“Because … if it weren’t successful, then it wouldn’t be there at all.”
“Where would it be?”
“It would be nowhere. It would have disappeared.”
“Why?”
“Why? Because … Because failures disappear. Don’t they?”
“In this case, Julie, I’d rather you answered this yourself. Do failures disappear or not?”
“They disappear. They have to. If a species is here, then it obviously can’t be a failure.”
“Exactly. No matter how strange it may look to us. Thus a flightless bird like the emu, improbable as it seems, is successful—where it is, for the time being. This doesn’t constitute a guarantee for the lifetime of the planet. The dodo was a success—where it was, when it was. Then conditions changed, and it could no longer succeed—where it was, when it was—so it failed and disappeared.”
“I understand.”
“This is a fundamental fact: The community of life that we see here at any given time isn’t just a random collection. It’s a collection of successes. It’s the remainder that is left over when the failures have disappeared.”
“Right.”
“Now let’s return to Calliope. I’ll ask again what your expectation is for the porcuzard.”
“My expectation is that it’s a success, because if it was a failure, it wouldn’t be there at all.”
“That’s right. No species emerges by failing. What the community brings forth are successes—species that are able to cope with the conditions around them. This is why I say that the process we observe here is overwhelmingly likely to be the process observed everywhere. At any given moment communities anywhere will be largely composed of species that work.”
“Yeah, I don’t see how it could be any other way.”
“At the same time, however, any given species in the community might be declining. Come back in twenty years, and it may be gone. But that doesn’t invalidate our general expectations. Any given species may go out of existence by failing, but it certainly didn’t come into existence by failing. No species comes into existence by failing. That’s simply unthinkable.”
“Yes, I see that.”
“Now back to Calliope again. Here is a picture of porcuzard reproductive life. They are entirely promiscuous. Neither males nor females recognize their young, but females recognize their home nest and will nurse any pup in that nest. If a female finds the unguarded nest of another porcuzard inside her home territory, she’ll enter that nest and kill any pups she finds.”
I asked why she would do that.
“Her intentions can’t be known, of course, but killing these pups does in fact tend to increase her own reproductive success. With these pups gone, her own pups are more likely to carry her genes into the gene pool. Do you understand what I’m saying?”
“I think so. Maybe a little vaguely, but I think so.”
“Good. The males follow a contrary practice. As I just explained, a female kills rivals to her pups inside her territory. A male kills pups outside his territory.”
“Why outside rather than inside?”
“Because inside his territory, the pups may well be his own. Inside her territory, the female’s pups are only in her nest. Inside his territory, the male’s pups are all over the place.”
“My head is beginning to swim a bit. How does killing pups outside his territory increase his reproductive success?”
“In a different way from the way that killing pups increases the female’s chance of reproductive success. The male who is moving around outside his home territory is looking for opportunities to mate, and those opportunities will increase if the females he encounters are not currently nursing pups. If he kills off this generation of pups, the next generation of pups will carry his genes exclusively.”
“Wow,” I commented. “So this killing off of pups has nothing to do with population control.”
“The individuals are acting in a way that improves their representation in the gene pool, but of course this way of acting has many other effects as well. When the population is dense in a female’s home territory, she’s more likely to encounter the nests of her rivals—and so is more likely to kill pups. On the other hand, when the population is sparse, the male has fewer mating possibilities in his home territory and so goes farther afield. And, going farther afield, he’s more likely to encounter pups that he will kill. In other words, when the home territory is sparsely populated, the female kills few pups and the male kills many elsewhere. When the home territory is densely populated, the female kills many pups and the male kills few. The overall effect does tend to stabilize the population. Nothing can ultimately succeed if it has the opposite effect.”
“Okay.”
“Now, what is your expectation of this system? Do you expect it to be a success for porcuzards, or a failure?”
This question struck me as rather pointless, and I said so. “The way you’ve set it up, any system would be a success. You could make up anything, and I’d have to say that my expectation is that it works. You could make up a system in which porcuzards don’t mate at all, and I’d have to say that it must work or it wouldn’t be there, would it?”
“A valid objection,” he conceded. “However, this isn’t just some fantasy I’ve concocted. It’s exactly what is observed among white-footed mice, Peromyscus leucopus, such as you might find in forests of the Allegheny Mountains. This isn’t to say that it’s unique to them. Similar patterns are found in meadow voles, gerbils, lemmings, and several species of monkeys.”
“Okay. I guess I just don’t quite see where you’re headed with this.”
“I’ll try to point the way for you. The ways of the porcuzards (or white-footed mice) seem bizarre—until you understand how they contribute to the animals’ success. Perhaps they even seem immoral, something that right-thinking people should put a stop to.”
“Yes, that’s true.”
