When did early Iron Age farmers begin using iron tools in the Botswana region?

The earliest evidence of Iron Age activity in Botswana dates to approximately 190 ce. This is based on the discovery of an iron-smelting furnace located in the Tswapong Hills near Palapye, which is believed to be associated with farmers arriving from the Limpopo valley.12

While Bantu-speaking farmers were utilizing iron tools on the upper Zambezi as early as 20 bce, the archaeological record indicates that these practices reached the Botswana region later. Subsequent evidence of early Iron Age farming settlements includes remains near Molepolole dated to about 420 ce and sites in the Tsodilo Hills dated to approximately 550 ce.12