Penis Fencing: Dangerous or Decadent?

I’ve gotta, say, Roughgarden’s The Genial Gene is so far pretty awesome. It is fulfilling its promise of being meaty, laying out the real some real testable predictions for her theory of Social Selection, and also pointing out some of the logical, historical, and cultural fallacies of sexual selection. I’m going to be very curious to read some of the reviews that will come out by sexual selection advocates, but so far, I think she is presenting a fairly compelling argument.

I just finished reading a section on penis fencing in hermaphroditic flatworms. The example was used to demonstrate how we write the narrative that we want to see – virile strong rapacious flatworms, dueling it out! The loser slinks away in shame to bear the burden of being a female. The winner is victorious, not having to incubate their own genetic progeny, but instead have farmed it out. It’s inspired papers such as Sex and Violence in Hermaphrodites (which shows that insemination is usually dominated by one individual, but doesn’t show anything about multiple copulation attempts, or the cost of being inseminated) or Evolutionary Conflict: Sprem Wars, Phantom Inseminations (about sea slugs, but, again, no fitness benefits v. costs). It’s also inspired at least one great comic strip.

There are a few questions this raises. First, if such a system of mating is SO harmful, then wouldn’t it be selected against? I mean, if “losing” a mating bout is such a huge cost to an individual…which implies a cost to their fitness, then selection should ultimately find a way around that? It doesn’t sound like the most evolutionarily stable of strategies – hurt the one who will bring your genetic contribution into the next generation! Make sure they’re in the worst possible condition while they go off and incubate your genetic future! This is not to mention the fact that all of the energy you’ve been putting into the eggs you yourself have produced (remember, these little suckers are hermaphrodites) have now been wasted! Yippee!

This does not sound like a good thing, when one stops to think.

More likely, she points out, a lot of this is just cultural bias creeping into our observations. I mean, I’ll be honest, fast moving flatworms whipping their penises around? It sounds like some frat parties I’ve been to! Well, ok, not really – I was in a co-ed literary society, but that is neither here nor there!

The point is, you can see how easy it is to write a narrative to these behaviors that can override more dispassionate reasoning. An example may help, however.

Below are two movies of flatworm penis fencing. One, the original, is dark, gritty, with the full on sexual selection narrative as its underpinning. If you’d like, ignore the narration, and just pay attention to the underscoring of the actual mating.

Now, compare this to the same mating event, but this time underscored with “No Quiero Otro” by the Bajofondo Tango Club.

Interesting stuff. Makes you think a little bit more about the true meaning (and evolutionary costs and benefits) of Apophallation.

UPDATE: Unbeknownst to me, it’s sex week over at Deep Sea News! All of which was inspired, in part, by their amazement at the very video shown here! How perfect! Whadda ya think of penis fencing, now, guys?