Eight days ago scientists at the University of California announced that they had found a gene for liberalism. People with the dopamine receptor gene DRD4 were already known to exhibit more "novelty-seeking behaviour" than those without it. Now it appeared that they were more likely to develop liberal political opinions, too, provided they enjoyed an active social life in their teens. A desire for novel experience, so the theory goes, leads the young to seek out and understand people with different backgrounds, which in turn leads to greater tolerance in later life. "It is the crucial interaction of two factors - the genetic predisposition and the environmental condition of having many friends in adolescence - that is associated with being more liberal," said the researchers.
It's a strange thought. Odder, however, is the fact that no outcry has yet greeted it, though it could have been formulated precisely to nettle an earlier generation of liberal. After all, few topics in science have caused as much political acrimony as the question of how our genes shape our minds.
The battlelines used to be quite clear. The left has traditionally preferred nurture-led accounts of human variation, for the reason that if important aspects of our personality - our IQs, for instance - are innate, this could lead to scepticism about how much equality is possible (or desirable). It might also encourage racism and sexism, since different ethnic groups average different scores on psychometric tests, as do men and women.
At their worst, left-aligned commentators have been quick to accuse scientists of bigotry simply because their work addresses these issues. When Arthur Jensen published a quite tentative paper titled How Much Can We Boost IQ and Scholastic Achievement? in 1969, students and faculty at Berkeley staged protests outside his office. The article was one of the most cited in the field but Jensen's publisher refused to reprint it or issue his replies to critics. Jensen had been branded a racist and that was that.
Such reactions are, of course, deplorably unscientific. On the other hand, there has been so much shoddy work in support of the hereditarian position that suspicion is justified. The annals of behavioural genetics are a litany of invented data, mental evaluations so cursory they barely merit the name, and a persistent failure to use adequate statistical tools. As late as 2006, the psychologist Denny Borsboom lamented in the journal Psychometrika that "contemporary test analysis bears an uncanny resemblance to the psychometric state of the art as it existed in the 1950s."
Against this unhappy history, the idea that liberal political convictions are themselves quirks of genetics might be taken for a deliberate provocation. Yet no one has risen to it. Why? Perhaps liberals are flattered by the implication that they were popular as teenagers. Alternatively, it may be that the hereditarian hypothesis is now widely accepted, even on the left. As the psychologist Eric Turkheimer wrote in 2000: "The nature-nurture debate is over. The bottom line is that everything is heritable." And it is true that mounting evidence, for instance from separated identical twins, points to a strong role for nature in the formation of character.
What isn't established, however, is the irrelevance of nurture. Intelligence is a highly heritable psychological trait. Even so, since 1977 it has been known that the average IQ in industrialised countries is increasing at a speed that is hard to account for genetically. The rankings between demographics may remain stable but a rising tide lifts all ships. This is known as the Flynn effect and changes in culture seem the most likely explanation for it. Yet if intelligence can be altered in this way, mightn't other traits -political allegiance, for example - be similarly malleable? If so, the prospects for equality might not be as bleak as some genetic determinists allege. In light of last month's discovery, it would be ironic indeed if this glimmer of hope were to win any converts to the liberal faction.