it seems that pessimism genes might quite literally be commoner than optimism genes: only about 20 per cent of people are homozygous for the long version of the serotonin transporter gene, which possibly endows them with a genetic tendency to look on the bright side. (Willingness to take risks, a possible correlate of optimism, is also partly heritable: the 7-repeat version of the DRD4 gene accounts for 20 per cent of financial risk taking in men – and is commoner in countries where most people are descended from immigrants.)
