These groups are what socialize all of us during development. Adults create their own groups, and they influence each other s parenting methods. Studies show that women from same social class, ethnic group, or neighborhood are more similar to each other in child-rearing methods than they are to their parents. That will make it seem as if the parents are having a strong influence on the children. Child behaves in ways to be accepted.
Children create intense between-group contrasts.
For example, sex-based segregation happens despite parents best intentions. Kung farmers, sex-based segregation much more common. In general, when girls and boys together, girls become more girl-like. Girls played dodgeball, and played competitively and even aggressively, and they were skillful. When boys introduced into the same game as competitors, girls changed behavior.