The mbira appears to have been invented twice in Africa: a wood or bamboo-tined instrument appeared on the west coast of Africa about 3000 years ago, and metal-tined lamellophones appeared in the Zambezi River valley around 1,300 years ago.[3] These metal-tined instruments traveled all across the continent and differentiated in their physical form and social uses as they spread. Kalimba-like instruments came to exist from the northern reaches of North Africa to the southern extent of the Kalahari Desert, and from the east coast to the west coast, though many or most groups of people in Africa did not possess mbiras. There were thousands of different tunings, different note layouts, and different instrument designs, but there is a hypothetical tuning and note layout of the original metal-tined instrument from 1,300 years ago.[citation needed]