Cultural variation in the main finding.

<p>Panel (a): the ratio between same-gender and mixed gender pictures of different group size (corrected by the probability of appearance, see text). Panel (b): number of close friends (same gender, with groups size 2 to 4). Panel (c): the ratio between same-gender Profile Pictures as a function of group size (1F/1M normalised to 0). Panel (d): cultural variation in the proportion of single person pictures within all Profile Pictures in a given global region. (Region codes of Panels a-c: green: Central and South Asia, blue: Europe, dashed blue: Latin America, dashed green: Middle East and North Africa, dotted blue: North America, dotted green: South-East Asia, red: Sub-Saharan Africa, black: Australia, dashed black: East Asia.)