Date Published: May 8, 2019
Publisher: Public Library of Science
Author(s): Neus Isern, Joaquim Fort, Andrew Baggaley.
The subsistence of Neolithic populations is based on agriculture, whereas that of previous populations was based on hunting and gathering. Neolithic spreads due to dispersal of populations are called demic, and those due to the incorporation of hunter-gatherers are called cultural. It is well-known that, after agriculture appeared in West Africa, it spread across most of subequatorial Africa. It has been proposed that this spread took place alongside with that of Bantu languages. In eastern and southeastern Africa, it is also linked to the Early Iron Age. From the beginning of the last millennium BC, cereal agriculture spread rapidly from the Great Lakes area eastwards to the East African coast, and southwards to northeastern South Africa. Here we show that the southwards spread took place substantially more rapidly (1.50–2.27 km/y) than the eastwards spread (0.59–1.27 km/y). Such a faster southwards spread could be the result of a stronger cultural effect. To assess this possibility, we compare these observed ranges to those obtained from a demic-cultural wave-of-advance model. We find that both spreads were driven by demic diffusion, in agreement with most archaeological, linguistic and genetic results. Nonetheless, the southwards spread seems to have indeed a stronger cultural component, which could lead support to the hypothesis that, at the southern areas, the interaction with pastoralist people may have played a significant role.
At different times and regions over the world, human populations undertook agriculture as their new way of life, gradually replacing the previous hunting-gathering economies. These processes took place with different staple crops and livestock species, but in all cases the adoption of agriculture brought radical social transformations. Often it also led to the spread of farming to neighboring regions. This was the case for the agricultural practices that appeared in West Africa and spread across most of subequatorial Africa (excluding the rainforest and southwestern Africa). In contrast with Europe, in Eastern and Southeastern Africa agriculture brought with it the first metallurgy (i.e., the Early Iron Age, EIA) [1–4]. Many authors have related the spread of farming in eastern and southeastern Africa to that of Bantu languages [1–7]. Farming and Bantu languages would have reached the western part of East Africa, i.e., the Great Lakes area (Fig 1) by the last millennium BC, from where they would have spread eastwards and southwards, reaching the southernmost areas of their spread by 400 AD [1, 3, 8].
The spread of agriculture in most of southern Africa is often linked to the spread of Bantu languages, which from an origin in central Cameroon expanded southwards and eastwards, reaching the coast of East Africa and as far south as South Africa. Many authors have tried to elucidate the paths and nature of the spread into and/or around the rainforest area [4, 5, 12]. In contrast, here we have attempted to estimate the spread rates and asses their demic or cultural nature. We have focused on the area on which there is more agreement on the spread paths, namely the eastern half of subequatorial Africa, east of the rainforest. Agriculture in this area was characterized by the cultivation of cereals, unlike previous Bantu populations, and it is apparently upon reaching eastern Africa that the Bantu people adopted metallurgy [1, 3]. Therefore, this stage of the Bantu spread is singular enough to be studied separately from previous spreads.