<P> The Darb el - Arbain trade route, passing through Kharga in the south and Asyut in the north, was used from as early as the Old Kingdom for the transport and trade of gold, ivory, spices, wheat, animals and plants . Later, Ancient Romans would protect the route by lining it with varied forts and small outposts, some guarding large settlements complete with cultivation . Described by Herodotus as a road "traversed...in forty days", it became by his time an important land route facilitating trade between Nubia and Egypt, and subsequently became known as the Forty Days Road . From Kobbei, 40 kilometres (25 mi) north of al - Fashir, the route passed through the desert to Bir Natrum, another oasis and salt mine, to Wadi Howar before proceeding to Egypt . The Darb el - Arbain trade route was the easternmost of the central routes . </P> <P> The westernmost of the three central routes was the Ghadames Road, which ran from the Niger River at Gao north to Ghat and Ghadames before terminating at Tripoli . Next was the easiest of the three routes: the Garamantean Road, named after the former rulers of the land it passed through and also called the Bilma Trail . The Garamantean Road passed south of the desert near Murzuk before turning north to pass between the Alhaggar and Tibesti Mountains before reaching the oasis at Kawar . From Kawar, caravans would pass over the great sand dunes of Bilma, where rock salt was mined in great quantities for trade, before reaching the savanna north of Lake Chad . This was the shortest of the routes, and the primary exchanges were slaves and ivory from the south for salt . </P> <P> The western routes were the Walata Road, from the Sénégal River, and the Taghaza Trail, from the Mali River, which had their northern termini at the great trading center of Sijilmasa, situated in Morocco just north of the desert . The growth of the city of Aoudaghost, founded in the 5th century BCE, was stimulated by its position at the southern end of a trans Saharan trade route . </P> <P> To the east, three ancient routes connected the south to the Mediterranean . The herdsmen of the Fezzan of Libya, known as the Garamantes, controlled these routes as early as 1500 BC . From their capital of Germa in the Wadi Ajal, the Garamantean Empire raided north to the sea and south into the Sahel . By the 4th century BC, the independent city - states of Phoenecia had expanded their control to the territory and routes once held by the Garamantes . Shillington states that existing contact with the Mediterranean received added incentive with the growth of the port city of Carthage . Founded c. 800 BCE, Carthage became one terminus for West African gold, ivory, and slaves . West Africa received salt, cloth, beads, and metal goods . Shillington proceeds to identify this trade route as the source for West African iron smelting . Trade continued into Roman times . Although there are Classical references to direct travel from the Mediterranean to West Africa (Daniels, p. 22f), most of this trade was conducted through middlemen, inhabiting the area and aware of passages through the drying lands . The Legio III Augusta subsequently secured these routes on behalf of Rome by the 1st century AD, safeguarding the southern border of the empire for two and half centuries . </P>

How did the sahara desert affect the development of africa