anibalism for instance, which
Speaker 1: like you said, can be can be, you know, rather complex.
Speaker 1: It's not just a situation of well I made it
Speaker 1: with him, I guess now I'll consume his flesh. A
Speaker 1: lot of times it depends on, for example, what the
Speaker 1: male brings to the table in the sexual encounter. There
Speaker 1: are some species of spider where if a male shows
Speaker 1: up with a food gift for the female, for example,
Speaker 1: he can he can be more likely to avoid being
Speaker 1: cannibalized after mating, whereas if he shows up and just
Speaker 1: wants to mate and doesn't bring her anything to snack on.
Speaker 1: He's more likely to be cannibalized. And this sort of
Speaker 1: makes sense, right, like or is he is he contributing
Speaker 1: additional food resources to the development of the offspring? Right?
Speaker 1: And then there are other examples like matrophagi where babies uh,
Speaker 1: where the offspring consume the mother um. You know, they're
Speaker 1: they're examples where um of a mother organism will consume
Speaker 1: the young. And a lot of these cases of cannibalism
Speaker 1: in the while, they're they're going to be influenced by uh,
Speaker 1: you know, economic um uh resource uh deprivation issues like
Speaker 1: are those offspring going to survive? Is something threatening them?
Speaker 1: Should then the energy of those uh of the offering
Speaker 1: be uh brought back into the host or into the
Speaker 1: mother organism. Yeah, Now, I detect among the literature in
Speaker 1: in zoology and behavioral ecology and all that that there
Speaker 1: there's been a shift in consciousness about cannibalism over the
Speaker 1: previous decades where I think it used to be more
Speaker 1: common for scientists to believe that cannibalism would was something
Speaker 1: animals would only do under extreme scenarios, like if they
Speaker 1: were in a starvation scenario, you know, just like the
Speaker 1: absolute limits of survival, and that has increasingly it's increasingly
Speaker 1: become clear that that's not the case. Though animals don't,
Speaker 1: you know, they're not usually going to practice cannibalism as
Speaker 1: some kind of primary mode of living. There are actually
Speaker 1: a pretty wide range of scenarios in which cannibalism occurs,
Speaker 1: and we're we're documenting more and more of those scenarios
Speaker 1: all the time. It's not always just star ovation at
Speaker 1: the very edge of survival and the peaks of stress. Yeah.
Speaker 1: So it's one of these things that is, you know,
Speaker 1: we're learning as ubiquitous in the natural world. It it
Speaker 1: offers some really key advantages, though there are some downsides.
Speaker 1: It remains highly popular without ever becoming like the thing
Speaker 1: right like you made your species might engage in cannibalism
Speaker 1: for a number of different reasons, but you were not
Speaker 1: going to become an obligate cannibal like that is where
Speaker 1: the system would collapse. Yeah, and I think there are
Speaker 1: some reasons that that's sort of impossible. I'll talk about
Speaker 1: that in just a minute. It reminds me a lot
Speaker 1: of some things I've heard about the band Primus. I've
Speaker 1: heard stuff, but okay, well I'm going with you. I'm
Speaker 1: not saying that the members of Primus are cannibals, but
Speaker 1: rather um, I think it was less Claypool himself, who
Speaker 1: at one point pointed out that like they were in
Speaker 1: a good place popularity wise, like they like they never
Speaker 1: completely went out of fashion, but at the same time,
Speaker 1: like they never just really blew up. Like I feel
Speaker 1: like most people, Uh, if you asked them, they might say, oh, yeah,
Speaker 1: Primus is cool. I did Primus. I myself have enjoyed
Speaker 1: a prime Primus in concert before, but I would I
Speaker 1: would never say Primus is necessarily my favorite band. Uh. Likewise, cannibalism,
Speaker 1: It's okay, I'm with you. I see what you're saying. Yeah,
Speaker 1: I mean, yeah, they're Primus has long been By the way,
Speaker 1: my candidate for what I joke about is like the
Speaker 1: least sexy or least romantic possible music. So if you're
Speaker 1: trying to like figure out what to put on for
Speaker 1: a Valentine's Day dinner or something like that, so you
Speaker 1: could go with like your Marvin Gay or you know,
Speaker 1: your classic romantic options, and at the other end of
Speaker 1: the spectrum you've got Primus. Yeah. For me, Primus is
Speaker 1: more like driving around music, you know it nothing will
Speaker 1: scribe if you if you were thirsting for primus, nothing
Speaker 1: else will do. But then there are plenty of other
Speaker 1: cases where it probably is not going to be the
Speaker 1: ideal soundtrack for life. But anyway back back to canalism,
Speaker 1: So yes, there it can be especially useful in certain
Speaker 1: ecological situations. Uh and and there are a lot of
Speaker 1: key benefits to the individual. On the other hand, it
Speaker 1: can impact community dynamics. But the exact shape and scope
Speaker 1: of a species cannibalism it varies greatly. Yeah, exactly. Um So,
Speaker 1: so there are these obvious, like you're talking about, economic
Speaker 1: and evolutionary limits on what forms cannibalism can take, even
Speaker 1: though it can to each individual animal that practices that
Speaker 1: give all kinds of benefits. One example would be that
Speaker 1: you know, when one species regularly eats another species, it
Speaker 1: is common that the prey species is in some way
Speaker 1: more vulnerable, it's smaller or weaker, definitely more numerous than
Speaker 1: the predator species. You can't make a diet out of
Speaker 1: eating mostly or entirely animals that are say as good
Speaker 1: at killing you in self defense as you are at
Speaker 1: killing them in predation or the economics of acquisition. Just
Speaker 1: don't work out, right, You're not gonna go chasing down
Speaker 1: something that's got all the same muscles and teeth and
Speaker 1: claws and all that as you. Right, you have to
Speaker 1: have some sort of an advantage, either a direct biological
Speaker 1: advantage or some sort of behavioral advantage such as pack
Speaker 1: hunting or something like that. But but even in those
Speaker 1: cases it can be exceedingly risky. And and think again,
Speaker 1: how I mean, I think we sometimes because we have
Speaker 1: medical care, we uh downplay the risks to an animal
Speaker 1: in the wild of a mirror like you know, leg
Speaker 1: injury or something like that, which can be fatal to
Speaker 1: an animal in the wild, while you know, you can
Speaker 1: just go to the hospital and get fixed up. So
Speaker 1: if adults of a species focus on other similarly sized
Speaker 1: adults of the same species, hunting probably becomes too dangerous
Speaker 1: to sustain as a regular practice. Also, a species cannot
Speaker 1: make a diet out of eating mostly or entirely animals
Speaker 1: that are less numerous than itself, because it's going to
Speaker 1: run out of food and starve, or it's gonna have
Speaker 1: to switch to a different food source. If an animal
Speaker 1: were to eat primarily or entirely members of its own species, Uh,
Speaker 1: there would immediately be a couple of problems. And number one,
Speaker 1: you would have to think, if it's a sexually reproducing species,
Speaker 1: this behavior is probably going to interfere with mating and
Speaker 1: lead to depletion of mates. Probably more importantly, the species
Speaker 1: couldn't survive. It would sort of eat itself to extinction.
Speaker 1: Like if every member of the species needed to eat
Speaker 1: one other member of the species every month in order
Speaker 1: to not starve to death. Your best case scenario is
Speaker 1: having the number of individuals every month. Now, maybe you
Speaker 1: think you could replace those through rapid reproduction, but where
Speaker 1: does the energy to create and grow those new bodies
Speaker 1: come from unless you're eating even more of your own kind.
