Notes of the Quarter

¨ Alexander Lerchl, of the University of Münster, has found that more boys are conceived shortly after heat waves. He examined birth records from Germany between 1945 and 1995, and found that more boys were born between April and June, and fewer in October. Dr Lerchl suggests that the temperature may have effects on the maturing sperm. He speculates that sperm carrying the X-chromosome may be more easily damaged than those with the Y-chromosome, leading to a greater number of boys.