Wednesday, June 20, 2012

North Africans Consumed Milk Products 7 K.Y.A.

New research confirms an emerging consensus about when and where herding domesticated animals began to replace hunting and gathering in Africa (an activity that included the use of pottery and the collection of wild grains), and expands our understanding of how that herding society worked.

It happened in North Africa (including many places that are now too arid for this activity) and the Nile Valley after similar developments in the Middle East, but at about the same time that herding emerges in Europe. It happened before the main African origin crops were domesticated, and not long after the domestication in Egypt of the donkey. It appears to have involved both dairying and the use of cattle for meat from the start, or from very close to the start of a herding mode of food production.

The New Research

By analysing fatty acids extracted from unglazed pottery excavated from an archaeological site in Libya, the researchers showed that dairy fats were processed in the vessels. This first identification of dairying practices in the African continent, by prehistoric Saharan herders, can be reliably dated to the fifth millennium BC.

Around 10,000 years ago the Sahara Desert was a wetter, greener place; early hunter-gatherer people in the area lived a semi-sedentary life, utilising pottery, hunting wild game and collecting wild cereals. Then, around 7,000-5,000 years ago as the region became more arid, the people adopted a more nomadic, pastoral way of life, as the presence of cattle bones in cave deposits and river camps suggests.

Researchers . . . studied unglazed pottery dating from around 7,000 years ago, found at the Takarkori rock shelter in the Tadrart Acacus Mountains, Libya. Using lipid biomarker and stable carbon isotope analysis, they examined preserved fatty acids held within the fabric of the pottery and found that half of the vessels had been used for processing dairy fats. This confirms for the first time . . . . the importance of milk to its prehistoric pastoral people. . . .

"We already know how important dairy products . . . which can be repeatedly extracted from an animal throughout its lifetime, were to the people of Neolithic Europe, so it's exciting to find proof that they were also significant in the lives of the prehistoric people of Africa. . . .

[T]hese results also provide a background for our understanding of the evolution of the lactase persistence gene which seems to have arisen once prehistoric people started consuming milk products. The gene is found in Europeans and across some Central African groups, thus supporting arguments for the movement of people, together with their cattle, from the Near East into eastern African in the early to middle Holocene, around 8,000 years ago."

"While the remarkable rock art of Saharan Africa contains many representations of cattle -- including, in a few cases, depictions of the actual milking of a cow -- it can rarely be reliably dated. Also, the scarcity of cattle bones in archaeological sites makes it impossible to ascertain herd structures, thereby preventing interpretations of whether dairying was practiced."

From here.

The paper is: Julie Dunne, Richard P. Evershed, Mélanie Salque, Lucy Cramp, Silvia Bruni, Kathleen Ryan, Stefano Biagetti, Savino di Lernia. First dairying in green Saharan Africa in the fifth millennium bc. Nature, 2012; 486 (7403): 390 DOI: 10.1038/nature11186

The abstract of the paper notes that: "In the prehistoric green Sahara of Holocene North Africa—in contrast to the Neolithic of Europe and Eurasia—a reliance on cattle, sheep and goats emerged as a stable and widespread way of life, long before the first evidence for domesticated plants or settled village farming communities."

Other Evidence Regarding The Arrival Of The Neolithic Revolution In Africa

Notably, the find comes from the central Saharan highlands, not the Mediterranean coast or what is currently the African Sahel.  The find comes not from the "wet Sahara" period itself, but from the period when the Sahara was becoming increasingly arid.  There is an implication on the narrative from the press release journalism at Science Daily quoted above, that pastrolism may have not had much of an advantage over hunting and gathering until an increasingly arid climate in the Sahara tipped the scales in favor of pastoralism.

This date is older by more than a thousand years than the oldest reliably dated Central Saharan find of cattle bones.

The new research adds to the context provided by archaeological evidence of cattle bones in Africa, and insights provided by animal genetic data about the domestication of sheep and goats in Africa.

