The fact that more girls than boys are born worldwide is one that’s baffled researchers for more than a century. But a new study finds that proximity to the equator narrows the gap. Using a decade of data on sex ratio at birth and annual variations in day length and temperature, along with the latitude of 202 capital cities, Kristen J. Navara of the University of Georgia found that European and Asian countries had the highest sex ratios (51.4 per cent boys), which African countries had the lowest sex ratios with 50.7 percent boys.