The major theory on the origin of patriarchy mixes biological and societal factors to explain how patriarchy came about.
The origins of patriarchy begin with biology. To state the obvious, it is women who become pregnant and bear children. It is women who nurse young children until they are old enough to eat solid food. Therefore, in the past, it was women who would stay near to home. Women would take care of work around the home while men went out to do things like hunting. It was men who would therefore come into contact with other groups of people. It was men who would trade with them. Biological differences, it is believed, caused a division of labor between the sexes.
This division of labor came to have an impact on ascribed status. In other words, men came to define what they were doing as more important than what women were doing. In other words, men took a fact of life (the role of women in reproduction and its consequences for the division of labor) and socially constructed a greater meaning for it. They took these differences in the work they did and they were able to define their own role as the more important.
Different scholars place different amounts of weight on the biological and the social aspects of this origin. However, the general idea that both have played a role in the creation of patriarchy can be seen as the major theory on the origin of patriarchy.