The Better Half: On the Genetic Superiority of Women review – bold study of chromosomal advantage

Sharon Moalem offers an intriguing theory on how two X chromosomes give women the edge in everything from colour vision to coronavirus

It was noticeable from the initial outbreak in Wuhan that Covid-19 was killing more men than women. By February, data from China, which involved 44,672 confirmed cases of the respiratory disease, revealed the death rate for men was 2.8%, compared to 1.7% among women. For past respiratory epidemics, including Sars, Mers and the 1918 Spanish flu, men were also at significantly greater risk. But why?

Much of the reason for the Covid-19 disparity was put down to men's riskier behaviours - around half of Chinese men are smokers, compared with just 3% of women, for instance. But as the coronavirus has spread globally, it's proved deadlier to men everywhere that data exists (the UK and US notably - and questionably - do not collect sex-disaggregated data). Italy, for instance, has had a case fatality rate of 10.6% for men, versus 6% for women, whereas the sex disparity for smoking (now a known risk factor) is smaller there than China - 28% of men and 19% of women smoke. In Spain, twice as many men as women have died. Smoking, then, is unlikely to account for all of the sex disparity in Covid-19 deaths.