6000–3000 BCE: (The Age of Agricultural Exchange — A New Global Period Beginning from Around the Middle of the Holocene as Expanding Early Agricultural Syste…

6000–3000 BCE: (The Age of Agricultural Exchange — A New Global Period Beginning from Around the Middle of the Holocene as Expanding Early Agricultural Systems Increasingly Came into Contact with Each Other and Crops and Animals Began to Be Adopted from One System into Another, the Earliest Notable Exchange Being the Diffusion of Sheep and Goats from the Levant Southward to Cushitic and Nilo-Saharan-Speaking Peoples of the Eastern Sahara Beginning Shortly Before 6000 BCE): From around the middle of the Holocene, an emerging age of agricultural exchange began to take shape, as the expanding early agricultural systems increasingly came into contact with each other, and crops and animals began to be adopted from one system into another. In the global frame, agricultural exchange did not have a closely datable beginning or end, despite the notional dating of 6000–3000 BCE. The earliest notable exchange was the diffusion of sheep and goats, coming from the Levant southward to Cushitic and Nilo-Saharan-speaking peoples of the eastern Sahara, which began shortly before 6000 BCE. The age of agricultural exchange marks a new phase in human history — the moment when the independently invented agricultural systems of the world began to interact, to borrow from each other, to hybridize. The thirteen independent centers of agricultural invention had each developed their own crop complexes and their own animal domesticates. Now those complexes began to meet, and the result was a global process of agricultural enrichment in which each system became more productive by incorporating elements from the others. The Nilo-Saharan cattle herders of the eastern Sahara adopted sheep and goats from the Levant, adding new animals to a pastoral economy that already included African-domesticated cattle. The exchange was not one-directional. It was reciprocal — and in the opposite direction, Africa’s contributions to Eurasia would prove equally transformative.