It certainly proves that gender identity and perceived gender roles are not entirely environmental. If the segregation of of boy toys and girl toys were the only or primary cause of gender personality for boys and girls then it would have been easy to raise Reimer as a girl. As it is, this demonstrates that at least a substantial portion of femininity for girls and masculinity for guys is inborn. That not every girl is feminine and not every guy is masculine, despite upbringing, actually reinforces this point.