Polygenicity and Play a Trophy

There is not one strong gene for how neurotic you are or how extroverted you are there are thousands of small effects. Biggest effect of a common variant on something like BMI so I'm not even personality explains like 0.4% of variation every one of those variants has a small effect and those effects are replicable. If it was one neuroscientific system like one certain type of synapse that had a strong causal role in shape of our personality we would also see snips or genes related to that system pop up energy was what we don't.