In March I talked about the mystery of the self-sacrificing worker bee, pointing out that the worker dies after she delivers a sting. At first this was thought to be a problem for Charles Darwin’s theory of natural selection – that some individuals would give up reproducing in favor of helping another reproduce, even to the point of self-sacrifice if necessary – a situation called altruism. But by the mid-20th century and with an understanding of hereditary genetics, it was shown by W.D. Hamilton that such extreme forms of altruism can be explained if an individual’s behavior results in a high percentage of her genes being passed on to the next generation, even if those genes occur in the bodies of near kin. Thus, overnight was born the theory of Kin Selection to explain altruism and extreme sociality in insects and other organisms. In the case of ants, wasps and bees, a peculiarity of this group is the fact that males have only one set of chromosomes instead of the usual two. For reasons I explained in the March column’s sidebar, this irregularity means that a worker bee shares 75% of her genes in common with her sister, compared to only 50% with her sons (in the event she becomes a laying worker and produces sons). This means that a worker is more related to her full sisters than she is to her sons – much more so; therefore it makes sense for her to concentrate on helping her mother reproduce more sisters. In 1964 this was seen as a triumphant answer to the problem.
Now at this juncture I want to take a sharp digression to tell a story that many of my readers may relate to. It’s happened to me a lot of times, but this was the first, early in my career, and I wasn’t very experienced. It was a warmish early-spring day and my office telephone rings.
“Hello, is this the Entomology department?” asks the male caller.
“Yes it is; this is Keith Delaplane.”
“Well hey there Mr. Delaplane, I was wondering – is there someone there who could tell me how to keep bees?” he asks with breezy optimism.
I thought it was a joke.
“Yeah, you know. Honey bees,” and hesitation creeps in, “In hives?”
“Are you serious?”
“Umm, yeah. Is now not a good time?” and after a pause, “Maybe I should call back later?”
“No, no I mean – “ I’m scrambling to recover at this point, “I am the person you need to talk to. It’s just that – well, let me see what I can do.”
And I spend the next few minutes gently steering the caller toward beginners’ resources, local bee clubs, upcoming workshops, books to read, videos to watch, and in general planting the idea that beekeeping is not some simple thing you can pick up with a phone call. I have since learned that it’s an easy temptation to fall into – the presumption that some new pursuit or bit of knowledge can be self-contained, easy to grasp, and fixed once we learn it. We want to cling to our naïve understanding of things and resist revising our opinions. If I ever have the chance to coin a proverb it’ll be something like, “It’s never as simple as you think it is.”
That’s certainly true for Hamilton’s early explanation for altruism that I wrote about in March. Since 1964 and beginning with Hamilton himself there have been entire libraries written to expose new problems, form new hypotheses, test them, and in general fill in the gaps with nuance and revision.
For starters, the overwhelming 75% relatedness celebrated between worker full sisters applies, well, just to full sisters. When it comes to the other product of a worker’s altruism – her brothers, male offspring of their common mother – the degree of relatedness drops to only 25% (see sidebar). Over the course of a season a worker will help rear roughly the same number of brothers (0.25 related) as supersisters (0.75), so that her genes passed on to the next generation average out to 50% – the same as if she had elected to reproduce herself.
So naturally one wonders if we’re back to where we started – why practice altruism and sacrifice my own reproduction if the net transfer of my genes to the next generation is still 50%?
To begin, let’s note that 50% is still pretty darn good, and it wouldn’t take much to tip the balance one way or the other. The alternative for our hypothetical ancient honey bee ancestor is to go it alone – forego altruism, make her own nest, rear her own brood. But last month we talked about the advantages of nesting and raised the likelihood that nesting is a necessary condition to social life. Compared to going it alone, sharing a nest and responsibilities for brood rearing, foraging, and defense don’t sound so bad. To quote Francis Ratnieks, “When relatedness is high, even small asymmetries in costs versus benefits that favour rearing siblings instead of offspring can select for helping2.” And by “helping” here he means altruistic helping.
A second issue to face is Hamilton’s presumption that …