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Chatper 10: You Scratch My Back, I’ll Ride Yours
Continuing to blog my way through Richard Dawkins’ classic, The Selfish Gene, I’ve arrived at Chapter 10, which is about animals living in groups.
Most fascinating for me was how the Selfish Gene idea relates to altruism in the social insects classified as hymenoptera. What makes these bugs such oddballs is their asymmetric degrees of genetic relatedness. Quoting Dawkins:
“A hymenopteran nest typically has only one mature queen. She made one mating flight when young and stored up the sperms for the rest of her long life — ten years or even longer. She rations the sperms out to her eggs over the years, allowing the eggs to be fertilized as they pass out through her tubes. But not all the eggs are fertilized. The unfertilized ones develop into males. A male therefore has no father, and all the cells of his body contain just a single set of chromosomes (all obtained from his mother) instead of a double set (one from the father and one from the mother) as in ourselves. …
“A female hymentoperan, on the other hand, is normal in that she does have a father…”
A male gets 100% of his genes from his mother, so the Selfish Gene hypothesis neatly explains why males sacrifice all for their queen. From the standpoint of a male’s genes, saving the life of his queen is exactly equivalent to saving his own life. In fact, it’s better because she will continue to pump out more copies of those genes for the rest of her life.
Things get even more interesting with the sterile females (the “workers”). On average, a female shares 3/4 of her genes with her sisters. That’s because they have identical genes from their father (remember, he only had one set of genes to contribute), and an average 1/2 of their mother’s genes in common.
Although sisters share 3/4 of their genes, their mother passes only 1/2 of hers to her daughters (the father contributing the other half).
Thus, females are more closely related to their sisters than to their offspring! Selfish gene theory correctly predicts that they would be willing to forego having babies, and devote their lives to caring for each other instead.
If you want to read more about this, you can google eusociality. Wikipedia’s article has a helpful section on its evolution. (They observe that Darwin was puzzled at how it could have evolved, but correctly anticipated that a rationale might be found someday. That day arrived with the synthesis of Mendel’s discoveries in genetics and Darwin’s ideas of natural selection.)
There’s much more in this chapter, including birds who are willing to call a predator’s attention to themselves by raising an alarm to their flock, ants and aphids in symbiosis, and animals that invest energy grooming each other.
The upshot is that many examples of altruism that seem to be contrary to evolution are anything but.
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