The Hive Mind

Feature / by Benjamin Phelan /

Is understanding the selfless behavior of ants, bees, and wasps the key to a new evolutionary synthesis?

Bernard Crespi, an evolutionary biologist at Simon Fraser University who has described a form of eusociality in insects known as thrips, disagrees. “Ed Wilson is known for making some controversial statements about humans in the ’70s and ’80s, but he never made a mark on the evolution of eusociality,” as, Crespi says, his contemporaries Hamilton, Charles Michener, or Richard Alexander did. “It’s causing confusion in the field. It’s not a conceptual advance.”

Others are more blunt. “I have a feeling it’s a waste of time,” says Laurent Lehmann, an evolutionary biologist at Stanford University who builds mathematical models describing the spread of altruistic traits. “And it’s not even clear to me what the Wilsons want. It’s a lot about semantics, not scientific issues. They’re not using clear definitions, not referring to the math, not referring to the work that has been done. Once you define the terms correctly, there is no problem.”

Lehmann is alluding to the well-known if confusing fact that multilevel selection and kin selection have been shown, time and again, to be mathematically identical. The theories differ in how they interpret what the math describes —  selection among relatives or selection without relatedness — but saying that they are different, says Lehmann, is playing word games, and obfuscates the deeper truth.

E.O. Wilson agrees, though to him the other side is playing grammar police, quibbling needlessly over the correct interpretation of the different shades of altruism that occur in insect society. In any case, he says he was prepared for reactions like those of Crespi and Lehmann and expected feedback both favorable and outraged. But inclusive fitness hasn’t, he says, described what happened with the evolution of eusociality: “It’s what I call going up the rough side of the mountain,” Wilson says. “There’s another side, and this is what I like to call the new paradigm. I know I irritate people.”

So with E.O. Wilson’s imprimatur on multilevel selection, a dispute from the 1960s is reanimated: What is the correct theoretical interpretation of the process of natural selection? Why does it occur, and on what level? Are groups more visible to natural selection than individuals? Than genes?

These questions are of great importance to the theoretical underpinnings of evolutionary studies. But theoretical questions are no longer the only game in town. Now that investigators can sequence colossal amounts of DNA and directly observe gene expression, evolutionary studies bear little resemblance to the field that Karl Popper once called, with justification, “a metaphysical research project.” When it comes to the problem of eusociality, theory has been a fruitful guide to research, but no mathematical picture of biology has yet provided an unassailable explanation for how the elaborate social system evolved. Emerging experimental approaches to evolution that combine a number of molecular techniques for studying development with the gene-centered evolutionary synthesis represented by Hamilton, are providing everyone, kin selectionists and group selectionists alike, with new insights into how selfless eusociality could evolve. Whether it will mean the end of the story is another matter.

From the beginning, altruism has been difficult to describe in evolutionary terms. E.O. Wilson, writing in Consilience, called it “the central problem of sociobiology.” Darwin considered it too, and found in the existence of morality a different manifestation of the same phenomenon that leads ants to care for the offspring of others and to forego procreating.

In The Descent of Man, Darwin wrote that while moral behavior was unlikely to give any benefit at all to the person performing it, “an advancement in the standard of morality and an increase in the number of well-endowed men will certainly give an immense advantage to one tribe over another.” The children of dead parents will be fed and reared by virtuous neighbors. Because of individual sacrifice, wars will be won. And so, he reasoned, groups of altruists will always outperform groups of individualists. That moral behavior exists, and is important enough that something as abstract as culture has grown up largely to enforce it, was proof to Darwin that sometimes evolution acts at the level of the group.

“When you look at pro-social behaviors,” says David Sloan Wilson, “behaviors that are for the good of the group, they’re not locally advantageous. If you’re an altruist, and you’re doing what’s good for the group, that fundamentally requires time and energy and risk on your part. If your neighbor isn’t doing that, then these behaviors are locally disadvantageous. We have a problem here. How do these traits evolve when they are less fit than the traits that we associate with selfishness and free riding? That’s the dilemma.”

It would appear that altruistic traits should quickly become rare and go extinct, since altruists always fare worse than their selfish neighbors. They expose themselves to the danger of death while the selfish save their own skins, simultaneously benefiting from the protective behavior of the altruist. But altruism is everywhere. Somehow, evolution bridges the gap between the individual, where altruism dies, and the group, which it vivifies.

For Sloan Wilson, the solution is straightforward: Altruism is advantageous at a larger scale, and that is the scale at which natural selection selects it. Altruism is good for the group; therefore its evolution and persistence are inevitable. Stir in population genetics, he says, and you can call it a day. “We’re done now,” he says. “Let’s go home and have a beer.”

Well, he admits, it’s not really that simple. Group selection can be so counterintuitive that a generic version of the problem, a situation in which a given trait is declining at one scale but becoming more common at another, has a name: Simpson’s Paradox, for a mid-20th-century British statistician who noticed it.

A well-known instance of Simpson’s Paradox occurred in the 1970s, when the University of California at Berkeley was sued for sexually discriminatory admissions practices. An analysis of its rolls revealed an ambiguous situation in which sexual discrimination clearly did not exist in individual departments, which were fair and equitable in the percentages of women versus men admitted, but just as clearly did exist at the level of the institution, where acceptance rates were blatantly sexist. The paradox resolves in this case because greater numbers of women applied to smaller, more selective departments, and men to larger, less selective ones. So because male-dominated departments were larger, more men were admitted to the university. “It’s sufficiently counterintuitive,” says Sloan Wilson, “that you kind of rub your eyes after you work through the example. [Group selection] is actually the same kind of process, by which altruists can be at a disadvantage in every group, but nevertheless increase in frequency in the total population because the group with the most altruists is contributing differentially to the total.”

Sloan Wilson has developed a number of tools to model trait distribution via multilevel selection, such as the trait group and the structured deme. But the first few generations of group selectionists were not terribly sophisticated. To be fair, says Sloan Wilson, the early version of group selection wasn’t much of a theory, and it deserved to be scrapped. If a trait appeared to benefit a group, that was enough for the group selectionists of old. It wasn’t all that important to explain how altruistic traits overcame steep selective gradients because, clearly, they had. In the hands of some practitioners, group selection was nothing more than a tautology, and one didn’t need to understand the mechanism of inheritance for, or even the nature of, the trait that was under study.

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