What are the main causes of gender discrimination ?

The history of discrimination against women goes back ages. In the early time when hunting and gathering were the only source of living, women mostly kept indoors to fulfill the need of progeny. Giving birth to a child and increasing human race was then very important as the existence of the race was still unsure. It is from here that the tradition of keeping women indoors and labelling them as unfit for any other job starts. With the emergence of modern age the fear of the human  race coming to an end is over. This means that there is no need for women to stay back. However, the age old dogma seems to have ridden the society and this makes it difficult for women to come out and establish her self.