Almost all personality traits are heritable, but you can override genetic programming

• Behavioral genetics research is fairly clear that parents don’t have much of an influence on long-term personality – it is half genetics and half “non-shared environment” (which basically means things outside the home/parents)

• I generally buy The Nurture Assumption argument that non-shared environment is dominated by effects of peer category (ie if you’re a boy who likes academics, you will self-select into the ‘nerd’ category and that will self-reinforce) rather than randomness etc, though this is more based on my thoughts on how human culture is likely implemented in developing brains rather than clear scientific tests

• While it does seems like genetics is fairly determinative of longer-term personality traits, I tend to believe that it is totally possible to change your personality traits, but it’s just the case that most people simply don’t do it (for a variety of reasons). see below

From The Evolution of Culture

On the contrary, even human behaviours in whose favour there is heavy biological selection pressure, and which are immutable in animals, and which might therefore be expected to be under the tightest genetic control, are in the event all fully reversible by memes, or by individual decisions. For example, it is commonplace for human beings, either for cultural reasons or for their own private reasons, to lose the desire to eat, or to mate, or to avoid pain (e.g. in sport or sexual masochism), or indeed to survive. If such fundamental biological drives produce, in humans, only behaviours and desires that can readily be unlearned when they conflict with memes, or with the transient objectives of individuals, then what genetically determined behaviours cannot be unlearned?

It is ironic that genetic influences on behaviour, which are often assumed to be immutable and therefore responsible for the intractability of many human problems, turn out to be effectively insignificant, while certain learned behaviours, caused by anti-rational memes, though never entirely immutable, turn out to be the real cause of that intractability. But that is not surprising when we consider that anti-rational memes possess highly evolved adaptations with no other function than to cause immutable behaviour in humans, and to thwart their holders’ best efforts to think themselves free, while our genes evolved only to control the behaviour of our beast-like ancestors. Behavioural genes have had virtually no experience of human thought as an adversary. Their evolution must have ceased as soon as our capacity for reason evolved, because any selection pressure that favoured behavioural genes would almost certainly also favour anti-rational memes for the same behaviour. These could evolve thousands of times as quickly, and would be much better able to cope with subsequent changes in conditions that required further evolution. As soon as there was a meme occupying any niche, the selection pressure favouring the analogous gene would disappear. There must also be continuous selection pressure on existing behavioural genes to become more flexible, or to be dropped altogether.