Shrek II, from an Evolutionary PerspectivePublished 25 October, 2010
In Shrek II, Princess Fiona and Shrek visit Fiona’s parents in the land of Far Far Away – which in certain respects bears an unusual resemblance to Beverly Hills – where conflict – and hilarity! – erupts over the issue of Fiona’s mate choice and, related, the succession to the throne. Had Fiona married Prince Charming, as her parents originally intended, the throne would have passed to this happy couple, and their offspring would have been, presumably, more or less human. But because Fiona married Shrek the Ogre rather than Prince Charming, both offspring and succession are put in doubt.
From an evolutionary perspective, it is very easy to see why parents should be concerned about their offspring mating with a member of a different species. Given the likelihood of the production of viable offspring – usually low, but the magical setting of Shrek makes this unclear – their fitness interests are harmed by this choice.
Of course, from an evolutionary perspective, Fiona’s fitness interests are also harmed by mating with a member of a different species. So, under normal conditions, parents and children should be equally unfavorably disposed toward an interspecies match. In some ways, this makes all of the conflict between parents and offspring puzzling, since they both win and lose with the same mate choices.
But parents and children don’t always have identical interests. A paper by Shelli Dubbs and Abraham Buunk just published in Evolutionary Psychology makes (roughly) the following argument. Suppose Fiona’s parents have other offspring. Suppose further that by marrying Shrek rather than Charming, Fiona is getting good (ogre) genes, but losing out in terms of investment. Charming, after all, seems to be well connected and well off; he is, well, Charming. In contrast, Shrek, holding aside a talking donkey, is basically friendless. Shrek, then, might be good for Fiona – she gets the sexy ogre – but less good for Fiona’s parents’ other offspring in the following sense. As Dubs and Buunk put it, certain mate choices “can lead to the child needing extra support from its parents in order to sustain themselves and the child’s offspring. Relying on the parents for support is, of course, much more costly to the parents than it is for the child. Parents, who would ideally like to distribute their resources evenly to all offspring, would see this as detrimental to their other children and grandchildren.”
They’re saying that if Fiona mates with Shrek, Fiona’s parents lose Charming’s resources, and so their other offspring are worse off than they would otherwise be.
In their work, drawing on participants from the mundane, real world, they show that children like traits that go with good genes, but parents prefer traits that connote potential investment. Fiona wants the sexy ogre, but King Harold would prefer she marry the sensible (if somewhat insufferable) Prince Charming.