It’s 200 years since Darwin was born, 150 years since the publication of the Origin, and 30 years since I started out on a PhD course studying barnacles. I’ve never directly used my barnacle research in my later career(s), but I often feel that those four years studying sex and violence in barnacles formed the foundation of my way of thinking and writing. I have used the barnacle knowledge very little, but I have used my training as a scientist a lot. Darwin spent twice as long studying barnacles, and said that was too long; but I don’t think he meant it. He embarked on his study in order to become an expert in a group of species, so he could get a real feel for how living things are similar to each other- a real foundation for his main work on evolution. I suppose he also needed to be seen as an expert on something before he’d be taken seriously when he published his Origin of Species bombshell.
Anyway, in that happy hour of lucid half sleep I often spend before the alarm goes off, mindful of all these anniversaries this year, I thought about Darwin’s wedges:
The face of Nature may be compared to a yielding surface, with ten thousand sharp wedges packed close together and driven inwards by incessant blows, sometimes one wedge being struck, and then another with greater force.
Darwin uses this metaphor to illustrate the struggle for existence- an excess of possible inhabitants of any space competing with each other for existance. It’s a setup for the central observation that the fittest survive, the weaker die: the best wedge or the one driven in most powerfully stays there; the weaker wedge drops out. The metaphor was humorously invoked in the animated film Ice Age (which abounded in evolution in-jokes) in which the character Scrat, a squirrel -like creature, attempted to jam as many acorns as possible into a hollow tree trunk.
Anyway, much of my research was in how barnacles live- something Darwin didn’t pay too much attention to- he was mainly into taxonomy, describing species and looking at how they were related. When barnacle larvae settle on rock , there are far too many for the available space. You can see from this photo that this year’s larval settlement on the bare rock number far more than the adults in an equivalent area. It turns out that competition for space is done in an actual physical way. The larvae grow until they cover all the available space, after which they jostle and squash each other. Any barnacle which distorts so much that it can’t extend its legs out of the hole at the top of its shell properly to feed dies either because it’s physically squashed or starves to death.
In thirty years, I’d treated Darwin my predecessor in barnacle research almost as a different person to Darwin the discoverer of natural selection. Only today did I realise that I had spent 4 years studying probably one of the few actual, living examples of animals acting out Darwin’s inanimate metaphor. As far as I can tell from a quick Google, nobody else seems to have noted this remarkable link between the two great areas of Darwin’s research- the crowding and physical competition for living space acted out by the billions of natural wedges that are the barnacles of his 8 year study, illustrating in real time every day one of the most memorable metaphors in his ‘most beautiful and most wonderful’ book.
Adult barnacles with larval settlement
