Sir

Trend extrapolation can be an inexact science, especially in sport. A. J. Tatem and colleagues (Nature 431, 525; 200410.1038/431525a) suggest, counterintuitively, that a future woman may run faster than her male counterpart over 100 metres. It is worth noting that the ‘fastest human on the planet’ is usually the world-record holder for the 200 m, not the 100 m. For example, Michael Johnson's running velocity for his current world record 200 m in 19.32 s was 10.35 m s−1, whereas Tim Montgomery's for his 100 m in 9.78 s was 10.22 m s−1.

However, sports physiologist Stephen Seiler has analysed Olympic and world championship running results and found that the mean performance gender gap in the world records has actually increased from 10.4% in 1989 to 11.0% now (C. Holden Science 305, 639–640; 2004). This held for seven of the eight events from 100 m upwards. The exception was Paula Radcliffe's marathon, which narrowed the gap from a relatively vulnerable 11.9% to 8.4%. Hence, in general, the gap has widened during the past 20 years.

Nevertheless, Tatem and colleagues make the very good point that only a minority of the world's population of women has been able to compete. Were China and India, with their vast populations, to come fully onstream in track and field sports, they could bring with them statistical outliers of both sexes who would demolish current records. But it is likely that there would still be a gender gap in the range of 7–10% in favour of the biologically advantaged men.