April 5, 2010
Jacobus J. Boomsma
Centre for Social Evolution
University of Copenhagen
Universitetsparken 15
2100 Copenhagen
DENMARK
Dear Jacobus Boomsma:
I have read your article “Seminal Fluid Mediates Ejaculate Competition in Social Insects,” Susanne P. A. Boer, Boris Baer and Jacobus J. Boomsma, SCIENCE vol. 327 no. 5972 March 19, 2010 page 1506 with something akin to despair. It reminds me of a moment in my youth. We were having a discussion about philosophy, and my father (who actually understood the issues better than any of us) said in a cheerful tone, “It’s existentialism when you think it is just about to make sense and then suddenly it doesn’t.”
Only this time it is fertilization. It was just about to make sense. What I know is that kinship affects fertility. (Got it. Evidence on nobabies.net March 25, 2010. Web site has other evidence, thoughts and correspondence.) Now you have said that sperm in certain species of social insects spend some time in the female before she stores them properly and uses her original supply for the rest of her life. (Got it. We know honeybee queens mate only during one flight. The rest makes sense.) You have shown that where there are multiple matings, the sperm can attack each other before they are stored, the attack evidently being chemical. They put out something that attacks foreign sperm and not themselves. (Makes perfectly good sense. Since kinship is needed for fertility, poisoning non-kin is a jolly good plan.)
But how can they do that? How can a sperm concoct a poison that will effect other sperm but not itself? I don’t think I could come up with a poison that would affect other people and not myself; the immune system takes too long to swing into action. It is baffling how, but the “why” makes sense.
Then comes the game wrecker. The poison these sperm make also works against sperm from the brothers of the insect that made them.
That requires incredible precision in distinguishing others from self. After all, all the sperm in one ejaculate are not alike. And the sperm of two brothers will have very similar chromosomes. I assume that recombination lies at the heart of it. DNA is just too stable to produce enough mutations to make that distinction easily. Could it be that there is a non-DNA form of inheritance at work?
I take a small amount of comfort from the fact that on closer inspection of your data the self vs. non-self difference is above question while the fratricidal vs. xenocidal effect is much weaker. I am tempted to take the cowards way out and just ignore the whole matter. However if something comes to mind you think might be relevant to kin recognition in other species (and you specifically cast doubt on that in the article) I for one would like to know more, although it would probably simply add to my bafflement.
Sincerely,
M. Linton Herbert
There have been 3,755 visitors so far.