Daniel and Kelly’s Extraordinary UniverseHow Many Babies Should You Have? (featuring Katie Goldin)
Daniel and Kelly chat with Creature Feature's Katie Goldin about babies and how much to care for them.
Daniel, did you want to ask an alien related question? Or are you good?
Oh my gosh. The answer to that is always yes.
Green is the answer green?
Yeah, Katie. My question is what color are alien nipples?
M you know what, I've always imagined them as lavender. Isn't that funny?
Maybe they also taste like lavender?
You hey, you know what.
We're getting into some real strange territory here, right.
That's a little taste of the conversation we have on today's episode. It's not about aliens, mostly though it is a little bit, And it's not about nipples mostly again, though it is a little bit. It's about babies. How many babies should you have? Some critters have lots of babies and hope a few survive. Others have just a few babies and take extra special care of them. What's the best strategy evolutionarily? Why do some critics choose one or the other? Does biology make any sense at all? Or does it just depend We'll dig into that on today's episode of Daniel and Kelly's Extraordinary Reproductive Universe.
So on today's show, we're talking about the birds and the bees. So decide ahead of time if you think that's an appropriate topic for your children. Thanks for listening.
Hi. I'm Daniel. I'm a particle physicist, and I have two kids so that neither of them have to be the middle child.
Yeah. Hi, I'm Kelly wider Smith. I am a parasitologist. I have two kids because that's all I could handle.
I'm Katie Golden. I host a podcast called Creature Feature. I have a dog so that she doesn't have to be a middle child.
Katie, it's so great to have you on the show.
Yeah, I'm so excited to be here.
I too love parasites, by the way, so we've got that in common.
I mean, that's the most important thing to have in common, I think.
Yeah, that was what got me so into biology. Is a class I took. The official title of the class was like about mimicry, but the professor who ran the class was like so interested in parasites.
That was basically all we talked about.
And it's like he made the right call because that was super interesting, and it's like I love hearing about all these weird little freaks, and I gotta know more.
What if it was a parasite that affected the host and made them interested in studying parasites.
I'm probably chock full of that.
Carl Zimmer's book Parasite Rex like changed my life. Yeah, it was going to be a parasitologist after reading.
That, seeing the little isopod that's the parasite for fish, just like peeking out from a fishmouth, going like, hey U that altered my brain chemistry forever.
It's pretty awesome. So I was talking to my friend Stacy Farina the other day and so the story with that isopod goes that it like eats the fish's tongue and replaces the tongue, and she studies fish like skeletal stuff, and she was like, you know, I've looked at a bunch of them and the tongue is still there. Guys, Yeah, what So I think they're actually just like clinging to the tongue and they're eating stuff, but they haven't really eaten the tongue, which I think is part of like what the pop side.
Well, it's yeah, it's like the idea that they're now acting as the tongue. I thought they fed off of the blood supply, so they may cause some atrophying of the tongue, but it's not so much that they eat the whole tongue and then replace it. It's that they're stealing nutrients from the fish, and then when they leave the fish, usually the fish doesn't survive because it's basically mangled its tongue to the point where it can't use it as much anymore. That's my understanding. But also I think we have a fairly poor understanding of them because it's not every day that you find these little guy because you'd have to just like open up a bunch of fish mouths of like, let me see inside your mouth what you got in there?
You know all the best stories, Katie, I look in a lot of fish mouths.
And that's why we invited Katie on the podcast today to talk to us about babies.
Yes, which hard to segue from fish mouths to babies.
It's really hard to keep you guys on track. But I'm doing my best here.
Well, I mean, what if we get the chance to talk about parasites, we will, But pulling back. So the reason we're talking about babies today is because we had a question from a listener, Nathan Ryan. He wanted to know about the benefits of having lots of babies relative to the benefits of just having a few, and so he was like, why would you ever have just a few when you could just flood the environment with babies? And ecological theory has a lot of ideas about that, and so I thought today we would talk about how many babies should you have?
Thank you, Kelly for taking us back on on track and away from parasites, as difficult as that is for you. I love this question because in his email he specifically mentions the two kinds of strategies are strategy and case strategy, which describe having lots or few babies. That's really cool because I'm excited whenever I see a theory in biology. What it's not just descriptive like naming the parts of the flower, but building a mathematical model to understand the dynamics and how it all works. See, even underneath biology there has to be math. So we're going to dig into this question by walking through a bunch of examples of extremes lots of babies, few babies, and then thinking about whether the current theory about our in case strategists is actually working or not.
This is such a good question in both personal lives and in olationary biology.
Do you think Nathan is considering whether to have like two or like fifty kids.
You better be considering whether he wants two or fifty wives. If he's going to have that many kids. That's a complicated question.
Well he could be you never know, right.
Right, Yeah, No, that's a good point.
What do you think is the maximum number of kids any individual human has ever had?
Mm?
Genghis Khan.
You know, I wouldn't be surprised if some of those warlords just like did get around enough to have like one hundred kids, not by one person.
That would be not possible, right, We all have limits, you know.
I think a lot of that though, is probably them thinking they have one hundred kids, or it's like those are my kids too? And got news for you, buddy, Probably not.
You don't always know. That's one of the benefits of being the woman.
You can be sure usually in most circumstances.
Yes, I remember reading that there was a woman in the seventeen hundreds who gave birth to sixty nine children.
How would that even work?
Because it's sixteen pairs of twins, seven sets of triplets, and four sets of.
Quadruplets and she lived through all of it.
Yeah, And sixty seven of the sixty nine survived. But this is from the seventeen hundreds, and it's sort of like story and not like, yeah, well documented.
