Selfless Genes

By Bob Holmes
New Scientist, March 9, 2009

Edited by Andy Ross

According to Richard Dawkins, the genes that do the best job of passing themselves along to the next generation are the ones that flourish. But some evolutionary biologists argue that this view leaves us blind to crucial evolutionary processes among groups, species, and even ecosystems.

Entire species can have traits that, over geological time, make them more likely than others to survive. This can lead to evolutionary change that could not be predicted from individual adaptations alone.

Species selection may help explain some puzzling observations. For example, larger individuals often outcompete smaller ones, so selection at the level of individuals would tend to favor large body size. But a larger-bodied species has a larger requirement for food and space, and so might run greater risks. Species selection may oppose individual selection to help keep body size constant.

Species are stable enough over time for selection to have some effect in shaping their characteristics. In contrast, most evolutionary biologists have difficulty accepting that natural selection can act at an intermediate level to select groups.

Many lab experiments have shown that group selection can lead to evolutionary change. But in nature, cooperative groups are vulnerable to takeover by cheaters. These selfish invaders pay none of the costs of cooperation yet reap the benefits. David Sloan Wilson has shown that cheaters will not prosper if groups frequently break up and reform again with new members. Each fresh start favors the groups with the fewest cheaters.

Evolution can make the conditions needed for group selection more likely in the future. Group selection may sometimes favor the interests of a group over any of its constituent individuals, and ecosystem selection might act to shape an entire ecosystem over the interest of its constituent species.

According to this hypothesis, just as the cells within our bodies sometimes sacrifice themselves to ensure the body as a whole remains healthy, so individual species within some ecosystems may on occasion make sacrifices to ensure that the whole ecosystem survives. Still, the mainstream view is that individual species in an ecosystem are like cancerous cells in a body, growing as aggressively as possible and heedless of the cost to the ecosystem.

Genes operate as part of networks of interacting genes, in which multiple genes affect each trait and each gene affects multiple traits. These networks usually have enough redundancy that deleting any one gene has little if any impact on an animal's form or function. So it is the network that is selected, says Eva Jablonka.

Dawkins says that only by looking at the fitness of the genes themselves, averaged over all their possible contexts, can one really understand evolution. Genes carry information in a stable form from one generation to the next, usually changing only slowly, while individuals, groups, and species come and go.

Wilson on Altruism

By Leon Neyfakh, April 17, 2011

Natural selection means that the fittest pass down their genes to the next generation, and every organism would seem to have an overwhelming incentive to survive and reproduce. Yet self-sacrifice exists in the natural world. By identifying the mechanisms through which altruism and other advanced social behaviors have evolved, we stand to gain a better understanding of human civilization.

The currently accepted explanation for altruism is William Hamilton's theory of kin selection theory. It says that an organism trying to pass its genes down to future generations can do so indirectly, by helping a relative to survive and procreate. Acting altruistically toward someone with whom you share genes is just a different way of promoting your own genes.

Harvard biologist Edward O. Wilson argued in a paper in Nature last August that kin selection theory doesn't explain altruism. That paper, co-written with Harvard mathematicians Martin Nowak and Corina Tarnita, is now being challenged in letters, blog posts, and rebuttals in other journals. Richard Dawkins: "It's almost universally regarded as a disgrace that Nature published it."

Wilson made Hamilton's theory the basis of his work in sociobiology. But over decades he came across evidence that made him doubt the connection between genetic relatedness and altruism. His alternative theory holds that the origins of altruism and teamwork have nothing to do with kinship. Under certain circumstances, groups of cooperators can out-compete groups of non-cooperators. This group selection is the basis for a variety of advanced social behaviors linked to altruism, teamwork, and tribalism.

Many biologists are baffled by the attack on the mathematical equation underlying Hamilton's theory. According to Nowak, the critics don't understand the math. The equations underlying kin selection theory can't be used to explain the natural world. Nowak believes that many of the people disputing his paper have never actually done the math.

Critics feel Wilson and his coauthors are wrong to treat kin selection as something separate from natural selection. As Dawkins explains it, kin selection is not a distinct process but a necessary consequence of neo-Darwinian natural selection.

Wilson argues that advanced social behaviors like altruism are evolutionarily advantageous on a group level. That socially advanced organisms end up favoring their kin is a byproduct of their group membership, not the cause. Wilson plans to extend his new ideas about the evolution of social behavior to humans in a book next year.

AR  Interesting topic, and relevant to my argument in G.O.D. Is Great.