Guns, Germs and Steel
Humans also domesticated animals. As with plants, only some animals were good for this. For example, animals that lived in herds were easier to control than animals that lived alone. Mostly for similar reasons, Eurasia had more farm animals than the other parts of the world. Only two large animals were domesticated outside of Eurasia: llamas and alpacas in South America. Living with animals caused humans to catch more diseases. These spread through Eurasia and Africa. This is why many Native Americans died of diseases after European people travelled to the Americas, but the Europeans did not catch diseases from the Native Americans. On the other hand, in tropical areas, diseases like malaria stopped Europeans from moving into those areas until the late 19th century.