Yeah, that would be intense.
I have a hard time believing that, maybe just because I simply don't want to believe it like that.
It boggles the mind, it does. Yeah, yeah, I don't think I want to believe it either. But let's jump into the main episode then. So we thought that first, if you're thinking about how many babies you should have, then you should think about how much energy it's going to take for each one of those babies from you. So how much energy is it going to take to protect and provision the young? And actually, we're not really talking about humans at all today. We're talking about non human animals. And so let's take a little walk through who does the care in different animals And so I'll start with fish. Actually, and fish, the males do a lot of the care. And you know, this is possible because most of the time eggs are put out into the environment and fertilization happens externally, and so you know, either one of them could be the one who splits. But for whatever reason, it's been the males who tend to so, for example small mouth bass and large mouth bass. The males will sort of use their fins to clear out an area, like a little depression where a nest will be, and then a female comes by, and if she decides the male sexy enough, she'll deposit some eggs, and then the male will deposit his sperm, and then it's his job to stay there and use his fins to aerate the eggs and make sure there's fresh water passing over them that through diffusion can like get into the eggs to keep those guys alive, and then also make sure that no predators eat those eggs, because they're amazing little balls of energy that would be great for like little minnows or crayfish. And so he's got to like defend the nest.
Tasty little omelet of babies right there.
That's right, that's right, pre made, and so I think it's pretty energetically expensive. They don't tend to eat, well, this is happening, and it's sort of not clear why, but maybe it's because they can't control themselves and they might eat the eggs. So anyway, they tend to not eat. It's a lot of work, but the males are doing most of the care, and so the eggs hatch, they swim up, and when they swim away, the male's job for the most part is done. He stays with them for a little while, but then they go off on their own. That's quite different than what happens with birds, right Katie.
Yeah, I mean birds have a lot of different strategies. You have a lot of bird species where it's the female taking care of the offspring because she lays the eggs, and she of course has to keep the eggs warm under her body, so she stays with the nest. But you also have a lot of species of birds who work together, so you have a pair of parents, particularly in harsher environments, so sea birds in particular penguins obviously in their very harsh Antarctic environments. There are other species of penguins that live in warmer environments, but an amazing example is great hornbills. So they are a species of bird that go to extreme lengths to protect their eggs. The males actually will seal the females into a hollow inside a tree using his own feces, in her feces in a bit of mud to create sort of a plaster beautiful oh biology. Yeah, and then they leave a tiny hole and the male will go out and very devotedly bring back food for the female and then for the chicks once they hatch. And the reason that there's so much care in these situations of both parents working together is environmental stressors. So for the hornbills, it's in the places that they live in Southeast Asia. In these forests, there's a ton of predatory snakes who eat eggs, eat chicks, so so many arboreal snakes that creating sort of a sealed off, you know, bunker for the female and the eggs is really important. For seabirds, the there's a lot of kleptive parasites. Those are other birds that want to steal resources, including eggs, including eating chicks. It's just a very very harsh environment, particularly the ones that live in cold environments. So and also finding food is difficult. They have to leave the colony, go out to sea, go fishing, and so both parents need to kind of like switch off and alternate in terms of like taking care of.
The egg, taking care of the chicks. If they didn't.
Both put all of their effort into it, most likely their chicks wouldn't survive. And also just an interesting note. In species of birds where they're both working together as a pair, usually there's not as much sexual dimorphism, meaning like both of the male and the female look very similar. Also, when they're mating, both of them will often do some kind of mating display and try to impress the other mate equally because they're both putting in so much effort into the offspring, they're both equally trying to assess whether their mate is going to be good wears. In a lot of other species, where the female is the one doing most of the child rearing, it's the male that's trying to impress her because she's the one putting all of this investment into the offspring, Whereas the male is just kind of like going around sewing as wild out, so for him, he doesn't need to be as cheesy, where as the female needs to be really cheesy.
So in this scenario where the female gets sealed in with the eggs and cares for them, do you think she's like into that or is she like tracked in like a slave in his like weird poo palace that he builds for her.
She's into it.
She can actually kind of kool aid man break out anytime she wants, but she's in there, and as long as the male comes and like feeds her, she will stay there with the eggs take care of them. If the male stops feeding her, I think she will break out and leave the eggs. And so there's a mutually bit official investment there, like the male coming back to feed her. Usually the male would only not come back if he came to some devastating ends. So the female completely cooperates and that she actually helps build the wall as well. So it's not like not a casko of a mantiato, but with porn bills.
How would you have felt, Kelly, if you've been sealed into a room with your babies by your husband's poop.
I mean, our house is pretty messy when we first had our kids. I don't know how different that was, and the diapers were piling up. I guess it wasn't zac species, It's right. I think I would have left, even with young people in the houses.
But he's getting you uber eats like all the time, so that's an important aspect of it.
But so the big picture here is that we're seeing lots of different kinds of scenarios, different strategies in different scenarios, and so the idea is that they're responding to the different situations they're in by developing these different strategies.
That's right.
