Because disease are air-borne and as we know, Africa is closer to Europe than is the Americas. So as these diseases were transmitted through air, civilizations in Africa most likely built immunities to these diseases. However, as the Americas were so far away, civilizations in the Americas were unable to build immunities as they were never exposed to such diseases. Also, while the Americas weren't exposed to much zoonotic diseases as we didn't use domesticated animals till the Europeans arrived, from what I know, I believe Africa did. And much of the diseases from Europe that affected the Americas were zoonotic diseases.
GDP, or economic growth. This is a measure of all the goods and services produced in a country over a period of time, for example, a year. An increase means the economy growing.
The angles of impact and the point of convergence can tell us the way the weapon was used to commit the murder. The processes and equipment are through laser and simple trigonometry in order to get to the right angles of the impacts and the area in which the victim was killed.
