The key is that while men and women are equally web site design effective foragers, mothers carrying dependent children are not effective hunters. They must thus depend on male hunters. This favors a system in which males have exclusive sexual access to females, and females domain registration can predict that their sexual partner will provide food for them and their children. In most mammalian species the result is a system of rank or sexual competition that results in either polygyny, or life-long internet service providers pair-bonding between two individuals who live relatively independent of other adults of their species; in both cases male aggression plays an important role in maintaining sexual access to mate(s). What is unique website development about humans?