Also when you have major differences among different types of animals, so like, for instance, mammals, usually it's the female doing most of the caring for young and a big reason for that is lactation. So like mammals, mammary glands, mammals have this ability to lactate and feed their offspring and this is how they care for very young babies and so usually not always, this means that the female is the one doing the primary caregiving for the offspring. You do see this, of course in other types of animals, so like there's a type of limbless worm like amphibian called the sicilian, which actually has something akin to malk Some species have this like viscous fluid that it produces from its kloeca that the offspring feed from. Like some species they actually allow their offspring to sort of chew on some like thick nutritional skin that they have a little excess mom jerky. And in these situations, the mom actually offers parental care to the offspring. But also in mammals, another exception is that there's a lot of very social species of animals where there's both male and female parenting. I mean humans is an example. There's also alloparenting, which is when either loosely related or non related individuals take care of the offspring that is not directly theirs. That's like common in a lot of different mammalian species, and that culminates into a version of mammals that actually becomes somewhat more insect like like naked mole rats who have a use social system where they have a queen who reproduces, and everyone else is basically facilitating the queen's reproduction. So that's like an extreme example of mammals going more towards like a b ant colony type model.
I've heard this story. I think it may be apocryphal, and I want to ask you that in humans, it's possible, though difficult, for males to lactate given the right circumstances. Is that true or not?
It's true.
It's basically like hormones will determine lactation, So if some men naturally will produce, some hormones that may actually cause them to do a little bit of lactation. And actually, if someone takes hormones, you can induce lactation, and so you know, yeah, I mean honestly, like the differences between say, like male and female phenotypes in humans is so guided by hormones that when those are either you know, you have atypical levels of them, or you introduce synthetic hormones, so you can completely alter the phenotypic representation that includes functions like lactation.
Does that mean that males have mammary glands they're just.
Not active, yes, yes, essentially, yeah, mind blown.
Yeah, you've got nipples.
You've got I was aware of the nipples. Thank you.
Just making sure.
Let's give Daniel a tour here.
Of these things.
Just call them my chest buttons. Yeah, the memory glands and then are very underdeveloped. But there are like cases with like genetic differences where some men will have larger breasts and larger memory glands and some men can lactate, and yeah, that can totally happen, but you know it's not necessarily going to be enough maybe to feed a baby. But hey, you know what, get whatever help you can is what I say, every drop probably counts.
No, try, gentlemen out there. She's not the only one who has to wake up in the middle of the night to feed the baby.
Yes, that's right. Humping is a great technology. Yes, so when birds they make that like crop milk, do the males do that? Tours, that's something that just the females do.
Males can also make crop milk. I think it depends on the species, but yes, you do have a mutual ability a lot of species to make crop milk that is not necessarily tied to you know, just the females, but some animals do, like the sicilian that I mentioned, like that can be just the female. And probably the explanation for that is in a lot of species, basically, unless you're an asexually producing animal, it's the female who's going to be giving birth to the offspring. Or unless you are a sea horse, in which case there's like basically two birds right where the female lays the eggs and does develop inside the males and then he gives birth to the live offspring. So the reason that you will often have cases where once an animal develops sort of a tool for offering nutritional aid to their offspring that it will be female is because usually it's the female who gives birth to the offspring.
Now, insects are heroes of mine because they don't do a lot of parental care. Now, Katy, can you tell us about those?
So later we're going to talk a little bit about R and K selection and just very briefly, our selection being you have a ton of offspring, you know, a bunch of cheaply made offspring, and K selection being you have maybe one or two really high quality offspring. It's very much an over generalization, but we'll get into the details later, but insects are sort of like the absolute champions of our selection, popping out enormous numbers of babies and just highly expendable babies.
Either love them or you have lots of them, right, these are the two options.
Well, essentially, it's a little more complicated than that, but yes, that is like sort of the basic idea behind it, and parental care is really rare in both insects and arthropods. So there are some notable exceptions such as like, usually it's the female again for the reason that I said, which is the female that lays eggs or gives birth to offspring, so scorpions will carry their young on their back. Centipedes will kind of curl up in this cute little nest like cradle for her offspring, which it's very adorable. There are even types of spiders like the desert spider who basically once she lays her eggs, she starts to digest her own insides and then will regurgitate her own juices for her offspring to feed on. And she does not survive this process. She turns herself into like a mom smoothie and then.
Allows her offspring to eat her.
It's called matrophagi eating one's mother, and the babies will eat like ninety five percent of her biomouse.
You know, it's not cool. There's no petrophage or why are there no dad's getting.
Eat there's probably some dads getting eaten, but yeah. The reason that it's usually matrophagi is because of the fact that usually it's the mother that gives birth or lays the eggs.
But there are some very rare.
Examples of both the mother and the father and insects taking care of their offspring. The only example I can think of there may be more, but this one is also really cool is burying beetles. So these are beetles that will find the carcass of some small animal and then we'll bury it. And the reason they do this is so that they can lay their eggs on a source of food, so they bury it to keep it away from other competitors, and then they lay their offspring in this sort of like little den of rotting meat. And then they actually will stay. Both the mother and the father bearing beetle will stay and protect their offspring, so they'll maintain the larder, make sure they have plenty to eat, and then they'll fight off competition and predators until the larva pupate into their more adult forms.
So that's super rare.
It just doesn't happen very frequently in insects or in arthropods because their usual techniques just have a huge amount of offspring, and statistically a lot of them are gonna make it.
So I think any of the moms or dads out there are probably feeling a little bit better about what we went through when our kids were young right now after hearing about the insect examples. But let's go ahead and take a break, and when we get back we'll talk a bit more. About the costs associated with having babies, and we're back. So we've gone through and we've talked about the different in ways that the responsibility of taking care of the kids tends to be divided up in the animal kingdom. So now we're going to dig into some examples of it being costly to have offspring. And I think for most of us who have had kids were like, yes, of course it's costly to have offspring. Like a bunch of us moms lost weight while we were breastfeeding because it's calorically expensive and you're not sleeping, and you know it's obviously costly. But that's true for animals, not just humans. And there are some really nice examples of this. So, for example, David Lack did this long term study of these birds called great tits Paris major and confession, I didn't realize this was a bird species the first time I heard about these and a person who ended up being my PhD advisor started talking to me about great tits and I just had a like deer in the headlights moment, and it took me a second. He said something about eggs and I was like, ah, I think we're talking about birds or fish. And eventually.