Speaker 1: So it seems kind of I was trying to find
Speaker 1: an example of something that comes close, but it seems
Speaker 1: to me you can't really have something like an obligate
Speaker 1: cannibal species, something that only eats its own kind. That
Speaker 1: seems like an an absurdity. So you have that fact,
Speaker 1: but then you also have the fact that we do
Speaker 1: observe lots of in species cannibalistic behavior in the wild
Speaker 1: in the wild, and we know that this can only
Speaker 1: take place in sort of limb did conditions and scenarios,
Speaker 1: and we're discovering more and more of those types of
Speaker 1: scenarios all the time. Here's a common one we know.
Speaker 1: You can't just eat members of your own species for
Speaker 1: your entire diet and have every member of your species
Speaker 1: do this for your entire life, for the species would
Speaker 1: cease to exist. But within certain phases of life, cannibalism
Speaker 1: can be a primary strategy. Consider the larval stage of
Speaker 1: many amphibians. Uh you have like cannibal morph larvae of
Speaker 1: tiger salamanders. We talked about those in our episode on
Speaker 1: salamanders with Mark Mandica. Or think about the cannibalistic tadpoles
Speaker 1: of toad species like the spadefoot toad. And this is
Speaker 1: where the biggest tadpoles in a small body of water
Speaker 1: will eat the smaller ones to survive and grow even bigger.
Speaker 1: It's sort of like a letting letting the strongest of
Speaker 1: the of the litter absorb the energy of all the others. Now,
Speaker 1: obviously this kind of strategy can't be continued for the
Speaker 1: amphibians entire life cycle, but it can work in a
Speaker 1: phase of the life cycle because the other energy inputs
Speaker 1: into that phase. Another great example from another episode we
Speaker 1: had with a with a guest was thinking about intra
Speaker 1: uterine cannibalism in some sharks species, like we talked about
Speaker 1: with Mara Hart, where some unborn sharks will swim over
Speaker 1: and eat their siblings or half siblings before they even
Speaker 1: leave their mother's uterus. Do we talk about cannibalism with
Speaker 1: all of our guests? I don't know. It does seem
Speaker 1: to come up a good fit, but maybe we do.
Speaker 1: I don't think we brought either of these up, did we.
Speaker 1: I mean, I guess they were just an innate part
Speaker 1: of the cut, the conversation and the expertise of the guests.
Speaker 1: Maybe we just invite creepy guests. They're not creepy. Maybe
Speaker 1: we're creepy. We're talking about cannibalism right now. We're definitely creepy.
Speaker 1: So while cannibalism can't be the entire diet of a species,
Speaker 1: it can be an important supplemental part of a diet,
Speaker 1: especially in scenarios of environmental stress, and it can even
Speaker 1: reduce competition when times are tough. One example here is
Speaker 1: that cannibalism, according to what I've read, it's much more
Speaker 1: common if you live life in the water. Oh, yes, definitely. Yeah,
Speaker 1: if you're wet, you're probably involved in cannibalism in some way.
Speaker 1: It just happens a lot more in aquatic environments. For example,
Speaker 1: when fish are foraging for food, one type of energy
Speaker 1: source they will often come across is little sphere ules
Speaker 1: of lipids and energetic materials floating in the water. Other
Speaker 1: fish eggs. Uh. These fill the waters of the ocean
Speaker 1: by the bazillions, and this will include some eggs of
Speaker 1: their own species, which they basically just eat discriminately along
Speaker 1: with the other eggs. We recently did the episode on
Speaker 1: the Christmas Island crabs. Oh, yeah, where they just stuff
Speaker 1: the crabble are right into their mouths. Yeah, I mean,
Speaker 1: how do you know if it's your own offspring. Chances
Speaker 1: are it's not. There's so many out there, it's probably
Speaker 1: somebody else's. Also, I think I accidentally said that they
Speaker 1: will eat them discriminately. Obviously they eat them indiscriminately, is
Speaker 1: what I mean. Fish don't discriminate. But yeah, it works
Speaker 1: out because fish produce a lot of eggs. Under the
Speaker 1: evolutionary assumption that most of the eggs, many of the
Speaker 1: eggs at least, will not survive and the eggs of
Speaker 1: one's own species are only a supplemental part of the
Speaker 1: adult fishes diet, not the whole thing for the whole species,
Speaker 1: which again would be a problem. But the phenomenon of
Speaker 1: adults eating young of their own species actually happens in
Speaker 1: many scenarios outside the water too. Obviously, it would make
Speaker 1: no sense for animals to have instincts to kill and
Speaker 1: eat all of their own young, but there is some
Speaker 1: selective strategic snacking of this kind. Like often rodent mothers
Speaker 1: will eat some of their own litters, especially those that
Speaker 1: are sickly or don't seem like they're gonna thrive. Male
Speaker 1: carnivores like lions, will sometimes eat the cubs sired by
Speaker 1: another male, and this tends to increase the female lions
Speaker 1: receptivity to mating and the pride. Yeah, this is seen
Speaker 1: in bears as well, for sure. Oh yeah, definitely. And
Speaker 1: then there are some really strange cases that were observing
Speaker 1: again more and more all the time, even with animals
Speaker 1: once thought to be herbivores engaging in occasional cannibalism. Here's
Speaker 1: when I came across hip pose what hundred percent herbivores right, Well,
Speaker 1: that this one one I always assumed. I mean you
Speaker 1: hear to hear about like the vast amount of vegetation
Speaker 1: that a given hippo needs to consume, and that is
Speaker 1: their primary diet. They mostly are herbivores, but occasionally they'll
Speaker 1: just be versatile. So we used to think there are
Speaker 1: a hundred percent herbivores. They're mostly herbivores, except now it's
Speaker 1: been observed that sometimes they'll kill and eat an impula,
Speaker 1: or even sometimes they will eat a fellow hippopotamus. Well,
Speaker 1: they are ferocious. I mean, we can't take that away
Speaker 1: from them. So there are just more and more examples
Speaker 1: all the time that science is documenting about ways that
Speaker 1: animals will occasionally or opportunistically or even in some controlled ways,
Speaker 1: regularly engage in direct in species cannibalism. Yeah. I was
Speaker 1: reading the amazingly titled two thousand tin paper Cannibals in Space,
Speaker 1: the Coevolution of Cannibalism and Dispersal in spatially structured Populations
Speaker 1: and U. And in this the authors point out that
Speaker 1: the propensity for cannibalism, you know, it's going to vary
Speaker 1: considerably among even closely related species. And then a lot
Speaker 1: of questions remain concerning exactly what drives variation and the
Speaker 1: evolution of cannibalism across and even within a species, and
Speaker 1: the can and the same can be said for the
Speaker 1: evolutionary consequences of cannibalism. Yeah, a lot about cannibalism remains
Speaker 1: an open question. There's still a ton we don't know.
