This post is part of a series on The Origin Of Species. It was originally posted on the old blog in feb 2009, during the Darwin 200 celebrations.
In chapter eight, Darwin looks at instincts. Instincts are subject to the same processes of variation and heredity as everything else in life, so obviously they are subject to evolution. Rather than catalogue lots of examples of instincts as adaptations, Darwin focuses on three case studies which represent especially complicated or problematic instincts, but which Darwin sets out to show are clear examples of adaptation by natural selection. These are the cuckoo’s exploitation other birds in the fostering of young; the honey-bee’s skills in constructing perfect wax cells; and the complex habits of ants, particularly their symbiotic relationships with other species.
When it comes to instinct and behaviour, it’s difficult to keep one’s communications clear, concise, and objective: it’s almost impossible to avoid connotations of purpose, forethought, and consciousness in the language that we use to describe animal instincts and their evolution. Darwin is soft on and forgiving of the cuckoo: the poor dear can’t help being a parasite on bird society, she has to dump her kids on other birds because she’s just popping them out all over the place, and could never take care of them all herself. And, sure the offspring, before they can even open their eyes, push their foster siblings out of their foster nest, in order to get the undivided attention of their poor foster parents. But what you don’t realise is that this is a beneficent arrangement, because the cuckoo is kind enough to butcher his foster brothers and foster sisters while they’re still young to suffer greatly while they die.
But Mr Darwin is no softie on ants. The accepted terminology for the sort of relationship where one species of ant exploits the labour of another species of ant in the nest was that this is a “master” and “slave” relationship. Darwin does his best to make a disinterested study into the ants’ “remarkable” instincts, but can not help passing a few judgements. After some big ants get into a fight with some little ants, the “tyrants” run off with the little ants’ pupae. Meanwhile some masters go on expeditions to “ravage” the homes of other ants, searching for potential slaves. And the poor slave species run around in “despair”. I don’t believe the claims that Darwin was motivated in his work by his hatred of slavery. His motivation, I would hope, was to seek the truth. But I think he let his political leanings show in the half-hidden asides.