The first time I heard about great tits was when I was on a bird watching expedition with the bunch of senior citizens when I was in high school, and this sweet little old lady leaned over to me and says, now you have younger ears, so see if you can hear some great tits.
That doesn't make any sense to.
Place sound life, Yeah.
Yeah, keep your eyes peeled for great tits. Just coming from this octagenarian. It was a wonderful moment.
She's probably seen a lot, she knows right, it's.
Nothing you ain't seen before.
Maybe we should put a little warning at the top of this episode.
But more broadly, like, we're hearing these examples about like different strategies, males taking care of the babies, females taking care of the babies. What do we learn sort of broadly from these examples, Like are there obvious trends here where people respond in certain ways to certain circumstances or is it just like a scattering of examples And the answer is it all depends.
There are patterns, for sure. There have been attempts to kind of put the patterns into much more simple mathematical equations, which sometimes work but then sometimes they fail. But in general there are patterns. But because there are so many essentially factors that are a component in these evolutionary quote unquote choices, it can be difficult to see the pattern from the noise, but they do exist, and there have been some like observable patterns that have been found that can kind of help sway the decision in terms of like what type of offspring strategy species end up falling into, right, Kelly.
Yeah, so we are essentially making the argument that it depends today, which Daniel will not be surprised to hear. So I found this quote from a textbook that I used in grad school, and it's the evolution of care behavior is complex, and we are still far from fully understanding which factors really influence the evolution of care in both males and females. Models are arguments like the ones presented above in this textbook may also prove too simple because they generally consider just a few factors at a time. So we're talking today some of the different solutions that evolution has landed on and some of the different factors that influence the decisions that end up getting made over evolutionary time. But it really does depend Life.
Is messy and lots of factors must come into play, predation and environment and variability and all sorts of crazy stuff. It'd be amazing if you could boil it down to just a few variables like you can in physics. I don't know why physics ever works, frankly.
So yeah, we're going to talk about a lot of variability, and then we're going to narrow down a little bit on one attempt to sort of summarize what we see and why we see it. And then we're going to talk about how that sort of way of summarizing things fell apart, and how now we're back to trying to find more complicated models that include more variable.
All right, now I'm ready to talk about great tits.
That's great.
It's always good to get into the math before we start talking about great that's right.
That's right. That's how most of these conversations work out. So there's this researcher in England. Great tits are these tiny little birds, and there's this population that's been monitored for decades and all of the birds, or as many as possible, are caught every year they're banded. And then you look to see who's coming back year after year. These birds tend to lay one set at one clutch of eggs once a year, and the army of graduate students who were working on this for decades would go out and they would count how many eggs. They would weigh the birds soon after they hatched, and then they'd measure survival by determining who came back. And they were looking at a large enough area that I think they decided that, you know, the birds who flew to join a different population. That was a negligible number of birds, so they pretty much were keeping track of everybody. And they noticed that these birds usually lay eight or nine eggs, and that the more eggs there were in a nest, the smaller the offspring would be. And you could test this by moving eggs between nests and looking to see if you like, make the parents feed more offspring, What does that do to the size of the birds and the parents are out from like dusk to dawn, gone to dusk, that would be it from done to dusk.
Trying depending on how you look at it.
Yeah, they depends whether drinking, yeah.
Right, drinking caterpillar juice or something yummy. And they found that the more birds they had to feed, the smaller the birds were, and then if you look at those small birds, they're less likely to survive and show up again in the population as adults. So if you have too many babies, those babies don't seem to make it, and you've expended all of that energy for nothing. But they did some like mathematical modeling and moving some eggs around, and they ended up deciding like, okay, but it looks like the birds are producing fewer eggs than we think that they could be producing optimally every year that they could feed enough and enough of them could come back in the future. Why aren't they making more eggs? And the idea here was that you're not just trying to maximize the number of eggs that you're producing in one year. You're thinking about your lifetime reproductive success. So if you go all out and you raise as many eggs this year as you can, probably gonna exhaust yourself and not be able to survive until the next year so that you can have more offspring. And to be honest, because ecology is complicated, as far as I know, they didn't find good evidence for that in this system, but they have found evidence for that in other systems, so like in European kestrels, so these are birds that are predators and they pick off little mammals. They found that if you put extra eggs in a nest and like those adults had to feed more babies, the babies were less likely to survive to adults, and the adults who had more babies in their nest were less likely to show up the next year, so they were less likely to survive the winter.
It just sounds though, like they instead of like showing up. I know what you mean is their survival rates, but it does kind of sound like when you gave them too many kids.
They're like, that's it. I'm out, I'm leaving done.
That's right, I'm gonna go become a dancer. I'm done. But you know this is ecology, right, So the answer has to be it depends. And even though you feel like you have a nice model, nice theory for understanding how this stuff works, if you look in a different system, you don't always find support. So David Resnick studies guppies. These are these tiny little fish that you find in Trinidad, and he took them into I think this was a lab study, and he compared the females who were paired with a male and could mate to females who didn't have a male. And the idea was supposed to be that the females who had to produce young would end up weighing less because it's energetically expensive than the females who didn't have to produce young. But they didn't find that the females who had to produce babies just ate more. That's what I did for sure, and so they ended up being in just as good shape. And so you know, this kind of stuff can depend on like how many resources are available in the environment. Like if you're feeding baby chicks, but it's a year where there's just loads of insects, maybe it's one of those years where the cicadas come out of the ground and there's just food everywhere, then you know you don't have as many trade offs.
