Ancient watercourses and biogeography of the Sahara explain the peopling of the desert
Drakea et. al.
PNAS 2011
Evidence increasingly suggests that sub-Saharan Africa is at the center of human evolution and understanding routes of dispersal “out of Africa” is thus becoming increasingly important. The Sahara Desert is considered by many to be an obstacle to these dispersals and a Nile corridor route has been proposed to cross it. Here we provide evidence that the Sahara was not an effective barrier and indicate how both animals and humans populated it during past humid phases. Analysis of the zoogeography of the Sahara shows that more animals crossed via this route than used the Nile corridor. Furthermore, many of these species are aquatic. This dispersal was possible because during the Holocene humid period the region contained a series of linked lakes, rivers, and inland deltas comprising a large interlinked waterway, channeling water and animals into and across the Sahara, thus facilitating these dispersals. This system was last active in the early Holocene when many species appear to have occupied the entire Sahara. However, species that require deep water did not reach northern regions because of weak hydrological connections. Human dispersals were influenced by this distribution; Nilo-Saharan speakers hunting aquatic fauna with barbed bone points occupied the southern Sahara, while people hunting Savannah fauna with the bow and arrow spread southward. The dating of lacustrine sediments show that the “green Sahara” also existed during the last interglacial (∼125 ka) and provided green corridors that could have formed dispersal routes at a likely time for the migration of modern humans out of Africa.
Posted by Evergreen (Member # 12192) on :
quote:Originally posted by Evergreen: Ancient watercourses and biogeography of the Sahara explain the peopling of the desert
Drakea et. al.
PNAS 2011
The Peopling of the Sahara During the Holocene
We hypothesize that the differences in animal resources between the northern and southern Sahara during the early Holocene influenced the way it was peopled by humans. The north–south contrast in Saharan species ranges are remarkably similar to some key lithic, bone tool, and linguistic spatial distributions, suggesting that the peopling of the region during the early Holocene humid phase was driven by cultural adaptations that allowed exploitation of specific fauna. The early Holocene archaeology of the Sahara is characterized by a regional distribution of specific archaeological cultures, such as those defined by barbed bone points, fishhooks, Ounanian arrow-points, and, more controversially, pottery. The Sahara today is largely populated by speakers of Afroasiatic languages, Berber and Arabic, with some Nilo Saharan languages (Teda-Daza and Zaghawa) in the region of Northern Chad, and Songhay cluster languages scattered across Mali and Niger. However, it is clear that this situation is recent; Berberspeaking Tuareg moved into the Central Sahara ∼1500 y ago and the spread of the Hassaniya Moors into Mauritania probably dates from the 15th Century. Before this time, the central and southern Sahara are thought to have been populated by Nilo-Saharan speakers. The Nilo-Saharan language phylum is both widespread and strongly internally divided, suggesting considerable antiquity. Its greatest diversity is in the east, where a large number of small branches are found suggesting the original locus of expansion. Although fragmented into enclave populations today, the presence and pattern of relic populations in the northern desert points strongly to a much wider distribution in the past, covering the region from the Ethio-Sudan borderland to Mauritania and southwest Morocco. It has long been suggested that Nilo-Saharan languages might correlate with barbed bone points, the so-called “Aqualithic” superimposes the sites of known barbed bone points on a map of current Nilo-Saharan languages, showing a remarkable similarity in spatial distribution, and also a notable correspondence with Holocene distribution of large aquatic species. It appears that the expansion of aquatic resources in the Holocene made the Sahara attractive to populations with existing fishing and riverine hunting skills. Their ability to hunt hippopotamus and crocodiles and to catch a wide variety of deepwater fish species would have propelled a rapid dispersal from east to west and into the central Sahara, to judge by the numerous branches of Nilo-Saharan in the east. Their movement further north would have been restricted by the absence of many of these species. However, the presence of an isolated Nilo-Saharan population (the Koranje, a branch of Songhay) and a barbed bone point in Northwest Africa near the headwaters of the catchment of the Soura River, the river that links the Atlas mountains to the lakes in the Ahnet-Mouydir basin, forming a corridor from the central Sahara to Northwest Africa, indicates that a few groups may have traversed the green Sahara using the most promising routes. There is direct linguistic evidence that Nilo-Saharan populations exploited these aquatic resources in the form of a widespread cognate for “hippo” from Gumuz in Ethiopia, to Songhay in Mali. SI Appendix, Table S2 shows similar forms for “crocodile,” although in this case the cognates are split between eastern and western languages. We hypothesize that the other economic revolution that occurred in the Sahara at approximately the same time was the southward spread of the bow and arrow. North African hunters would have observed the new abundance of large and unfamiliar land mammals to the south, notably elephant and giraffe. In a dispersal inverse to that of the Nilo-Saharans, they would have been attracted southward to hunt these animals with the bow and arrow. The “Ounanian” of Northern Mali, Southern Algeria, Niger, and central Egypt at ca. 10 ka is partly defined by a distinctive type of arrow point. These arrowheads are found in much of the northern Sahara (Fig. 3) and are generally considered to have spread from Northwest Africa. This view is supported by the affinity of this industry with the Epipalaeolithic that also appears to have colonized the Sahara from the north. No Ounanian points occur in West Africa before 10 ka, suggesting the movement of a technology across the desert from north to south around this time. Our model envisages the initial Holocene repopulation of the Sahara being carried out by two separate populations practicing two quite different resource exploitation strategies: (i) aquatic foraging using bone point and fish hook technology, and (ii) savanna hunting using the bow and arrow. By linking the distribution of the Nilo-Saharan language phyla to the archaeological distribution of aquatic- and terrestrial-adapted technologies, we explain the pattern of human repopulation of the desert in terms of the changing faunal distribution, which is in turn dictated by the nature of trans- Saharan hydrological linkages.
