The Selfish Gene

Dawkins has considered aggressive, parental, and sexual behaviors among survival machines. Now, he wants to address social insects, understand why animals live in groups, and try to make sense of reciprocal altruism, meaning the principle of “you scratch my back, I’ll scratch yours.”

Hunting in a group makes good “selfish” sense, since it makes catching prey easier. Dawkins borrows another explanation from Hamilton, who thinks that running as a herd also has selfish motivations. Animals on the edge of a herd are more likely to get eaten by predators. It’s a good “selfish” strategy for animals to clump into herds and try to get in the middle to protect themselves from predators.

Birds sometimes call to warn other birds there’s a predator nearby. This seems problematic, because it puts the calling bird at greater risk of being eaten. It’s been such a problem for Darwin’s theory of evolution that scientists have thought up all sorts crazy explanations for bird alarm calls, including Trivers who gives five different explanations. It’s likely, for example, that nearby birds are related, so birds protect their genes (in their relatives) when they sound alarms, keeping that trait in the gene pool.

Dawkins offers two explanations of his own. The noise of nearby birds might attract a predator even if one bird is quiet. So, perhaps the calling bird is selfishly trying to warn others to keep quiet. Also, if a bird just flies away when spotting a predator, he actually stands out more as a lone (and therefore vulnerable) bird. Sounding an alarm might be a way to get the whole flock to fly away, keeping the calling bird safely in the middle of the flock, and far from the predator. Dawkins concludes that warning calls have selfish motivations.

It’s harder to explain what genetic payoffs there might be for gazelles who “stot” (bounce) to warn about predators, but draw attention to themselves in the act. Ardrey thinks this is altruism for the good of the group, but Zahavi disagrees. Zahavi thinks stotting warns predators that the gazelle is so fit and strong that she can stot around and still not get caught.

 “Kamikaze” bees die when stinging, which looks on the surface like altruism for the good of the colony, but Dawkins disagrees. Most bees in a colony are sterile, and only sterile bees sting, so there’s no genetic loss involved. In fact, he thinks the colony acts more like one individual. It seems to have collective consciousness, and a communal stomach, for example. Dawkins thinks the queen represents reproductive cells, and worker bees function as organs like the heart, muscles, liver, and so on. He speculates that the death of a sterile bee is like a tree losing a leaf.

Another way to think about social insects is to invoke the “bearing” and “caring” dichotomy. Reproductive insects in a colony are “bearers,” and worker insects are “carers.” Since they are all genetically related, this isn’t altruistic behavior, but selfish behavior. This division of labor keeps all their genes in the gene pool. Hamilton discovered that “the Hymenoptera” (insects including ants, bees, and wasps) determine sex differently. Unfertilized eggs become male worker bees, meaning they actually share all of their genes with the queen and her offspring, so from a genetic perspective, protecting the reproductive bees is better than protecting themselves.

Inspired by Fisher’s research, Trivers and Hare calculated ideal sex ratios in hymenopteran colonies. There is a potential conflict of interest because workers benefit from having more female (reproductive) insects in the colony to pass on their genes, but the queen benefits from having equal males and females, some to reproduce, and some to keep the colony (and the reproductive bees) fed and protected.  In ants, the workers would win out, except ants often take unknowing slaves into their colonies. The adaptive strategies among “slave-making” queens and “slave-taking” queens play out such that reproductive ratios end up closer to what is optimal for the queen: equal males and females. 

Dawkins thinks an art farm (or hymenopteran farm) functions like a gene farm. The queen is farmed for her eggs, and the whole colony is organized to facilitate genes being passed on, packaged in reproductive ants.

Dawkins starts thinking about symbiotic relationships in the natural world. Many ants feed fungi in order to later farm them, for example. They also milk aphids while protecting them from predators. Lichens are “double organisms”—an intimate symbiosis between algae and fungi. The relationship is so close that lichens seem like individual plants. Humans also contain tiny bacteria called mitochondria. Without mitochondria, we would die. And without us, mitochondria would die. Similarly, viruses are parasitic replicators (DNA surrounded by protein) that have bypassed the need to be transferred through reproductive organs. They just hop around from body to body.

Symbiotic relationships, or “associations of mutual benefit” evolve if each partner gets more out the relationship than they put in. Group selection theorists would consider cooperation between species separately from cooperation within species, but Dawkins thinks there’s no need for that. He wonders if reciprocal altruism (for example, scratching each other’s backs to get rid of parasites) has selfish motivations as well. Darwin (and later Williams) thought that reciprocal altruism could evolve in populations that were able to recognize and remember each other.

Trivers looked at this puzzle too, and used the Prisoner’s Dilemma from game theory (the mathematics of strategic interactions) to solve it in 1971. Trivers worked out that in a population with “suckers” (who always pick parasites off others), “cheats” (who accept help but don’t reciprocate), and “grudgers” (who pick parasites off but remember cheaters and don’t help them next time around). Depending on the starting ratio of the population, the group will evolve to be nearly all cheats (and eventually shrink in numbers or die out), or mostly grudgers.  Both are evolutionarily stable strategies.

Trivers also looked at “cleaner-fish,” who have a symbiotic relationship with larger fish. Cleaner fish get their food by nibbling parasites off large fish, and large fish in turn get cleaned. This also seems like reciprocal altruism. The large fish could eat the cleaner fish after they’ve been cleaned but they don’t. Similarly, the cleaner-fish could take bites out of the large fish and swim away, but on the whole, they don’t either. Dawkins suggests that because symbiotic cleaning happens at fixed places in the ocean for each fish species, reciprocal altruism based on some form of recognition might have evolved. 

Trivers also thought that feelings like sympathy, guilt, envy, and gratitude evolved to help humans cheat and detect cheats. Dawkins decides to let the reader speculate about that one on their own.