Speaker 1: But I think one thing that is emerging is what
Speaker 1: we're getting some good ideas of what the major downsides
Speaker 1: to cannibalism are, like, what are the limitations that are
Speaker 1: imposed on it as a practice, And so I want
Speaker 1: to mention I think three major ones that there may
Speaker 1: be other ones, but these are three major ones. One is,
Speaker 1: if you're practicing cannibalism, you could end up eating animals
Speaker 1: closely related to you. And given the self preserving tendencies
Speaker 1: of genes and evolution, there's going to be a selection
Speaker 1: pressure against this. Genes will tend to come about and
Speaker 1: become prevalent within the species that say don't eat each
Speaker 1: other if you have this gene. Also, as we mentioned
Speaker 1: are here, it's a risky to try to kill and
Speaker 1: need an animal that has ald the same equipment you do,
Speaker 1: the teeth, the muscles, the fighting abilities, it's easier to
Speaker 1: go after weaker prey, and there's usually some kind of
Speaker 1: weaker prey out there. But there are ways around both
Speaker 1: of these. I mean, for one thing, you can try
Speaker 1: to avoid eating animals you're closely related to, even if
Speaker 1: you're eating your own species, by evolving ways of detecting relatedness.
Speaker 1: So maybe you know there's some gene that allows you
Speaker 1: to recognize who is your from your immediate family and
Speaker 1: not eat them. I actually have an example of this.
Speaker 1: We'll come back to that later. Okay. Another thing you
Speaker 1: can get around is that animals with cannibalistic tendencies can
Speaker 1: get around the problem of fighting uh something, fighting something
Speaker 1: just as big and dangerous as as you are by
Speaker 1: eating smaller, weaker con specifics. And this can take the
Speaker 1: form of sexual cannibalism, like in some spiders like the
Speaker 1: red back spider, where there's a huge difference in size
Speaker 1: between the males and females and it works out just
Speaker 1: fine for the females to eat the males after mating,
Speaker 1: or this can happen with adults preying on larvae or
Speaker 1: smaller juveniles of their own species. But finally, one last
Speaker 1: big problem with cannibalism, and we'll come back to this.
Speaker 1: When you eat your own kind, you put yourself at
Speaker 1: risk of catching diseases and parasites. You're more likely to
Speaker 1: consume or otherwise expose yourself to something bad that can
Speaker 1: infect your species. If you're eating animals that are already
Speaker 1: of your own same species, Yeah, you're basically diving into
Speaker 1: a swimming pool of this other individual's potential viruses and illnesses.
Speaker 1: You're you're diving into a swimming pool marked bio hazard. Yeah.
Speaker 1: So there's always a cost benefit calculation going on. And
Speaker 1: I'm not saying obviously that the animals are doing this
Speaker 1: calculation consciously in their heads, but somehow this calculation is
Speaker 1: being worked out. There benefits to cannibalism, there's an obvious
Speaker 1: energy advantage, and there are all these downsides, And so
Speaker 1: the circumstances and and the specific traits of each individual
Speaker 1: species are going to interact to determine when cannibal is
Speaker 1: m is actually appropriate. Alright, Well, on that note, we're
Speaker 1: going to take a quick break, but when we come back,
Speaker 1: we're gonna continue exploring this topic. And we're going to
Speaker 1: kick off by discussing this idea of near cannibalism a
Speaker 1: little bit more than thank you. All right, we're back.
Speaker 1: So we were just talking about the limitations, Uh, well,
Speaker 1: all of the examples we see of cannibalism in the
Speaker 1: natural world, true cannibalism where members of one animal species
Speaker 1: are eating members of the same animal species. Uh. And
Speaker 1: then limitations on wind cannibalism can be practiced, and what
Speaker 1: what might hold it hold it at bay from becoming
Speaker 1: too prevalent. But there are probably examples of animals doing
Speaker 1: something that is not quite cannibalism, but where they're eating
Speaker 1: something that's kind of close to them. Yeah, And so
Speaker 1: I started looking around for answers on this, and one
Speaker 1: thing that that did come up when I was looking
Speaker 1: for near cannibalism and um and you know, scholars, scholarly
Speaker 1: works and academic papers, I ended up running across it
Speaker 1: in some myth papers on myth and medieval histories. And
Speaker 1: I found this rather telling, not so much about like
Speaker 1: what's going on in the animal kingdom, but about like
Speaker 1: why I'm fascinated with it, Why this idea of near
Speaker 1: cannibalism is perhaps even a little more interesting than interesting
Speaker 1: to me compared to apps absolute cannibalism. So For instance,
Speaker 1: there are medieval accounts of the Danes roasting animal flesh
Speaker 1: to eat alongside, like right next to heaped the heaped
Speaker 1: human dead from a battle, so like feasting on the
Speaker 1: battle grounds with their slain enemies around them, almost sort
Speaker 1: of suggesting a mental connection. Uh yeah, And of course,
Speaker 1: again these are accounts of the Danes probably you know,
Speaker 1: with it with the idea of portraying them as being
Speaker 1: in the state of of near cannibalism, Like look at that,
Speaker 1: they're just cooking their meat right next to the bodies
Speaker 1: of the dead. They're just there's just one misstep away
Speaker 1: from going full cannibals. Romans would never do anything like that.
Speaker 1: Another thing that come up came up with was the
Speaker 1: myth of like Cayan, which we recently discussed, and there's
Speaker 1: an act of near cannibalism cannibalism there as well, where
Speaker 1: the flesh of a human is offered up to the
Speaker 1: god Zeus to say, like, hey, Zeus, do you want
Speaker 1: to eat some human flesh? Like they're trying to trick Zeus. Uh. Now,
Speaker 1: granted Zeus humans a god, but sort of yeah, I
Speaker 1: mean it seems like species enough, like if if if
Speaker 1: the gods of Greek mythology can mate with humans. It
Speaker 1: seems like that they should be like biologically close enough
Speaker 1: that eating us would be a cannibalism, right right. And
Speaker 1: of course you know the gods, especially the Greek gods,
Speaker 1: they were down for any number of horrible acts. They
Speaker 1: would turn into an animal to mate with a human,
Speaker 1: that sort of thing. But I guess the thing is
Speaker 1: that they probably are not going to look kindly on
Speaker 1: being tricked into doing anything vile that they didn't want
Speaker 1: to do. No, And of course when Zeus was almost
Speaker 1: tricked into eating human flesh, he retaliated. By their different
Speaker 1: tellings of the story, sometimes he retaliates by just like
Speaker 1: killing a bunch of people. Sometimes he retaliates by turning
Speaker 1: the king who tried to trick him into a were wolf,
Speaker 1: has pointed out by seed down him in the Good,
Speaker 1: the Bad, and the Ugly portrayals of Vikings in the
Speaker 1: Fragmentary Animals of Ireland, near cannibalism and near paganism were
Speaker 1: considered the apotheosis of the evil. Yeah, you see this
Speaker 1: in many ancient sources. It's like cannibalism is sort of
Speaker 1: held out as it's it's the archetype of barbarism. You know,
Speaker 1: it's like the ultimate act that in itself in an
Speaker 1: iconic way shows that somebody is not civilized and not good.
Speaker 1: And there's something as he's pointing out her, there's something
Speaker 1: tantalizing about like that that that moment before cannibalism, that
Speaker 1: or that moment before paganism, like that slip that decline
Speaker 1: into this barbarous nature. Uh, the idea that, oh, they're
Speaker 1: not cannibals now, but I bet they'll be cannibals tomorrow
Speaker 1: because look what they're doing right now. And of course, uh,
Speaker 1: in the animal king um, all these species we're you know,
Speaker 1: we're looking at cannibalism is already in the blueprint, like
Speaker 1: it's already part of the of the of the act.