So if you can just sit on the couch and eat Ben and Jerry's, then you should have lots of kids.
And so they quote from earlier is about how there's lots of other factors to consider.
Flavors of Ben and Jerry's are available. This kind of stuff.
People often ask like can I feed, say, wild birds, and the answers It depends again because one of the problems if you feed wild birds too much, you actually give them a false sense of security in terms of like, oh, there's a lot of plenty, I can have a lot of babies, and then they end up having more babies earlier, and then they might miss key points in terms of like some species maybe time their offspring to the emergence of certain insects, right, like they follow the breeding cycle of caterpillars or other insects, and then they may if you give them too many resources artificially, they may actually have more offspring earlier, and then when they migrate, right, they don't stay in your backyard forever. Then they migrate, and then they don't actually have the resources that they kind of were led to believe they would have. It can actually cause a population crash. So like there's a lot of like weird unexpected consequences is where a lot of species have this kind of like timing system, and they can also kind of they can change their breeding behavior based on the stress and the resources that they have available to them.
What if you feed wild birds, but you do it consistently. You don't just like yanke it away from them.
Well, it depends, like if they migrate, then you'd have to follow them. It's like, all right, where are you going?
Get on a plane?
You tag them and migrate with them.
And if you're just feeding birds consistently and they stay in your backyard, that's how we got chickens.
That's not so bad, that's delicious.
You can also transmit diseases at feeders, Yeah, that's true. It had been like fifteen minutes since we had talked about parasites, so I had to pull that back.
When you have a really crowded public feeder, you've got a lot of birds, you know, rubbing up against each other, so then they can transfer diseases. So like, especially when there's like avian flu going around, it's probably not a good time to take in those feeders.
We had a bird feeder our backyard and there was a blue jay in the neighborhood and who really liked like the bigger seeds. I think it was the some flower seeds. He was also a bully, so he would like chase away all the other birds and then he would sift through and just like throwing seeds left and right to get to the some flower seeds and gobble them up, but making a mess everywhere, and all the other birds were scared. We had to like try to chase this guy away.
Yeah, we have a family member like that. We stopped inviting them to say. So, we've talked about a variety of different ways that nature has sort of solved the problem of who takes care of the offspring? How many offspring do you have? But sometimes it's complicated, So let's move on to this idea of R and K strategists. So this idea was meant to sort of come up with a theory that would explain why sometimes you get organisms species that make loads of offspring and then other times you get species that just make a few offspring. So what kind of conditions would promote doing something crazy like having thousands of offspring? So the idea here is that maybe you have some environments that are just changing all the time. They're unpredictable. Maybe like periodically fires come through and they just sort of devastate the environment. And so it's not necessarily that like resources are limited. It's just every once in a while something catastrophic happens and in that case, as the theory went, the idea is that you should produce loads of offspring, and you should start producing these offspring as young as you can, so that you can get as many chances at making offspring as possible, and that you can fill any new niche that opens up by having all of these new offspring. Whereas, if you're in an environment where there's a set number of resources, that environment is pretty stable, it's pretty predictable, then you should invest in making a few number of offspring that are in really great shape and they're really good competitors because there's going to be a lot of competition for those resources since everybody's sort of at the limits of what the environment can handle in terms of the amount of resources that are available there for everybody.
Does that make sense to you? I mean, I try to imagine myself as a parent in this circumstance, and like it seems like that makes sense under the assumption that you can do nothing to help your kids survive, Right, you should just have lots of them because it's all random. But I'm imagining, like if I have kids in suburban southern California where things are pretty stable, versus I have kids in like post apocalyptic Mad Max scenario, Like, am I going to pump out one hundred kids and then just like let them run crazy free and hope they survive? It feels to me like I'd still be better off having few kids and trying to like navigate them through the chaos.
Well, evolution has selected our species over time to be really good at making a small number of offspring, and you can use our intelligence to sort of help them survive in this complicated environment. I would say that we don't necessarily have the ability at this point to make as many offspring as it would take. To think of yourself as an R strategist, what's your take on this, Katie.
Yeah, I mean I think it's kind of comes down to probably very complicated statistical probabilities that I have no way of kind of conceptualizing. But you know, it's sort of like a I'm going to make a stock market comparison, but I want to make it clear I don't know anything about investment. But if you have like a really risky market, right, like you diversify your portfolio in general, right, Whereas maybe if you have it more stable market, It's like, man, I know that everybody loves apple juice, so I'll keep investing in apple juice. I don't mess around with the stock market because I truly don't understand it.
I don't think apple juice is a growth industry. Katie's not an investment. Don't take advice from Katie, folks.
If I drink enough, it's a growth industry for me. But like, one thing is that you can think of it in terms of like an individual's success, right, Like I'm a parent, I can like make sure my child reaches adulthood. But you can also look at it in terms of just like the spread of a bunch of genes.
And there have been.
Some sort of like back and forth arguments about like what matters more genes or phenotype, right, but in general, like sometimes you may have a situation in which having a ton of offspring and not taking care of them but just leaving it up to chance is the best strategy, even if, like you say, take care of your offspring, because say there's a disease that comes around, Like, no matter how good you take care of your offspring, a disease that comes hit you, there's nothing you can do about that.
But if you have fifty.
Thousand offspring and one or two of them have a genetic mutation where they manage to avoid this like devastating disease. Then your genes get passed on and it doesn't matter that you were a terrible parent hypothetically, But of course obviously we do have all kinds of parenting right in nature, and so it does mean that there have been stable patterns of both our and case strategists being.
