Prehistoric Egypt and Predynastic Egypt span the period from the earliest human settlement to the beginning of the Early Dynastic Period around 3100 BC, starting with the first Pharaoh, Narmer for some Egyptologists, Hor-Aha for others, with the name Menes also possibly used for one of these kings. At the end of prehistory, "Predynastic Egypt" is traditionally defined as the period from the final part of the Neolithic period beginning c. 6000 BC to the end of the Naqada III period c. 3000 BC. The dates of the Predynastic period were first defined before widespread archaeological excavation of Egypt took place, and recent finds indicating very gradual Predynastic development have led to controversy over when exactly the Predynastic period ended. Thus, various terms such as "Protodynastic period", "Zero Dynasty" or "Dynasty 0" are used to name the part of the period which might be characterized as Predynastic by some and Early Dynastic by others. The Predynastic period is generally divided into cultural eras, each named after the place where a certain type of Egyptian settlement was first discovered. However, the same gradual development that characterizes the Protodynastic period is present throughout the entire Predynastic period, and individual "cultures" must not be interpreted as separate entities but as largely subjective divisions used to facilitate study of the entire period. The vast majority of Predynastic archaeological finds have been in Upper Egypt, because the silt of the Nile River was more heavily deposited at the Delta region, completely burying most Delta sites long before modern times. Paleolithic Excavation of the Nile has exposed early stone tools from the last million or so years. The earliest of these lithic industries were located within a 30-metre (100 ft) terrace, and were primitive Acheulean, Abbevillian (Chellean) ( 600,000 years ago), and an Egyptian form of the Clactonian ( 400,000 years ago). Within the 15-metre (50 ft) terrace was developed Acheulean. Originally reported as early Mousterian ( 160,000 years ago) but since changed to Levalloisean, other implements were located in the 10-metre (30 ft) terrace. The 4.5- and 3-metre (15–10 ft) terraces saw a more developed version of the Levalloisean, also initially reported as an Egyptian version of Mousterian. An Egyptian version of the Aterian technology was also located. Wadi Halfa Some of the oldest known structures were discovered in Egypt by archaeologist Waldemar Chmielewski along the southern border near Wadi Halfa, Sudan in Arkin 8