Speaker 1: But there is there's something about about about that to
Speaker 1: the the human mind, I think, you know, because we
Speaker 1: can't help to think of of of all of these
Speaker 1: changes taking place not against the the in in the
Speaker 1: time scale of evolutionary history, but we think about it
Speaker 1: within the terms of lifespan and the choices that we make.
Speaker 1: But anyway back back to just like purely the the
Speaker 1: animal world here I did can run across a study
Speaker 1: that points at a possible case of cannibal fueled speciation,
Speaker 1: because I think that's something to interest to think of,
Speaker 1: because it's like if I'm if if one if within
Speaker 1: a species, members of that species are deciding to just
Speaker 1: go full cannibal like they're like, oh, I can just
Speaker 1: eat my own species all the time. If that were
Speaker 1: to happen, could that conceivably lead to a speciation event
Speaker 1: where the cannibals become their own species. Oh yeah, that's
Speaker 1: an interesting question. And so this this study I found
Speaker 1: in two thousand seventeen study, and I should stress that
Speaker 1: this is an unrefereed preprint in bio archive, so caveats
Speaker 1: on not going through peer review, right. But in it,
Speaker 1: the author's point to cannibalism in South American um annual
Speaker 1: killie fish that's austro lebias as a possible speciation event.
Speaker 1: So they're they're they're presenting what they refer to as
Speaker 1: an alternate hypothesis for giant dwarf speciation where where some
Speaker 1: of these uh we're basically the chilly fish here have
Speaker 1: evolved in sympathy without geographic separation by character displacement and
Speaker 1: cannibalism but in this day, the authors are discussing cannibalism
Speaker 1: in South American annual killie fish, and the idea here
Speaker 1: is that it could it could be a speciation event
Speaker 1: going on here, that that accounts for giant dwarf speciation,
Speaker 1: So basically bigger, bigger killy fish versus a smaller chilly fish,
Speaker 1: and cannibalism could play a role in that right right there,
Speaker 1: That that could be what's what's pushing this species into
Speaker 1: two species based on the size of the individuals. Yeah,
Speaker 1: that's interesting if I am understanding their argument correctly. Okay, Now,
Speaker 1: there's one thing that I had been thinking about as
Speaker 1: a potential case of near cannibalism, which we've already sort
Speaker 1: of discussed in a previous episode called Strange Milk. So
Speaker 1: I won't linger on it too long. This has come
Speaker 1: up before, but I just wanted to remind us of
Speaker 1: one form of feeding that could be seen as analogous
Speaker 1: to cannibalism, but without the element of lethal predation, and
Speaker 1: that is found in various systems where an adult animal
Speaker 1: feeds its offspring with some part of its own body. Ah. Yes,
Speaker 1: so this is not predation. The offspring does not necessarily
Speaker 1: kill and eat the adult, but it could be considered
Speaker 1: a form of alternative cannibalism, as if I could like
Speaker 1: off one of my arms and feed it to my kids. Interesting,
Speaker 1: and the great example here is the type of amphibian
Speaker 1: known as Sicilians. Now it's not spelled like from Sicily.
Speaker 1: It's c A E C I L I A N.
Speaker 1: Sicilians are amphibians. They're kind of like frogs and salamanders,
Speaker 1: but they've got no legs. They look like a cross
Speaker 1: between a snake and a worm, like a like a
Speaker 1: wet earth snake. They tend to live underground, so we
Speaker 1: rarely see them, and if you do see one, you
Speaker 1: might mistake it for some kind of gigantic worm. Yes,
Speaker 1: I remember we we talked about about the about the
Speaker 1: Sicilians with Mark Pendina. Oh yeah. And one of the
Speaker 1: things we talked about with the Sicilians and the strange
Speaker 1: Mailk episode was that after the mother of a Sicilian
Speaker 1: species called a boo Langarula titan us gives birth, she
Speaker 1: turns her outer skin into a nutrient rich secretion for
Speaker 1: her offspring, and then the young gross special teeth. I've
Speaker 1: seen these referred to as shaped a slotted spoon so
Speaker 1: that they grow special teeth, uh quote, which they used
Speaker 1: to peel and eat the outer layer of their mother's
Speaker 1: modified skin. And that's a quote from a two thousand
Speaker 1: six paper in Nature. So basically, the mother turns her
Speaker 1: skin into like this cheese like substance, and then the
Speaker 1: juvenile worm like creatures chew off their mother's skin. They
Speaker 1: peel her like a like a vegetable. This is interesting.
Speaker 1: This is it's very it's consensual. It's it's not just
Speaker 1: a situation where the young eat the mother, but the
Speaker 1: mother is mother said is essentially saying, here, take of
Speaker 1: this specially prepared skin and eat it in remembrance of me. Yes,
Speaker 1: take of my body and take of my skin. I mean.
Speaker 1: It seems to combine multiple elements of the Texas Chainsaw
Speaker 1: Massacre together at once, but somehow without the massacre. So
Speaker 1: there's the peeling of skin, peeling the skin off, and
Speaker 1: a form of near cannibalism, but without the elements of predation.
Speaker 1: The the the willing adults says, try my skin. It's good,
Speaker 1: and they do. That's what we aid for the the
Speaker 1: to to reboot the Texas Chainsaw Massacre franchise is we
Speaker 1: need to we need to take the mascre at mascre
Speaker 1: at just have everything else happening consentually, and ultimately that's
Speaker 1: going to be more terrifying. I think it's just about
Speaker 1: a consensual human barbecue cook from from Texas. Yeah, you know,
Speaker 1: I've had that thought with a few different horror films
Speaker 1: that have come out where you know, they're there, you know,
Speaker 1: people behind them are sometimes pushing the boundaries and they're like,
Speaker 1: and it's all about like horrible things being done to people.
Speaker 1: And I'm and I'm thinking, you know, the creators here
Speaker 1: obviously they think that this is that this is horrible,
Speaker 1: and this is a terrifying vision of of life. But
Speaker 1: but what if what if it what if everyone was
Speaker 1: engaging in it willingly, like you know, then it would
Speaker 1: put an entirely different spin, and arguably a more thought
Speaker 1: provoking and even terrifying spin. I feel like that's often
Speaker 1: what black mirror is. Black mirror is often like a
Speaker 1: what would otherwise be like a horror movie or a
Speaker 1: horror show, except most of the time the people who
Speaker 1: are the victims of whatever is happening in the episode
Speaker 1: get involved consensually. Yeah, because it's technology because the technology exactly. Like,
Speaker 1: for instance, if you had a Friday the Thirteenth film
Speaker 1: where all of the young people went off to camp
Speaker 1: and the thing that they all really hoped for, that
Speaker 1: the thing they desired most of all, was to be
Speaker 1: massacred by the mass killer that runs the woods. You
Speaker 1: know that that would fulfill some sort of deep desire
Speaker 1: in them, some desire for I don't know, like teenage
Speaker 1: martyrdom or something like that. Ultimately, like that that that
Speaker 1: gets me thinking a lot more. There's a sort of
Speaker 1: almost element of that in Hell Raiser. I guess people
Speaker 1: are looking for trouble messing around with a puzzle box.
