Moroccans descended from Berbers, Arabs, and Black Africans exactly like the neighboring Maghrebians. The Berbers are the prehistoric populations of Morocco and are related to the wider group of Paleo-Mediterranean peoples. The Afroasiatic family may have originated in the Mesolithic period, perhaps in the context of the Capsian culture.
Epidemiologic triangle model of disease causation. A common model used in public health illustrates the relationships among an agent, a host and the environment. It applies to biological, chemical and physical agents.
All findings must relate to a defined population. A key feature of epidemiology is the measurement of disease outcomes in relation to a population at risk. The population at risk is the group of people, healthy or sick, who would be counted as cases if they had the disease being studied.