A high proportion of human societies have chosen some form of gender segregation and it is one of the biggest criticisms westerners often level at non-western societies. In recent years there is evidence that western civilisation may be adopting increased gender segregation.
A lot of gender segregation in western countries is being driven by women who state that they often feel threatened by men, sometimes merely by their presence. Women have formed many women-only organisations in western countries (eg, gyms). This raises the interesting question about whether it was women who drove segregation in other societies. This would be interesting considering that gender segregation in non-western countries today is often claimed as principally disadvantaging women.
It may be reasonable for a society to permit gender segregation, but it must be on just and equal terms. Thus a society should permit both men-only and women-only organisations only if they are available on equal terms. A society should allow both or it should allow neither. Currently women in the west enjoy women-only organisations while men are prohibited from having men-only organisations.