RT Journal Article SR Electronic T1 Adaptive reasons for variation in sex ratios JF Canadian Medical Association Journal JO CMAJ FD Canadian Medical Association SP 1715 OP 1715 DO 10.1503/cmaj.112-2070 VO 184 IS 15 A1 João Alpedrinha A1 Geoff Wild YR 2012 UL http://www.cmaj.ca/content/184/15/1715.1.abstract