Africa had used slavery long before the New World, tribes would enslave each other. hope this helps :)
Was a cause because building an empire needs manpower such as an army and a navy to conquer and keep the land that they colonised. The alliances system meant that a local conflict could easily result into an intimidating global one.
The women's movement was on a roll. They got the right to vote, and many more social recognition's, but were still slightly discriminated against. The "Flappers" were drawn to speakeasy in an effort to break the assumed differences between genders. If men could do it, so could they. Also, in a period of change and "all about me" and breaking away from traditions. Drinking was considered highly unladylike and unproper. Especially since it was illegal.