Speaker 1: They should know better than Yeah, And of course that
Speaker 1: would make sense. Clive Barker, especially in the younger Clive Barker,
Speaker 1: I think he did engage in a lot of a
Speaker 1: lot more subversive treatment of these things. Well, speaking of
Speaker 1: Clive Barker, okay, on that. You know, I thought of
Speaker 1: Clive Barker already earlier in this episode when there were
Speaker 1: a couple of times where you just said flesh and
Speaker 1: I was like, you kind of can't do that without
Speaker 1: saying it in the Doug Bradley voice. Yeah, obviously, we're
Speaker 1: big fans of some of the hell Raizor films, and
Speaker 1: and uh, and I definitely hold up some of Barker's work,
Speaker 1: especially his books of blood short stories. There's some some
Speaker 1: really good short stories in those collections. Yeah, I've always
Speaker 1: meant to read them, might never have yet. But we
Speaker 1: should get back to near cannibalism. Well, let's bring things
Speaker 1: around to the human realm, or at least the you know,
Speaker 1: the the ancient human realm. So let's talk about humans
Speaker 1: and Neanderthals. So evidence has been presented and sometimes dismissed
Speaker 1: regarding regarding cannibalism among both ancient humans. Though it gets
Speaker 1: kind of complicated because we're talking about ancient humans, but
Speaker 1: technically you call these modern humans. They're they're ancient from
Speaker 1: our standpoint, but they are evolutionarily modern humans. So uh,
Speaker 1: at anyway that there's there's their arguments and evidence for
Speaker 1: both these ancient modern humans and the indertal is engaging
Speaker 1: in cannibalism. And as we've discussed on the show before,
Speaker 1: the evidence that scientists look for when they're talking about that,
Speaker 1: they're looking for signs of processing on the bones. In
Speaker 1: other words, it's not enough that a human or a
Speaker 1: neandertal skull was caved in by heavy object, But are
Speaker 1: there signs of the bodies having been systematically or ritually
Speaker 1: stripped of meat or marrow for the purposes of consumption?
Speaker 1: And uh so, so that's one of the things they
Speaker 1: look for. And as Bill Shoot points out in his
Speaker 1: his excellent book Cannibalism, archaeologists generally want to match this
Speaker 1: sort of evidence up with similar damage on the bones
Speaker 1: of game animals from the same site, so that way
Speaker 1: they can say, look, this is what these people were
Speaker 1: doing to the bones of animals that were clearly praise
Speaker 1: a prey species, and here's what was done to the
Speaker 1: bones of other members of the species. And then you
Speaker 1: have more of a direct comparison to make here, so
Speaker 1: that you can say, this looks like this was cannibalism.
Speaker 1: That all makes sense. There's some pretty convincing there's some
Speaker 1: pretty convincing evidence that Neanderthals engaged in cannibalism, at least
Speaker 1: survival cannibalism. And Shoot points out in his book that
Speaker 1: the near Neanderthal species Homo antecessor quote, may have simply
Speaker 1: considered others of their kind to be food, and he
Speaker 1: pointed out. You know that again, this is hardly out
Speaker 1: of step with the rest of the animal kingdom. Cannibalism
Speaker 1: is ubiquitous, so it's not surprising that Neanderthals or Neanderthal ancestor,
Speaker 1: or that Homo sapiens engaged in this practice. But what
Speaker 1: what's interesting us the most for this episode is the
Speaker 1: question of near cannibalism. Right, whether ancient modern humans considered
Speaker 1: Neanderthal's prey or vice versa, how much uh consumption of this,
Speaker 1: of this this other man like creature was going on, this,
Speaker 1: how much near cannibalism was happening. So for starters, we
Speaker 1: have some competing theories, but for the most part, we
Speaker 1: don't know exactly what happened to the Neanderthal. They obviously
Speaker 1: they went extinct, and we know that they likely transition
Speaker 1: from Homo antecessor to Homo Neanderthal plenis about about a
Speaker 1: hundred and fifty thousand years ago, and then they went
Speaker 1: extinct thirty thousand years ago, So that's kind of the
Speaker 1: the period of their existence as far as we understand it.
Speaker 1: One hypothesis is that that's out there is that humans
Speaker 1: in the Neanderthals interbred and that they simply became us,
Speaker 1: or at least they became those of us with some
Speaker 1: portion of Neanderthal DNA and uh, and there is there
Speaker 1: is DNA evidence to support this, and then there but
Speaker 1: there's some that to take issue with leaning too heavily
Speaker 1: on this idea. Apparently, paleo anthropologist Ian Tattersall, who Shoot
Speaker 1: interviews in the Cannibalism book Um this guy, is a
Speaker 1: critic of the idea, and he argues that quote structurally, anatomically,
Speaker 1: and presumably behaviorally too, Neanderthals and modern humans were very,
Speaker 1: very different, and he says that while a certain amount
Speaker 1: of genetic exchange definitely took place, he doesn't think that
Speaker 1: they were absorbed into our population through inter breeding alone. Now, interestingly,
Speaker 1: Tattersall points out that modern humans and Neandertals managed to
Speaker 1: share the Near East for a long time, but this
Speaker 1: was before we became creatures of symbolism, as Shoot puts it, quote,
Speaker 1: an advanced symbolism driven species. These new humans at least
Speaker 1: outcompeted the Neanderthals for resources, and it's reasonable to expect
Speaker 1: that they did a bit more than that. Right when
Speaker 1: you look at at certainly the way humans have have
Speaker 1: treated other groups of humans, um, you know throughout history. Now,
Speaker 1: some researchers have argued in support of of of predation
Speaker 1: and cannibalism that that Homo sapiens uh hunted and consumed
Speaker 1: Neanderthal meat. But there's currently no clear fossil evidence that
Speaker 1: this occurred. So it might seem uh like something that
Speaker 1: they would have done. We can, we can point to
Speaker 1: aspects of human nature and and uh in humanity's historical
Speaker 1: treatment of others, but when it comes down to the
Speaker 1: hard fossil evidence of it, when it comes down to
Speaker 1: looking at bones and looking for signs of processing, uh,
Speaker 1: it's just not there. Again, we have clear evidence of
Speaker 1: cannibalism in either group of Homo sapiens eating Homo sapiens
Speaker 1: and neandertals eating the ander dolls, but uh, if it occurred,
Speaker 1: we don't have any evidence of actual intragenous cannibalism between
Speaker 1: the inder dolls and Homo sapiens. That's interesting. That being said,
Speaker 1: I think if if you were to present me with
Speaker 1: the time machine and make me place money on the
Speaker 1: on on the the chances that humans in Neanderdals, I
Speaker 1: would personally um want to place my back on humans
Speaker 1: eating neander DoLS. Well, i'd say it's probably because humans
Speaker 1: will eat anything. That's true. If something existed, humans probably aided.
Speaker 1: I bet generally a safe bet. Now, let's back up
Speaker 1: out of the human realm here, and I want to
Speaker 1: come back to something you said earlier about how a
Speaker 1: particular cannibalizing species might make sure that it's not cannibalizing
Speaker 1: its own young Oh yeah, or or members of its
Speaker 1: own near family. Because then you the closer relative within
Speaker 1: your own species is the more genes you probably share
Speaker 1: with them, which makes it more likely that some of
Speaker 1: those genes would would discourage you from eating other carriers.
Speaker 1: And so I found a recent article that deals with this.
