In T&R XIV I showed that prejudice against group selection is impervious to evidence from laboratory experiments. It is also impervious to evidence from the wild.
I will focus on one of many examples that can be provided. In 1995, Robert Heinsohn and Craig Packer published an important paper on territorial defense in lions in the journal Science. As good experimental field biologists, they had played recordings of lions from neighboring territories to observe how females of the focal territory responded. They discovered that the same individuals consistently arrived first at the scene while others consistently lagged behind. There seemed to be bravehearts and cowardly lions within the same pride.
Heinsohn and Packer looked for an advantage to counteract the cost of territorial defense for the bravehearts within their own pride and couldn’t find it. The bravehearts weren’t socially dominant, they didn’t have more offspring, and they didn’t punish the cowardly lions, who simply seemed to be cheating and getting away with it. The bravehearts were providing a public good at their own expense, an animal version of the tragedy of the commons made famous by Garrett Hardin in the 1960′s. Here is how Heinsohn and Packer described the situation to the best of their knowledge:
Female lions share a common resource, the territory; but only a proportion of females pay the full costs of territorial defense. If too few females accept the responsibilities of leadership, the territory will be lost. If enough females cooperate to defend the range, their territory is maintained, but their collective effort is vulnerable to abuse by their companions. Leaders do not gain “additional benefits” from leading, but they do provide an opportunity for laggards to gain a free ride.
Let me pair this passage with the canonical passage by Darwin that I also quoted in T&R II:
It must not be forgotten that although a high standard of morality gives but a slight or no advantage to each individual man and his children over other men of the same tribe, yet that an increase in the number of well-endowed men and advancement in the standard of morality will certainly give an immense advantage to one tribe over another. There can be no doubt that a tribe including many members who, from possessing in a high degree the spirit of patriotism, fidelity, obedience, courage, and sympathy, were always ready to aid one another, and to sacrifice themselves for the common good, would be victorious over most other tribes; and this would be natural selection.
I hope you can see the similarity between these two passages. Darwin was identifying what I call the original problem; traits that benefit the whole group are often disadvantageous within the group. The counterbalance for cheating does not reside within the group; it resides in the process of more cooperative groups outcompeting less cooperative groups . Darwin’s example was hypothetical. Heinsohn and Packer seem to be providing a real-world example with territorial defense in lions. They even stress the importance of between-group competition as the primary influence on the evolution of lion sociality.
Before continuing, let me issue two caveats. First, I have the highest respect for Heinsohn and Packer. They are topnotch scientists who can only be admired, not only for conducting such arduous research but also for attempting controlled experiments in the wild. Second, the last word has not been written on lion social behavior. Perhaps they or someone else will find a within-group advantage for bravehearts in the future. I’m interested in how they interpret their current data. They don’t interpret it as a provisional example of group selection. They don’t even mention group selection as a possibility. I doubt that it even occurred to them to regard group selection as a viable possibility, even though a description comparable to Darwin’s flowed from their own pen!
For those who feel impelled to shout “kin selection!” because lion prides are composed of related females, my reply is the same as for the chicken example discussed in T&R XIV. Genetic relatedness explains why bravehearts are clustered in some prides and cowards in others. Cowards still have the advantage within each pride, the observation that Heinsohn and Packer find so puzzling. If they had a better understanding of kin selection seen through the lens of multilevel selection theory (see T&R XIII), they wouldn’t be so mystified by their own data.
This example illustrates a problem that pervades the evolutionary literature. Group selection became such a pariah concept that most people don’t look for it. They haven’t looked for it for so long that they forgot what it looks like and can’t even recognize it when it bites them in the butt! Even when they do recognize it, they are tempted to describe it in a way that doesn’t use the G word to make it more palatable to their peers. In this fashion, our students continue to learn that the rejection of group selection was a triumphant advance for evolutionary theory while the evidence for group selection lies all around us.
Science is no better than political revisionism if this situation is allowed to persist. One reason that I am writing this series of blogs is because I am an idealist about science. I regard it as the best cultural system we have for holding people accountable for what they say. Scientists have a responsibility to keep track of the history of their ideas and to acknowledge mistakes from the past, no matter how large. Unfortunately, like religion, science as practiced often falls short of science as idealized. The group selection controversy is an embarrassment for science and the sooner its shortcomings are corrected, the better.
To be continued.