Posted by zarahan (Member # 15718) on :
Interesting that they link Nilo-Saharan to barbed hooks of the aqualithic culture. How do you think the two strategies- aqualithic and savannah-hunting played out in the Nile Valley?
Posted by Doug M (Member # 7650) on :
quote:Originally posted by zarahan: Interesting that they link Nilo-Saharan to barbed hooks of the aqualithic culture. How do you think the two strategies- aqualithic and savannah-hunting played out in the Nile Valley?
Played out? This wasn't a game. People hunted and fished. If the rains were there and fish were there they fished. If the savanna was there and animals in it they hunted. People did what they had to do given the environment. This pattern of hunting and fishing developed in the interior of Africa in places like the Sahara and elsewhere over thousands of years. The migrations of populations to the Nile Valley bought this basic system of subsistence with them. And it is this same system of subsistence that allowed humans ultimately to migrate out and populate the entire planet as a result of learning to adapt to changing climates by developing various subsistence strategies.
You see that in the tombs with scenes of hunting and fishing which in many ways are no different from scenes of hunting and fishing found all over Africa from time immemorial.
Posted by The Explorer (Member # 14778) on :
Did the authors factor in Niger-Congo speakers at all in their early Holocene Saharan people movement scenarios, or does the reader have to suppose they did not exist at this time?
Posted by Sundjata (Member # 13096) on :
Well said Doug. Though in addition to Explorer's inquiry, I'm curious as to their position on Afro-asiatic. Asserting that the Afroassiatic speakers present today in the southern and central Sahara are recent, what do they suggest was the starting orientation of the original Afroasiatic speakers?
Evergreen, is this explored any further in the paper? They seem to imply the north, attributing them to this northern cultural group, but I'm not sure how deep in antiquity they go with this language phylum and whether or not they address the other branches outside of the more recent Berber and Semitic.
Posted by The Explorer (Member # 14778) on :
About the "Tuareg" thing, i.e. their supposed movement into central Sahara at ca. 1500 years ago. From where, one might query. Tamasheq/"Tuaregs" are visibly absent in eastern Africa, i.e. if Libyan territory is not considered. Whatever may be said of their ultimate proto-Imazighen eastern African ancestors sometime ca. early-mid Holocene, nothing comes to mind that would suggest that the actual ethnogenesis of the Tamasheq ("Tuaregs") occurred outside of either central or western Africa; common western African hg L mtDNA markers [e.g. hg L1b, L2b, L3e2b, L3e3, L3f1] had been identified in Tamasheq samples from as far as Tahala and Jebel al Awaynat in Libya, which suggests that the Tamasheq there were not totally isolated from western African originated folks, likely western African Tamasheq counterparts.
Posted by Doug M (Member # 7650) on :
quote:Originally posted by The Explorer: About the "Tuareg" thing, i.e. their supposed movement into central Sahara at ca. 1500 years ago. From where, one might query. Tamasheq/"Tuaregs" are visibly absent in eastern Africa, i.e. if Libyan territory is not considered. Whatever may be said of their ultimate proto-Imazighen eastern African ancestors sometime ca. early-mid Holocene, nothing comes to mind that would suggest that the actual ethnogenesis of the Tamasheq ("Tuaregs") occurred outside of either central or western Africa; common western African hg L mtDNA markers [e.g. hg L1b, L2b, L3e2b, L3e3, L3f1] had been identified in Tamasheq samples from as far as Tahala and Jebel al Awaynat in Libya, which suggests that the Tamasheq there were not totally isolated from western African originated folks, likely western African Tamasheq counterparts.
Exactly. Most Tuareg cultural connections, along with the genetic connections you mention are in west Africa. This includes dress and metallurgy which all has a West African root.