Q. Why do girls seem to skip more than boys?
A. "Boys and girls are somewhat different even at birth, but I don't think little girls are born to skip. Most likely, girls skip because they see other girls doing it, and boys don't skip because they don't see other boys doing it. By the age of 3, girls identify themselves as "girls" and take their cues on how to behave from other girls they see - in particular, those slightly older than themselves.
”By the age of 3, girls identify themselves as 'girls' and take their cues on how to behave from other girls they see, in particular slightly older girls
Judith Rich Harris, Child development psychologist, US [from New Scientist]
In other words, what you might otherwise read as something inherent to a group is established through iterative interactions with peers...and copying