Richard Lynn and Davide Piffer (2011)
http://www.pontecorboli.com/ejournals/ija/2011-AIJA12.pdf#page=78 (p 78-87 / 75-84)
Sex differences in foreign language ability are presented for a number of countries. Females consistently achieve better average results than males on foreign language ability in all the countries, and the superiority of girls in foreign languages was generally greater than in their own native language. Females perform better than males in public examinations in foreign languages, and more females than males choose to study foreign languages at school and college. An explanation for the superiority of females in foreign language ability is proposed in terms of evolutionary psychology and anthropology to the effect that females typically moved into neighboring groups in the evolutionary environment, and this gave a selective advantage to females who could acquire a foreign language easily.