“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.”