“I’d like you to see, however, that if you were to convert them to what might seem to you to be a higher, nobler standard of behavior, they would very probably become extinct within just a few generations. To use a bit of jargon, our examination of these strategies reveals them to be evolutionary stable. Imagine that these species as we see them right now are the product of a hundred thousand experiments conducted over a ten-million-year period. During that time all sorts of reproductive strategies have been tested. Many of them have proved to be self-eliminating, like the one you suggested—not mating at all. Animals that don’t mate at all obviously contribute nothing to the gene pool. Generation after generation, those with no tendency to mate do not reproduce. Generation after generation, less and less is seen of this tendency. Does that make sense to you?”
“Yes, of course.”
“During this period dozens of strategies are tested, and those that tend to promote reproductive success are reinforced in every generation, and those that tend to diminish reproductive success are weakened. Does this still make sense?”
“Yes.”
“At the end of this period, what is found is that a single set of strategies has prevailed. When the home territory starts to become crowded, females kill pups in rival nests. When reproductive opportunities start to become scarce, males move out of their home territory and kill pups wherever they find them. An analysis of these strategies will show you why they can’t be improved upon by any others, but this is neither the time nor the place for such an analysis. In the absence of that analysis, I ask you to take my word for it. These two strategies are evolutionarily stable, which means that no others exist that can supplant them. Any other strategy will fail. Individuals that desist from killing pups in the circumstances I’ve described will not be as reproductively successful as individuals that do not desist. This means that any attack on these strategies constitutes an attack on the biological viability of these species.”
“Okay, my head is swimming, but I think I’ve got that.”
“These infanticidal
patterns probably seem quite strange to you. I’d suggest that this isn’t because they’re inherently peculiar but rather because you haven’t grown up with them the way you’ve grown up with other patterns. You’ll never see a documentary about white-footed mice, because they’re just not fascinating cinematic subjects. What you will see are documentaries about big, dramatic creatures like ibex, big-horn sheep, and elephant seals. And these will without fail show you behaviors that promote individuals’ reproductive success. For example, in any film about ibex, you’re bound to see footage of males bashing into each other head-on during the rut. In the same way, in any film about elephant seals, you’re bound to see footage of giant males savagely thrashing one another to contest possession of a harem. People find an amusement in these spectacles that they would never find in the spectacle of a white-footed mouse biting the head of a helpless pup no bigger than a thumb.”
“I can believe that.”
“Nonetheless, the contests of the creatures I’ve just mentioned are no less deadly. They’re just more exciting to watch.”
“True, I guess. But I’m not sure what your point is.”
“I’m trying to get you used to the fact that things that look strange to you are not in fact stranger than things that look ordinary. You’re used to seeing animals being aggressive, so the aggressiveness of mountain goats and elephant seals seems unremarkable to you. But you’re not used to seeing animals killing their rivals’ young, so the infanticidal behavior of white-footed mice seems grotesque and perhaps even shocking to you. But in fact, both strategies are equally grotesque and equally ordinary. I guess you could say that I’m trying to get you to stop looking at your neighbors in the community of life as if they were characters in Bambi—humans in animal disguise. In a Disney animated feature, two male deer clashing heads in rut would be portrayed as courageous and heroic warriors. But a white-footed mouse sneaking into a rival’s nest to kill a pup would surely be portrayed as a vile and cowardly villain.”
“Yeah, I certainly see that.”
Calliope, Part II
I find, Julie, that I have to make some general remarks about competition in the community of life.”
“Okay.”
“Alan and I are exploring the subject of interspecies competition—competition among different species. A certain set of rules or strategies have evolved in the community of life that assure a lively but limited competition among species. Roughly speaking, they can be summarized this way: ‘Compete to the full extent of your capabilities, but don’t hunt down your competitors, destroy their food, or deny them access to food.’ You and I (in case you haven’t noticed) are exploring another kind of competition, intraspecies competition—competition among members of the same species.”
“Yeah,” I said brightly. “Okay.”
“As you can easily notice in the case of white-footed mice, the rules that apply to interspecies competition don’t apply to intraspecies competition. A female white-footed mouse will go out of her way to kill a rival female’s pups, but she would never go out of her way to kill a shrew’s pups. I wonder if you can figure out why.”
After working on it for a while, I said, “The way I understand it, by killing rival pups, the white-footed mouse is increasing the likelihood of her own reproductive success. It will be her genes that go into the gene pool, not her rivals’. Is that right?”
“Perfectly right.”
“Then killing shrew pups won’t give her that benefit.”
“Why not?”
“Killing shrew pups would be irrelevant. The genes of shrews go into the shrew gene pool, don’t they? Am I understanding that right?”
Ishmael nodded. “You’re understanding it right. The genes of shrews go only into the shrew gene pool.”
“Then killing shrews can no more increase her representation in the gene pool for white-footed mice than killing owls or alligators.”
Ishmael stared at me for so long that I began to squirm. Finally I asked him what was wrong.
“Nothing’s wrong, Julie. Your ability to give such an answer simply makes me wonder if you’ve already been studying in this area.”
“No,” I said. “I’m not even sure what ‘this area’ is.”