Able to survive.
But it's just that there isn't one single strategy that always wins. The species that we see alive today have not been raining the earth for the past, you know, millions of years, Like, so many species have gone extinct or have turned into a different species that survived to today. So like there's a lot of strategies that were tried and then then failed, and then a little different strategy was tried and failed. So it's really just about cannas. Species find an amount of stability for a certain chunk of time, and then that lasts for some amount of time, and there's no guarantee that any of the current survivors now are going to last the next million years.
I think it's interesting that you talk about like good parenting and bad parenting. It's funny to put these sort of like moral labels on it, and we joke a little bit, but you know, it makes me wonder if you're the parent in a species where you just sort of like make a lot of them and spraym into the environment and ignore them, do you still love your babies or is it just like not a bigger part of your life.
Sometimes you eat them, sometimes you eat them, sometimes you eat them.
You love them for dinner.
There are a lot of like amphibians and fish that will sometimes eat some of their offspring just like it's fine if I nibble on a few of them, right, But again, it's not because they're cruel. It's because of the trade off between your own personal survival and health and being able to bear future offspring and your offspring surviving in fact, like there are some species of animals that will like fight to the death to protect their offspring, Like I've seen elk try to stomp the dickens out of a mountain lion to save her offspring. Whereas some animals who have a higher fecundity, like they see a predator and they're like, all right, I'm out because I can have babies in the future.
Well, we have hit optimum dKu episode here because we've talked about poop and cannibalism. But we're still going to go ahead and do one more session even though we've hit all the high points. So let's go ahead and take a break, and when we come back we will talk more about babies. Before the last break, Katie was talking about variability and parental care, how some animals are willing to risk their lives and some just aren't willing to risk their lives for their babies. One of the things that got me really excited about behavioral ecology was that even within species, there's a lot of variability, and trying to understand why some animals are great parents and some are kind of miserable is just fascinating to me. Like I studied small mouth bass for a while, and after the ice would melt off the lakes in Wisconsin, it was still absolutely frigid. We would jump in and we would try to find every nest in this northern Wisconsin lake and some of the males you would approach their nest and you could see just like the sh sho of them as they ran off and the minnows would come in and they'd try to eat their eggs and you just would never see that mail again. And then there were other males who you'd be like trying to figure out where the nest is, you haven't even located it yet, and they would literally like torpedo you in the face and knock your mask off and like, you know, knock your snorkel out of your mouth, and they would just keep like ramming into you. So even within species, there's loads of differences, and I don't think we understand very well what those differences are. Sometimes it has to do with how big the males are. So like, if a male is huge and all of the predators in the lake have little mouths, then he can be pretty sure nothing's going to be able to eat him, so he might as well attack. Whereas if you're the little guy, maybe you don't get gutsy until you grow for a few more years, until you're big enough that probably nothing can eat you. But there's loads of variability even within species, which I think is just totally fascinating and adorable.
I mean that reminds me of like sort of different mating strategies where you have sort of sneaky males versus large sort of job males, like in salmon and coho salmon, like there's the jacks, which are the little guys, and then the hook noses, i think based on the shape of their face, which are the bigger ones. And the little guys actually do a really good job of sneakily mating with females, whereas the big guys they may have a more like secure position in terms of not being preyed upon, but they're less agile, and actually the jacks tend to be more numerous because what happens is the female will depositor eggs and the jack kind of like zoom out there and puts the sperm on the eggs and then zooms away right like an.
Egg assass and just like boop, like fertilized.
But yeah, it's also like even a single individual can change their strategy based on say, environmental stressors like kangaroos and wallabies can basically control when they have offspring. It's called embryonic diapause. So it's like when they freeze the development of their embryo when they feel like stressed or like the conditions aren't right, so they're controlling their fecundity. There's also what we mentioned earlier about cannibalism, like eating your eggs, eating your offspring when resources seem limited or when you're stressed out, like bears will sometimes do that, Like bears will eat their newly born offspring like black bears, and it's like, well, why would they do that, Well, if it's a weaker offspring, or if they're stressed out and they feel like resources aren't good at that time, they actually control whether or not they want to invest in an offspring at that point.
Tough decisions. Our kids don't know how lucky they are to have made it as far as they did that we never snacked them right, even when things were scary.
They think it's terrible when parents eat their chocolate bunnies, and they don't know it could be so much.
Worse, so much worse. I'm gonna have to tell my kids that around here. Yeah, it'll be good. I'm a great parent. So to get back to RNK strategists, so we have kind of given some examples of different rn K strategists over the course of this chat, Haiti mentioned that insects are the classic R strategists and just like a funny aside. I could never remember if the rs and the k's, which one was the fast and lots of babies and which one was the slow and just a few babies. And this morning, my really embarrassing way of remembering was Kelly starts with K and I only had a few babies. And so anyway, anyone needs to remember that in the future, just think about Kelly only had two babies. But anyway, that was also my way of remembering if I was going to Slovakia or Slovenia to give a talk, Slovakia has a K in it and Kelly's going.
I remember it with a rapid fire for our and quality with K because I'm good at spelling.
I love it.
Okay, so you and our notes have a really great explanation of whale parental care. Do you want to chat about them as like ideal K specialists?
Yeah? Absolutely so.
Whales are, especially the largest whales. Blue whales are an excellent example of K strategists, right like they fit into the classical. They're big, they live a long time, they're intelligent, and they have a very long gestation period of about a year, and they only have an offspring every presidential term essentially like every four years or so. So they are very slow in terms of producing a lot of offspring, but they pour a huge amount of resources into the offspring. They produce about fifty gallons of milk per day.
