The fact that dirt and contamination were threats to our ancestors suggests:

It may help with awareness or obsessive - compulsive disorder

Explanation:

answer; researchers typically cannot control people's sexual behaviors as would be necessary in an experiment;

    racial conflict and discrimination has existed ever since man learned to kill with rocks and bones. these conflicts arose from disputes between territory, power, wealth, religion, or simple difference. some of the most infamous racial disputes include slavery, the holocaust, and the civil rights movement.

    these listed disputes often resulted in casualties from all sides. riots, wars, imprisonment, and lynching are all commonly associated with racial conflict on severe levels.

      however, racism is an improving issue in recent decades. people are being more accepting and welcoming of diverse populations. though, the world isn't perfect and it will take much more time, if ever, until the world is rid of racism.