“It doesn’t matter. You’re very quick. I’ll have to be careful not to let you get a big head. Nevertheless, your conclusion is a bit too sweeping. The white-footed mouse would derive some benefit from killing shrew pups, because the shrew pups compete with her own pups for some resources.”
“Then why not kill them?”
“Because there are thousands of species that compete with her pups for some resources—and she can’t kill them all. There is only one species that competes with her pups totally—for all resources.”
For a second I didn’t see it, then of course I did: “Other white-footed mice.”
“Of course. Killing a nestful of shrews would be of very limited benefit to her. But killing a nestful of white-footed mice represents a clear and undoubted benefit.”
“Yeah, I can see that.”
“This is why the rules that govern competition between species are (and must be) very different from the rules that govern competition within species. Competition within species is always more arduous than competition between species. This is because the members of a given species are forever competing for the same resources. And this is especially true when it comes to mates. Many hundreds of species might compete with a white-footed mouse for a chance to grab a mulberry, but only another white-footed mouse will compete with it for a chance to mate with another white-footed mouse.”
“Ah,” I said.
“ ‘Ah’ meaning what?”
“ ‘Ah’ meaning … now we come back to the rutting battles of the elephant seals and the bighorn sheep. Am I right?”
“Not exactly,” said the gorilla. “Our focus is on intraspecies competition in general—for all resources, not just the reproductive ones.”
“Okay. But … is this really on the main road? Are we still headed toward an explanation of why we turn to spooks and angels and ufonauts to find out how to live?”
“Unlikely as it seems, we’re definitely on that road.”
“Good.”
“Evolution brings forth what works. For example, we’ve already seen that killing rivals’ pups works for white-footed mice. But of course it wouldn’t work for them to kill their own pups. That strategy would never evolve. It couldn’t evolve, because it’s self-eliminating. I’m sure you see that.”
“Yes.”
“Now we’re going to have a look at what works when it comes to conflict among conspecifics—members of the same species. Because conspecifics are constantly competing for the same resources, opportunities for conflict among them arise daily, even hourly. Obviously, therefore, evolution must have brought forth means of resolving these conflicts that are less than deadly. It wouldn’t work to have every conflict over resources settled by mortal combat.”
“Yes, I see that.”
“There are a finite number of strategies that can be adopted by conspecifics in conflict, but it’s not to our purpose for me to develop a complete list of them here and now. Rather, what I’d like to do is pay another visit to Calliope to study the Awks to see the strategies evolution has brought forth among them for dealing with conflict.”
“What are Awks?”
“Awks are a sort of cross between monkeys and ostriches, if you can picture such a bizarre coupling. Originally they were birds, but they became so much at home in the trees that flight became superfluous for them. So they’re rather like ostriches in that they have stunted little wings, and they’re rather like monkeys in that they have very useful grabbing and swinging appendages like hands and tails that enable them to elude almost every sort of predator that comes after them. Unlike many species, in which the male is superfluous after impregnating the female, the male Awk must be on hand to help provide food for newborn offspring. And by the time he’s no longer need
ed as a food collector for the young, the three or four females under his care are ready to mate again. So Awks have a recognizable sort of family life.
“When two Awks come face-to-face over a luscious piece of fruit, here’s what generally happens. They glare at each other and bare their teeth and shriek. If one of them is distinctly smaller than the other, then it will probably give up rather quickly and slink away. But not always. Two out of five times (perhaps corresponding to how hungry it is), it will start bouncing up and down in a clearly threatening manner. When this happens, the other will usually back down, even if it’s larger. But again, not always. Perhaps one out of five times, it will refuse to be intimidated and will try some intimidation of its own, bouncing up and down and snapping its teeth. This will usually send the other off with its tail between its legs—but again, not always. Perhaps one time in ten, the smaller will recklessly continue to threaten the larger, and they’ll end up in a physical battle that will last twenty or thirty seconds and will result in a few minor cuts and bruises before the victor carries away the fruit.
“The strategy each Awk is following can be expressed roughly as follows. ‘If confronted by an Awk competitor, be aggressive, but back down if the other is distinctly bigger—unless you really need the resource in contention, in which case you might occasionally try being a bit more aggressive just to see if the other will back down. If the other responds by becoming more aggressive, run away, unless you really need that resource and are feeling lucky.’ Now of course I don’t mean that this strategy is something reasoned out. But if it were to be reasoned out and articulated in words, then it would be something like that. The Awks behave as though they were following a consistent strategy, roughly as I’ve described it.”
“I understand.”
“Now this sort of behavior isn’t at all unusual. Most earthly species resolve their conspecific conflicts over resources in just such a fashion. It doesn’t pay to get into a serious battle over every acorn, but it also doesn’t pay to back down over every acorn. It’s important to be predictable to a certain extent, but it’s also important not to be too predictable. For example, your opponent should know that when you start snapping your teeth at him, you’re pretty likely to attack. On the other hand, your opponent shouldn’t be able to count on your backing down just because he starts snapping his teeth at you.”