How did the Europeans conquer and enslave the Africans, not the other way around?Can be found in Chapter 19, "How Africa Became Black"

The Europeans "won" because they had guns and technology,
literacy, and "better" political organization.  Diamond says this on p. 398 in my book. 
But those are proximate causes.  Diamond also says there are more basic reasons why
Europeans had these advantages.

1. Europeans had
   more animals that could be domesticated.  Most African animals can't be
   tamed.


2. Europeans had more plants that could be
   domesticated.  Between these two factors, Europe was able to have more agriculture
   sooner.


3. Africa has much less area than Eurasia -- this
   means Eurasia could have more societies and faster
   development.


4. Africa has a long north-south axis with lots
   of different climates.  This makes it hard for crops and such to spread through the
   continent.