The evolutionary theory of gender suggests that aspects of our behaviour have been biologically coded and adapted to ensure our survival. This explains the gender roles. Human ancestors over 10,000 years ago had to adapt their minds to their hunter-gatherer surroundings. The gender roles are therefore evolutionary adaptations which are biological to ensure that the species survives.
The hunters (males) needed strength, agility, competitiveness, and aggression to attain this, and the gatherers (females) were developed to nurture, grow food, provide shelter, and look after the offspring. The female was not encouraged to hunt as this would have discouraged reproduction and the production of milk. Biological evolution is therefore the root of the gender role differences which has been present through human evolution irrespective of culture.