I agree, mostly, but
And the authors' conclusion is therefore moot - if what is considered 'liberal' changes over time and the ideological distribution is relational only, then the gene expression that may predispose to an ideology that is considered liberal now may have predisposed to an entirely different ideology in the past and a further different one in the future.
This is making the assumption that the gene is pushing individuals towards an ideology based on content.
I'd argue content is irrelevant. In my hypothesis it simply pushes the individual towards an ideological position on the spectrum. In 1100 the far-left position may be that women should be allowed to speak in public and there is no need to kill the foreigners' babies as well as their adults. In 2010 it may be what we consider 'liberal' today. The traits at work simply tend to cause someone to fork left more than they fork right; the actual definitions of 'left' and 'right' in the society they live in are comparatively immaterial, so long as they're correlated with introversion vs. extroversion, acceptance vs. defensiveness, whatever.
This will break down in scenarios where the political range is extremely compressed, for example a very successful totalitarian state in which the spectrum only goes from 'state approved far right' to 'subversive discontent but still far right.'