That's incredible.
Yeah, it's also really high quality milk. It's very very fat dense.
Is it delicious?
You know?
I would love to try some hot fresh whale milk. That sounds very good, especially because we know what their diet is, Like a ton of krill that's got to have a nice fishy aftertaste.
Wait, how big is a blue whale nipple? I mean, could a human even actually like get it fresh from the whale?
You know, I've actually never seen a blue whale nipple, so I don't know. I'm gonna assume it's pretty big.
If I google that, am I going to get on some terrorists watch list? Right now? You know?
I did once google elephant breasts, and I'm sure I'm on a list. Oh no, But I meant literally elephant breast because I was curious about breastfeeding and elephants.
And I can't explain everything.
Since we're on the topic of Katie's weird history, what is the most interesting animal whose milk you have had?
Oh? I mean, I think just goat milk.
I'm not very exciting. I haven't done anything too adventurous. I wish I could say, like I've suckled on a sicilian or something, but no, I really haven't.
Oh, goat milk. I guess human milk though.
Right, milk is pretty weird.
Human milk's pretty weird, but we all drink it as babies.
I lived in a small village in France where the grocery store had pony milk available, Yes, little bottles of pony milk.
Like from specifically ponies. Like, okay, why not?
I was.
Really it wasn't very good.
It was too horsy for me.
Yeah, okay.
You know how a milk sort of reminds you of the odor of an animal, like goats, so it tastes like the way goats smells a little bit. Not a fan of the way horses smell.
I feel that I definitely can only handle a certain amount of goat cheese before I'm like, I feel like I'm eating the smell of the.
Goat exactly, like I'm licking a sweaty gat or something.
Yeah, it smells and tastes like hay to me, and I love it. But anyway, let's get back.
To blue whales all right, So blue whale milk probably tastes like blue whale, and the calves actually gain hundreds of pounds of weigh every few days.
Incredible.
They grow at an incredible way. They go from being about the sights of like a shipping container to like nearly a football field, right, So it's wild. It's a wild amount of growth. So this also highlights sort of the interesting trade off between somatic growth, meaning growing yourself and growing your offspring. Whales spend their first parts of their lives just grow, growing themselves to enormous sizes by drinking a huge amount of their mother's milk, and then when they're old enough, they start to filter feed on krill. They're balen whales. They have those bristle structures in their mouths. They take in huge amounts of sea water and then expel it all out, and then krill, which are hugely inbundant of a huge source of biomass, get caught in their bileen and then they can swallow that and just they eat. They're like vacuums that are able to exploit a massive amount of biomass in the ocean. It'd be like a cow on land that's just giant and had like a giant sort of like lawn mower mouth that could go and like mow an entire field and like a few hours.
Why hasn't evolution come up with that yet?
It's coming.
Giant, terrifying cows are coming, I'm sure, and they'll be shaped like crabs based on other patterns in nature.
But we just had an interview with the woman who wrote the review paper and how grumpy she is about how it's been interpreted. But anyway, crab episode coming soon.
I stand firmly behind my crab carsonization of cow's theory.
Excellent.
But yeah, so after this period of growing the self to these enormous sizes, then they can enter into the reproductive period and then spend a lot of resources developing the offspring, taking a year to develop the embryo to becoming the live born offspring, and then just feeding it huge amounts. Basically, they inhabit this evolutionary niche where they invest their resources into being really big, and then when you give birth, your offspring has taken a whole year to develop inside your massive body. So there's very few predators who could actually target your offspring, and honestly, they had very little in terms of competitors and predators until humans figured out how to fashion a harpoon. And that we liked whale juices for a lot of disgusting use.
Is that sounds like a title for a great book, Whale Juices for Disgusting uses.
Whale Jesus for Disgusting uses a very highly unethical guide to using whale Ambergriss.
Yeah, Okay, So we've talked about insects being amazing r strategists. We've now talked about blue whales being amazing case strategists. And now that you feel like maybe you've got this strategy in your mind, I'm going to go ahead and tell you that this probably does not represent reality because it's more of a spectrum when you look into these things, and it's, you know, not surprising that things don't fit into little categories because probably the only thing in an environment that matters isn't like how often a fire passes through. And so usually when you find species, you find some like combination of these different kinds of traits. So a classic example is an elm tree. So an elm tree is kind of like a case strategist in that it lives for a really, really really long time and it gets huge. And why it to get huge is because it is competing with the other trees in the canopy. And if you can't get to the top of the canopy, you don't get light and you don't get to survive. And Daniel, this sort of addresses your question earlier about like, well, why wouldn't you always just have a few offspring that you invest a lot in? So for these seeds, they make loads of seeds. I think they can make up to a million seeds in their lifetime. And these seeds are tiny, and the only way any of those seeds get to survive is if they happen to end up in a spot on the floor where they get really lucky, Like maybe a super old tree that's one hundred years old has finally fallen over and died, and now there's a little bit of light coming through the canopy making it to the forest floor, and your offspring just don't have any chance to survive unless they end up randomly in one of those spots.
It's like waiting for a physics professor to retire and open up a professorship.
Finally, right, or answer your emails.
Yeah, it's completely random, Yes.
Completely random, and so like if you had made five of the greatest acorns in the warld Oh, thank.
You, My acorns are wonderful.
Yes, okay, a lot of squirrel energy over here. I don't know why.
Yeah, that's right.