Speaker 1: Max Plank Society article titled a Peptide against Cannibalism from
Speaker 1: April of twenty nineteen. The researchers noted that nematodes in
Speaker 1: the genus pristianchas we're all all about some cannibalism because
Speaker 1: their favorite food is worm lark. So how do you
Speaker 1: keep from consuming your own offspring? Well, the answer, they
Speaker 1: said is that they carry a quote small highly variable
Speaker 1: protein on their surfaces. So what they do is they
Speaker 1: experimented by offering adult worms of different uh of different
Speaker 1: species again within this genus. Uh, they gave them their
Speaker 1: own larva to potentially eat larva of a closely related
Speaker 1: species or larva of a related line within their own species.
Speaker 1: And in all cases they avoided their own larva but
Speaker 1: tore into everything else, so they were they were totally
Speaker 1: fine for eating another species. It's closely related to them
Speaker 1: that near cannibalism. They were also readily engaging in an
Speaker 1: absolute cannibalism. But uh, this peptide was at least aiding
Speaker 1: in their identification of their own offspring and preventing them
Speaker 1: from eating uh those uh those larva. They identified this
Speaker 1: particular gene, which they called self one, as playing a
Speaker 1: key role in distinguishing self from non self. However, it
Speaker 1: doesn't seem like it's the only factor in the decision
Speaker 1: to attack or not. And this is ultimately one of
Speaker 1: those areas where more research is going to be needed.
Speaker 1: But it does give us some idea of the kinds
Speaker 1: of of mechanisms that are in place, that kind of
Speaker 1: fail safes that are in place to keep cannibalism from
Speaker 1: just decimating a species. Yeah, and it's really interesting trying
Speaker 1: to work out exactly when and how those could controls
Speaker 1: fall into place. All Right, we need to take a
Speaker 1: quick break, but we'll be right back. Alright, we're back now.
Speaker 1: I want to talk about something related to what you
Speaker 1: were just saying, especially when it comes to praying on
Speaker 1: the larva of your own species or related species. Uh,
Speaker 1: this is a case of true cannibalism, but with interesting features.
Speaker 1: I want to talk about the cane toad or Ranilla marina.
Speaker 1: So the cane toad has an almost beaut to fully
Speaker 1: horribly ironic history in Australia. I'm sure, I'm sure all
Speaker 1: of our Australian listeners are pulling their hair out right
Speaker 1: now because if you if you read Australian writers talk
Speaker 1: about the cane toad, they there's I don't want to
Speaker 1: over generalize, but there is very often utter revulsion just
Speaker 1: the idea that they want to beat all these things
Speaker 1: to death with a sock full of quarters. Now, we
Speaker 1: we don't encourage wanton violence against wild animals, but there's
Speaker 1: a reason behind this. So in the nineteen thirties, Australia
Speaker 1: had a problem protecting sugar cane crops from populations of
Speaker 1: a pest known as the cane beetle, and in order
Speaker 1: to control beetle populations in sugarcane agriculture, they introduced a
Speaker 1: South American toad. I think this was a nive. It
Speaker 1: was the cane toad. They brought it to Australia because
Speaker 1: it was believed that this toad would eat up the
Speaker 1: beetles that were getting to their crops. And this turned
Speaker 1: out to be a horrible idea. Uh. The cane toad
Speaker 1: became a kind of breakout character, right, It's like the
Speaker 1: fawns circle, you know. It's like it took on a
Speaker 1: life of its own for the continent of Australia. It
Speaker 1: did eat some cane beetles, but it also became extremely
Speaker 1: numerous and ate all kinds of other insects, and its
Speaker 1: populations in Australia just exploded. So it's another case of
Speaker 1: an already unbalanced environmental situation due to agricultural activities and
Speaker 1: then they intentionally introduce an invasive species and things go
Speaker 1: out of whack. Very bad idea. And what's worse, the
Speaker 1: native marsupial and reptile predators of Australia, like crocodiles and
Speaker 1: like coals that might have been expected to control and
Speaker 1: exploding toad population by eating the toads were totally unprepared
Speaker 1: because the cane toad produces toxins that kill the predators
Speaker 1: that eat them, So since the cane toad was out
Speaker 1: of its native range, the predators had no resistance to
Speaker 1: these toxins and no one stinctual avoidance of the cane toads.
Speaker 1: So simply introducing these like poison candy toads into the
Speaker 1: ecosystem was devastating to some predator populations. But this threat
Speaker 1: to predators doesn't apply only to the marsupials and the
Speaker 1: reptiles like crocodiles that might eat the adult cane toads.
Speaker 1: It would also apply to perhaps smaller predators that tried
Speaker 1: to eat the cane toads also poisonous eggs. The eggs
Speaker 1: have similar poisons. So I was reading a New York
Speaker 1: Times article from two thousand eleven about research on cane toads.
Speaker 1: The articles by Natalie Angier, but the the article tells
Speaker 1: the story of a scientist named Dr Richard Shine, a
Speaker 1: biologist at the University of Sydney in Australia, who began
Speaker 1: to notice years back that cane toad eggs were being
Speaker 1: depleted by something, and at first he assumed that some
Speaker 1: predator was at risk of mass poisoning by eating these
Speaker 1: killer toad eggs uh to quote from the article. Follow up,
Speaker 1: field Stead soon revealed the identity of the caviar thieves
Speaker 1: to the researchers astonishment. Dr Shine said it was cane
Speaker 1: toads themselves, or rather their tadpoles, which would swim over
Speaker 1: to each fresh batch of vanilla eggs and quote desperately
Speaker 1: consume every slick black sphere that they could find. And
Speaker 1: then a two thousand eleven study in the journal Animal
Speaker 1: Behavior found that not only do cane toads cannibalize eggs
Speaker 1: from their own species, they strongly prefer them. When given
Speaker 1: the option to eat cane toad eggs or other food
Speaker 1: sources like similar eggs from another amphibian species, the cane
Speaker 1: toads went right for the delicious cane toad eggs. And
Speaker 1: this was just the cane toads that did this, It
Speaker 1: wasn't other uh frogs amphibian species. Now, remember that while
Speaker 1: lots of species practice cannibalism under some circumstances, no species
Speaker 1: is exclusively obligately cannibalistic like that would make no sense.
Speaker 1: But what if you're kind of edging in that direction
Speaker 1: by at least in one stage of life, preferring to
Speaker 1: eat your own kind over other forms of prey. Yeah,
Speaker 1: we're definitely in that near well, we're definitely in that
Speaker 1: that zone where it's cannibalism. But is it potentially becoming
Speaker 1: something else? Now? You would think since this is tadpoles
Speaker 1: eating eggs of the same species, you think maybe once
Speaker 1: you metamorphos into an adult cane toad, you'd get past this,
Speaker 1: uh this problem? Right? The answer is no. Studies have
Speaker 1: also shown that that like midsize adult cane toads like
Speaker 1: to eat smaller, younger cane toads. They even have like
Speaker 1: deceptive lure tactics where they will wiggle the toes of
Speaker 1: their back feet in water to attract smaller conspecifics and
Speaker 1: then just literally swallow them whole. So I've, as we've discussed,
Speaker 1: there's lots of occasional opportunistic cannibalism in the animal world.
