The Neolithic era began circa 10,000 BC; this period saw a number of important changes, such as the introduction of pottery (as evidenced at Tagalagal, Temet and Tin Ouffadene), the spread of cattle husbandry, and the burying of the dead in stone tumuli. As the climate changed in the period 4000–2800 BC the Sahara gradually began drying out, forcing a change in settlement patterns to the south and east. Agriculture became widespread, notably the planting of millet and sorghum, as well as pottery production. Iron and copper items first appear in this era, with early find including those at Azawagh, Takedda, Marendet and the Termit Massif. The Kiffian (circa 8000–6000 BC) and later Tenerian (circa 5000–2500 BC) cultures, centred on Adrar Bous and Gobero where numerous skeletons have been uncovered, flourished during this period.