I'm just trying to imagine what is it like to be a good elm parent, Like you know, you're really craft these acorns, or dold you just care deeply about them, or you're like weirdly irrationally proud of your acorns. I don't know. I was trying to do it.
And the promorphizing trees. I never could say that word without first stumbling and overthinking it. But also, if you make like giant seeds, they're gonna get eaten by squirrels, and so just for a variety of reasons, the best strategy is to make lots of them every year and scatter them as far as you can and not care and not care. It seems like there's really no better strategy than that, and the environment is selecting for that.
An animal equivalent to the elm tree are actually a sunfish. They're huge, huge fish, like the size of a kiddie pool, and they're those weird guys that are kind of like flat and they've got the big eyeballs and they're really funny. But you would think, like, okay, there huge so that they can have large offspring that like nobody messes with. But actually their offspring are teeny teeny tiny. They're only a couple millimeters big. They're nearly like planktonic, and they have huge amounts of them. The females can lay like millions of eggs in her lifetime, and so it's kind of like the elm situation where they're just doing like I'm just gonna scatter a bunch of them. It's a little less clear why they do this versus the elm right, because it's not the same situation where the elm seeds need to find that perfect location where they don't have to compete with other trees to get sunlight through the canopy. But in the ocean you have a lot of evolutionary pressures where it's hard not to get eaten and the ocean and it also takes a lot of resources right to create a large offspring. So for these sunfish, even though it seems like they're going towards the blue whale strategy of like, hey they're big, right, so maybe it's so that they can just invest a lot in one offspring. No complete opposite, just a bunch of tiny babies that get eaten up like little popcorn and then like some of them though, happen to keep growing and growing and growing until they're just enormous.
So, Kelly, if we think that the R strategy in case strategy is a little too simplistic, how we like upgraded our model to understand this in terms of like more variables, and it's sort of a higher dimensional evolutionary space.
Yeah, so now we talk about life history strategies, and the decisions that animals make are things like when do you start breeding, how many times in your life will you breed, how many offspring do you make each of those breeding attempts, and how much do you care for them? And evolution has happened upon a lot of different answers to all of those questions, and it depends on lots of stuff like how competitive the environment is, how much food is available, how many other individuals are in the population, how stable is your environment, et cetera, et cetera. There's a lot of different factors that sort of go into these decisions, and so the way we think about it right now involves a lot more variable and it's quite a bit more complicated.
Yeah, it's complicated.
It's just like the Facebook message, you know, Like that's basically like all these mathematicians, all these evolutionary biologists trying to get it down to some nice, beautiful formulas, and the best we can come up with is it's complicated.
In my mind, there's sort of two possible scenarios, or maybe a spectrum of them, one in which, like, it's complicated and it depends on lots of factors, but if you knew all those factors, you could understand it, and you know, everybody is responding to those factors in a way that makes sense to us. And the other is that it's just kind of random, like does everything have to have a reason, Like, you know, you might ask why are there so many different kind of eye colors in humans? Is there a reason why that is? Or just sort of like, hey, these are the group that survived and a lot of it is just random. How much of it does need to be explained. How much of it can we just say, hey, this is sort of just what happened.
Yeah, so that's a great question. I mean, I think we are, over time having a better understan standing of what factors you need to think about ahead of time. If you were to predict, like if somebody plopped a brand new species in front of you, we could ask a certain set of questions and have a pretty good guess for what that animal should do. And it depends a little bit on like evolutionary trajectory. If it's a mammal, then probably female's going to be the one who's doing a lot of investing. So you'd predict that the males would try to mate with as many females as they could to maximize numbers, and then the females are going to have to invest a lot more heavily in the offscoing that they have, and so it is becoming more of a predictive science. But it's taken a lot of work.
Let's say you, Katie, evolution is really interesting because you always have an element of randomness, right, Genetic mutation is random, although geologists would disagree, right, an earthquake is quasi random, right when it comes to animals, Like an animal certainly can't predict when an earthquake happens or some like dramatic environmental change happens. You know, sort of like whether or not you're just in the right place at the wrong time or the wrong place at the right time. All of those things are these random things. But when you have a system over long, long, long periods of time, that's when randomness starts to get shaped into something that seems more intentional, seems more like, oh, this feels like this is becoming more and more efficient. But the truth is that the species that we see today, we are just sort of lucky enough to have this glimpse of the earth at this period of time where we have all these species, and they are not like ideal optimized creatures in every sense, right, Like a lot of the evolutionary traits that they have, like some of them have been selected for, and some of them have been either initially selected for and then evolution switched up on them, right, like where their environment switched up and the strategy has to switch. But they never got rid of it, right because it either wasn't harming them or they just never lucked into the gene that helped them get rid of it. Right, So evolution doesn't create perfectly optimized, streamlined animals, but it does create animals that, generally speaking, are good at survival. And so there's like some potential randomness right where it's like, just happened to be.
That this basically worked.
It's like an old car that's like, yeah, it's got pretty bad mileage and the carburetor makes a weird noise, but it's still going. And there are species like that where it's like it's not perfect, but it's still going.
Some of it can be a little bit random and certainly not perfect.
Yes, I feel not perfectly suited to my environment much of the time. And on that note, Daniel, did you want to ask an alien related question? Or are you good?
Oh my gosh, The answer to that is always yes.
All right, we can pull back. Do you want to ask your alien question?
Green is the answer, green, Miakati?
My question is what color are alien nipples?
You know what?
I've always imagined them as lavender, not funny.
Maybe they also taste like lavender.
Yuh hey, you know what, We're getting into some real strange territory here.
Right.
Thanks for being on the show, Katie, Yeah, absolutely, thanks for having me.
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