Speaker 1: But what causes the cane toads to go so hard
Speaker 1: after their own species? Why do cane toads prey on
Speaker 1: other cane toads so aggressively, and the researchers here in
Speaker 1: this paper i mentioned hypothesize several answers with regard to
Speaker 1: the campbalization of eggs by by cane tode tadpoles. Number One,
Speaker 1: it eliminates rivals who you're probably not related to, and
Speaker 1: this has to do with the specifics of the timing
Speaker 1: of ovipositing and mating by cane toads. Obviously, it doesn't
Speaker 1: make evolutionary sense to eat your own brothers and sisters,
Speaker 1: but due to the timing of cane toade reproduction, if
Speaker 1: you're a cane toad tadpole and there are eggs in
Speaker 1: the pond with you, you can be pretty sure they
Speaker 1: belong to some other family of cane toad's. Number two,
Speaker 1: eating the eggs speeds up the maturation of tadpoles. Obviously
Speaker 1: it's free energy. And three, the resource is abundant since
Speaker 1: it's poisonous and other potential predators can't eat it, but
Speaker 1: you can, since cane toads are immune to their own poison,
Speaker 1: so they're kind of like the de facto specialized predator
Speaker 1: of their own young. It's it's like when you know
Speaker 1: somebody orders something for lunch, and there's one thing out
Speaker 1: on the buffet that you're the only person in the
Speaker 1: office that likes. So it's all for you. Enjoy this
Speaker 1: braised red cabbage robbers. And there's a quote from from
Speaker 1: Dr Shine in that Times article where he says, quote,
Speaker 1: we're talking about a tropical animal that was relocated to
Speaker 1: one of the driest places on Earth. Cannibalism is one
Speaker 1: of those clever tricks that makes it such a superb
Speaker 1: colonizer and a survival machine. Talking about the cane toad um. Now,
Speaker 1: of course this does come with some of the regular
Speaker 1: downsides of cannibalism, like it came across the two thousand
Speaker 1: eleven paper with a pretty great title. Also, Richard Chin
Speaker 1: was one of the authors on this quote. You are
Speaker 1: what you eat parasite transferring cannibalistic cane tod So you know,
Speaker 1: do cane toad's risk infection and paras parasitization by eating
Speaker 1: their own The answer is, oh yes. When a cane
Speaker 1: toad eats another cane toad and infected with, for example,
Speaker 1: nematode lung worms. This study found that the cannibal toad
Speaker 1: can end up with viable lung worms in its own body,
Speaker 1: so they are paying this cost for their cannibalism behaviors.
Speaker 1: And nevertheless, I was reading in another context that cane
Speaker 1: toads are so aggressively cannibalistic that that cane toad juice
Speaker 1: from the poison glands of an adult cane toad is
Speaker 1: one of the best imaginable baits for a trap for
Speaker 1: catching cane tone tadpoles. Okay, I think it's a cane
Speaker 1: tone cane toad tadpoles. That's a tongue twister. Uh So
Speaker 1: it smells like eggs, right, because they have these same
Speaker 1: chemicals and poisons, And it's an ingenious method for removing
Speaker 1: the tadpoles of this invasive species from a water source
Speaker 1: without harming other creatures. Like the cannibalistic tadpoles are attracted
Speaker 1: to it in swarms because of course they want to
Speaker 1: eat the eggs of their own kind, and other animals
Speaker 1: are not really attracted to it at all. So you
Speaker 1: can put traps out with this and catch thousands of
Speaker 1: cane toad tadpoles and almost nothing else. But I think
Speaker 1: it seems like this species in Australia in particular favors cannibalisms.
Speaker 1: Aggressively because it's a tough physical environment, like they need
Speaker 1: to reproduce in water, and yet it's a relatively dry landscape.
Speaker 1: And yet at the same time, there's an abundance of
Speaker 1: their own species due to a lack of adapted predators. Interesting,
Speaker 1: So I feel like one of the crazy things about
Speaker 1: this is that a lot of what they're observing here
Speaker 1: it's it's it's nothing you would observe, at least on
Speaker 1: this scale in their natural habitat, Like they're the cane
Speaker 1: todes of Australia have this kind of bloated and and
Speaker 1: an natural space in the ecosystem that has yet to
Speaker 1: be uh, you know, sort of recalibrated by other factors. Yeah.
Speaker 1: Now I don't know what they're what they're cannibalistic tendencies
Speaker 1: are like within their native range, it might be something equivalent,
Speaker 1: but but this seemed to be focused on the ones
Speaker 1: that are in Australia, So I'm not sure how prevalent
Speaker 1: this would be in the species as they live in
Speaker 1: South America. It's like, if you know, if cannibals took
Speaker 1: over a date care, like and you observed it on
Speaker 1: like the first day of activities, you know, it's like
Speaker 1: everything is going to be crazy that first day. Hopefully
Speaker 1: by day three or four things would have have settled
Speaker 1: down and or the police had shown up, etcetera. Uh.
Speaker 1: And of course before that, before the cannibals took over
Speaker 1: the daycare, you would not have this um, this out
Speaker 1: of balance scenario in which to observe how things would
Speaker 1: take place. That's a beautiful analogy. Wrout. Before we wrap up,
Speaker 1: I wanted to mention just one more type of predation
Speaker 1: that we might consider a kind of close analogy to cannibalism,
Speaker 1: and that is when you kill and eat an animal
Speaker 1: that is not the same species as you, So it's
Speaker 1: not cannibalism, but which makes a living the same way
Speaker 1: you do, maybe does the same job as you. And
Speaker 1: this brings us to a biological concept and as intra
Speaker 1: guild predation, in the words of entomologists j Rosenheim and
Speaker 1: Jason Harmon into intra guild predation occurs quote when two
Speaker 1: consumers that share a resource and which therefore are potential competitors,
Speaker 1: also engage in predator prey interactions with each other. So
Speaker 1: you've got two different species competing for the same resource.
Speaker 1: Like how at different times. Maybe Elmer Fudd and Yosemite
Speaker 1: Sam are both trying to go hunting for bugs Bunny.
Speaker 1: But what if instead Elmer Fudd kills and eats Yosemite Sam. See,
Speaker 1: this solves two survival problems at the same time. It
Speaker 1: provides an immediate meal. You get to eat Yosemite Sam,
Speaker 1: and there's energy in that. But it also reduces future
Speaker 1: competition for the webbit. Right, all right, it's a it's
Speaker 1: a basic Freddy versus Jason scenario. Right, Yeah, that's pretty good.
Speaker 1: So the benefits of this kind of thing are obvious,
Speaker 1: and there are a couple of versions here. There is
Speaker 1: asymmetrical inter guild predation, and this occurs when two species
Speaker 1: compete for the same prey resources and one of those
Speaker 1: two species also kills and eats the other. And then
Speaker 1: there's what you might guess, the other half of that,
Speaker 1: the other side of that coin, symmetrical intriguild predation. It's
Speaker 1: when two species are in competition and they also both
Speaker 1: kill and eat one another. If one predator is regularly
Speaker 1: bigger than the other or something. This kind of two
Speaker 1: way mutual predation can often cross the lines of life phases,
Speaker 1: where say one predator adults of one predator prey on
Speaker 1: the juveniles of the other predator. Okay, So with asymmetrical
Speaker 1: um intriguild predation, there's always going to be probably a
Speaker 1: clear winner, yeah, Like the the larger of the two
Speaker 1: competing species is going to be the one that eats
Speaker 1: the smaller. But in symmetrical interguild predation, it could go
Speaker 1: either way depending on body size, phase of life, or
Speaker 1: other factors of superiority exactly. And so this type of
Speaker 1: stuff often happens in insects and arthropods that share the
Speaker 1: same prey, like in some centipedes, but it also occurs
Speaker 1: in large mammalian carnivores like canids and fields. They often
Speaker 1: prey on one another when they're competing for the same
Speaker 1: food resources, for example lions and wolves, or coyotes and
Speaker 1: foxes or bobcats. According to a n paper in the
Speaker 1: American Naturalists by by Palomari's and Caro uh quote, interspecific
Speaker 1: killing among mammalian carnivores is common in nature and accounts
Speaker 1: for up to sixty eight percent of known mortalities in
Speaker 1: some species. So there's some carnivorous predatory mammals for which
Speaker 1: more than two thirds of their deaths are caused by
Speaker 1: other predatory mammals. And because inter guild predation accomplishes two
Speaker 1: different goals at the same time, inter guild predation can
Speaker 1: be extremely useful as the survival adaptation. It's a very
Speaker 1: efficient way to do things. Of course, since members of
Speaker 1: the same species are often in competition for the same resources,
Speaker 1: the same advantages that apply to inter guild predation often
Speaker 1: apply to straight up cannibalism. Right because you know you,
Speaker 1: you and the other one of your species you're you're
Speaker 1: probably also in competition. But straight up cannibalism is more
Speaker 1: likely to come with the other downs sides, such as
Speaker 1: reducing the gene pool of your own species, making making
Speaker 1: more difficult, exposing you to more parasites and diseases, and
Speaker 1: so forth. Now you said you were going to bring
Speaker 1: all this back to social media. No that I was.
