Africa was the location of some of the earliest evidence of human evolution, as evidenced by the fossils of early hominids. Owing to a lack of written records, however, it can be difficult to study the cultures of that time. The earliest peoples were individual huntergatherer groups that developed into more sedentary agriculturalists during the Neolithic Period (ca. 8800–4700 BCE) with the introduction of wheat and barley cultivation beginning in Egypt and expanding into Nubia during the fifth and fourth millennia BCE. These crops enabled people to establish small communities, which eventually developed into unified societies evolving into the earliest civilizations in Africa. Three such civilizations formed in Egypt, Nubia, and Carthage.