Green Sahara in the context of "Cave of Swimmers"

Trans-Saharan trade is trade between sub-Saharan Africa and North Africa that requires travel across the Sahara. Though this trade began in prehistoric times, the peak of trade extended from the 8th century until the early 17th century CE. The Sahara once had a different climate and environment. In Libya and Algeria, from at least 7000 BCE, pastoralism (the herding of sheep and goats), large settlements and pottery were present. Cattle were introduced to the Central Sahara (Ahaggar) between 4000 and 3500 BCE. Remarkable rock paintings (dated 3500 to 2500 BCE) in arid regions portray flora and fauna that are not present in the modern desert.

As a desert, the Sahara is now a hostile expanse that separates the Mediterranean economy from the economy of the Niger River Basin. As Fernand Braudel points out, crossing such a zone, especially without mechanized transport, is worthwhile only when exceptional circumstances cause the expected gain to outweigh the cost and the danger. Trade was conducted by caravans of camels. According to Maghrebi explorer Ibn Battuta, who once traveled with a caravan, an average one would amount to 1,000 camels, but some caravans were as large as 12,000. The caravans were guided by highly-paid Berbers, who knew the desert and could ensure protection from fellow desert nomads. The caravans' survival relied on careful coordination: runners would be sent ahead to oases for water to be shipped out to the caravan when it was still several days away, as the caravans could usually not carry enough to make the full journey. In the mid-14th century CE, Ibn Battuta crossed the desert from Sijilmasa via the salt mines at Taghaza to the oasis of Oualata. A guide was sent ahead, and water was brought over a four-day journey from Oualata to meet the caravan.

The Pastoral Neolithic (5000 BP - 1200 BP) refers to a period in Africa's prehistory, specifically Tanzania and Kenya, marking the beginning of food production, livestock domestication, and pottery use in the region following the Later Stone Age. The exact dates of this time period remain inexact, but early Pastoral Neolithic sites support the beginning of herding by 5000 BP. In contrast to the Neolithic in other parts of the world, which saw the development of farming societies, the first form of African food production was nomadic pastoralism, or ways of life centered on the herding and management of livestock. The shift from hunting to food production relied on livestock that had been domesticated outside of East Africa, especially North Africa. This period marks the emergence of the forms of pastoralism that are still present. The reliance on livestock herding marks the deviation from hunting-gathering but precedes major agricultural development. The exact movement tendencies of Neolithic pastoralists are not completely understood.

The term "Pastoral Neolithic" is used most often by archaeologists to describe early pastoralist periods in eastern Africa (also known as the "East African Neolithic"). In the Sahara, hunter-gatherers first adopted livestock (e.g., cattle, sheep, goats) in the eighth to seventh millennia BP. As the grasslands of the Green Sahara began drying out in the mid-Holocene, herders then spread into the Nile Valley and eastern Africa.

North African climate cycles have a unique history that can be traced back millions of years. The cyclic climate pattern of the Sahara is characterized by significant shifts in the strength of the North African Monsoon. When the North African Monsoon is at its strongest, annual precipitation and consequently vegetation in the Sahara region increase, resulting in conditions commonly referred to as the "green Sahara". For a relatively weak North African Monsoon, the opposite is true, with decreased annual precipitation and less vegetation resulting in a phase of the Sahara climate cycle known as the "desert Sahara".

Variations in the climate of the Sahara region can, at the simplest level, be attributed to the changes in insolation because of slow shifts in Earth's orbital parameters. The parameters include the precession of the equinoxes, obliquity, and eccentricity as put forth by the Milankovitch theory. The precession of the equinoxes is regarded as the most important orbital parameter in the formation of the "green Sahara" and "desert Sahara" cycle.