Speaker 1: I was thinking about this and I started to think
Speaker 1: that I see parallels between the strategy of intra guild
Speaker 1: predation and some types of business strategies, especially like in
Speaker 1: digital media where we work. So why don't you think
Speaker 1: about this example? What did Facebook due to the rest
Speaker 1: of the web? Like digital media companies are in competition
Speaker 1: for audience. You can almost think about audience as their
Speaker 1: prey in a way. They make money when more people
Speaker 1: spend more time on their side or their platform. Facebook
Speaker 1: was a digital media company in competition for users attention
Speaker 1: and time, and their competitors were the other places where
Speaker 1: people might spend their time on digital devices, other websites,
Speaker 1: other apps, other platforms. So it seems to me Facebook said,
Speaker 1: you know, instead of just competing with these other media platforms,
Speaker 1: I will eat them. And that's sort of what it did.
Speaker 1: Right So now instead of just going to your blog
Speaker 1: or homepage or whatever, people would go to your Facebook
Speaker 1: page or just follow you on Facebook or rely on
Speaker 1: Facebook to keep people updated on what you're doing, whether
Speaker 1: you're a person or a business or a content provider.
Speaker 1: And I think the analogy holds that Facebook functions like
Speaker 1: an asymmetrical intriguild predator. Here it gets double benefits both
Speaker 1: by getting a direct meal off of you, like it
Speaker 1: gets the traffic that you would be getting elsewhere that
Speaker 1: gets just subsumed into its diet of traffic, and it
Speaker 1: reduces competition in the future by training people evermore to
Speaker 1: just go directly to Facebook instead of to other sites.
Speaker 1: And apps, And it makes me wonder if there are
Speaker 1: other examples in the business world where there is something
Speaker 1: like intriguild predation going on, where where one business gets
Speaker 1: double benefits out of assuming or subsuming another one. Yeah,
Speaker 1: I think you may have something. You may have a
Speaker 1: point there. I mean, also, it's very easy to imagine
Speaker 1: any of these large media companies as kind of a
Speaker 1: bloated cannibal king feasting and blood soaked on a on
Speaker 1: a pyramid of bones of its competitors. Uh, and the
Speaker 1: attentions of its clients. I couldn't put it any better
Speaker 1: than that, Robert, But but I feel like we're kind
Speaker 1: of given normal predators, a normal cannibals a bad name
Speaker 1: by associating them with with that kind of ghastly you know,
Speaker 1: very uh, you know, human centric image. That's true. Normal animals,
Speaker 1: even the ones that sometimes practice cannibalism, are not. Corporations
Speaker 1: don't decide that hippos are bad now just because occasionally
Speaker 1: hippos will eat another hippo, They're still they're hippos. They're animals,
Speaker 1: they're they're living within an ecology, and they're doing what
Speaker 1: they have to do to survive. Yeah, I mean, it's
Speaker 1: like with mice and hamsters and so forth. You know,
Speaker 1: it's like you can if you get one as a
Speaker 1: pet and you in your you end up tricking yourself
Speaker 1: or falling into this idea of thinking them it's like
Speaker 1: tiny furry people and you're a little furry friend that
Speaker 1: lives in this box and scurries around. And then but
Speaker 1: then if you're going to become horrified when they engage
Speaker 1: in something in humans such as cannibalizing their young, uh,
Speaker 1: And that's I mean, you should take that as a
Speaker 1: learning lesson. You know that this is ah, these are
Speaker 1: the perils of of anthropomorphizing, uh, the animal world and
Speaker 1: then then the wild world and the natural order of things.
Speaker 1: But really, cannibalism is simply ubiquitous and it is going
Speaker 1: to be practiced by um, you know, most of these
Speaker 1: organisms at one point or another. Totally exactly right. Though
Speaker 1: I want to make clear also I'm not implying that
Speaker 1: the inverse excuse supplies where you can you can take
Speaker 1: that logic and apply it back to human institutions like
Speaker 1: people and like corporations and all that, because come on,
Speaker 1: they got people in them. People out oft know better.
Speaker 1: And also we are not condoning human cannibalism, right, that's
Speaker 1: what I mean. Yeah, I think you're just talking about
Speaker 1: the digital media, but neither one neither actually eat killing
Speaker 1: and eating other humans, nor doing stuff that's akin to
Speaker 1: cannibalism in metaphorical way right now, Survival cannibalism, that's that's
Speaker 1: a different scenario. If somebody's already dead and you've got
Speaker 1: nothing else to live on. Maybe maybe, But then again,
Speaker 1: like that's that's a decision you're going to have to
Speaker 1: make in those dire situations. We can't make it for you.
Speaker 1: It would be you know, it would just be rude
Speaker 1: of me to rule on that. I do not know
Speaker 1: the particulars of your survival cannibalism. So if you are
Speaker 1: in a survival cannibalism situation right now while listening to
Speaker 1: this podcast, I cast no judgment. Eat your earbuds. If
Speaker 1: that that's what you should do, well, maybe if you
Speaker 1: chew on the earbuds a little, it can distract you. Right,
Speaker 1: It's kind of like sucking on a button if you're thirsty, right,
Speaker 1: the I don't know if that actually works, but that's
Speaker 1: the old wives tale, right. This has been a lot
Speaker 1: of fun, Robert, Yeah, another page in the book of Cannibalism. Uh. Likewise,
Speaker 1: with a lot of these topics, there's so much more
Speaker 1: we could discuss, and cannibalism will probably come back around
Speaker 1: to cannibalism again, either generally or you know, regarding a
Speaker 1: specific organism at some point in the future. Uh. Also,
Speaker 1: I want to stress again that Bill shoot book Cannibalism
Speaker 1: is excellent. Do pick it up. You wrote another one
Speaker 1: on vampires dealing with vampiric organisms, and that too is
Speaker 1: an excellent read. So either of those books are wonderful
Speaker 1: if you want to, like I guess you know, slightly
Speaker 1: uh slightly ghastly um biological read, They're they're great books.
Speaker 1: In the meantime, if you want to check out more
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Speaker 1: that's the other show that Joe and I do. It
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