Here’s what the recent Nature Neuroscience paper ‘Neurocognitive correlates of liberalism and conservatism’ (See here for one of the many news reports) made me think.
This looks like the (one of the) neural manifestation of a personality axis, such as bold/timid, extrovert/introvert. People and animals spread out all over these — reflected in animals in how quick they are to explore new environments, how far they disperse, and so on. You could probably redefine liberalism/conservatism in terms of these (people probably already have).
So the big question, I think, is: what maintains this diversity in a population? It could be frequency-dependent selection — it becomes more advantageous to be liberal if you’re surrounded by conservatives, and vice versa. Seems unlikely.
More plausible is that it’s balancing selection: there are some environments and tasks that favour a liberal approach, and some that favour conservatism. In great tits, for example, bold, far-dispersing males do better after mild winters, when territories are at a premium, and food is plentiful, whereas stay-at-homes do better after harsh winters. For females, the reverse is true.
So no one strategy can take over. And personality in these birds has a strong heritable component. So, in a variable environment, where genes don't know which sex of bird they're going to be on (unless they're on the females-only W chromosome in birds, or the male-only Y in mammals), a braod range of personality types can persist.
It seems plausible that something roughly similar might be at work in people — the benefits of reaching out, trying new stuff, versus the benefits of staying put and consolidating will depend on the environment. Question here is, why can’t each of us (or each great tit, for that matter) work that out, and adapt to any environment? What is it about our brains, and the genes (and environments) that make them constrains us to occupy our place on the personality axis?
It seems, anyway, that if our politics come from inside us, as well as being a consequence of what the world does to us, we can’t expect political extinction for either liberals or conservatives, just as there are bold and timid great tits.
Of course, when it comes to voting, there’s lots of other stuff at work. It struck me that this is a US study, where, because the different parties don’t offer anything different in the way of economics, peoples’ voting decisions may be more swayed by all that ‘values’ stuff that tickles these particular ‘am I up for this?’ bits of the brain. Also I’m guessing that those studied were students, and occupied a narrow socioeconomic band. It’s perfectly possible to be a left-wing conservative, but more likely if you’re working class, I’d guess.