Cattle bones have been found at Nabta Playa, in the Eastern Sahara near the Middle Nile, dated to roughly the same time period as the evidence of dairy products in the most recent report in the central Saharan highlands.

There is archaeological evidence for cattle ca. 8,000 BCE in the Upper Euphrates Valley. Morphologically altered domestic cattle are not found in Central Anatolia until after 6,500 BCE, although morphological change appears empirically to follow domestication by about a thousand years in most cases. This Saharan find is roughly contemporaneous with the earliest evidence for dairying in Europe.

A 5000 BCE date would be after the domestication of the donkey in Egypt (camel domestication comes much later, probably after 1000 BCE).  As noted in the prior post on cattle domestication, around 5000 B.C.E. (i.e. at the same time as the milk residue find), "the remains of small livestock (sheep or goats) appear in several Middle Neolithic sites at Nabta. Because there are no progenitors for sheep or goats in Africa, these caprovines were almost certainly introduced from southwest Asia."  Another source puts caprovines in the region as much as a thousand years earlier.  That post also noted that:

[D]omestic cattle were present in coastal Mauritania and Mali around 4,200 years ago and at Capeletti in the mountains of northern Algeria about 6,500 years ago. At about that same time, they may have been present in the Coastal Neolithic of the Maghreb. Farther south in the Central Sahara, domestic cattle were present at Meniet and Erg d’Admco, both of which date around 5,400 years ago, and at Adrar Rous, where a complete skeleton of a domestic cow is dated 5,760 +/- 500 years B.P ].

Domestic cattle have been found in western Libya at Ti-n-torha North and Uan Muhuggiag, where the lowest level with domestic cattle and small livestock (sheep and goats) dated at 7,438 t 1,200 B.P. At Uan Muhuggiag, there is also a skull of a domestic cow dated 5,950 +/- 120 years. In northern Chad at Gabrong and in the Serir Tibesti, cattle and small livestock were certainly present by 6,000 B.P. and may have been there as early as 7,500 B.P. We are skeptical, however, about the presence of livestock at Uan Muhuggiag and the Serir Tibesti before 7,OO0 B.P., when small livestock first appear in the Eastern Sahara, if we must assume that these animals reached the central Sahara by way of Egypt and the Nile Valley. This also casts doubt on the 7,500 B.P. dates for cattle in these sites.

The earliest domestic cattle in the lower Nile Valley have been found at Merimda, in levels that have several radiocarbon dates ranging between 6,000 and 5,400 B.P. and in the Fayum Neolithic, which dates from 6,400 to 5, 400 B.P. These sites also have domes-tic pigs and either sheep or goats. In Upper Egypt, the earliest confirmed domestic cattle are in the Predynastic site of El Khattara, dated at 5,300 B.P. However, domestic cattle were almost certainly present in the earliest Badarian Neolithic, which dates before 5,400 B.P. and possibly were there as early as 6,300 B.P. Farther south, in Sudan near Khartoum, the first domestic cattle and small livestock occurred together in the Khartoum Neolithic, which began around 6,000 B.P.

Sorghum and pearl millet, two of the characteristic African domesticated plants were probably domesticated at least a thousand years after this earliest evidence of dairying in the Sahara. But, there is some evidence for at least proto-farming or intense collection of wild types of these plants are far back as 6000 BCE.  Arguably domesticated cattle bones are found in the Middle Nile as far back as 7000 BCE, but a few hundred years before that in the Middle Nile, ca. 7300 BCE, the evidence supports a hunting and gathering lifestyle rather than one associated with herding.

I have not focused recently on the dating of the arrival of Southwest Asian domesticated plants from the Fertile Crescent Neolithic into Africa in general, and North Africa in particular. 

A map in Fuller (2007) suggests the arrival of wheat and barley in Egypt ca. 5000 BCE-4000 BCE (after domestication in the Fertile Crescent ca. 7000 BCE), and in Nubia ca. 3000 BCE.  This would be well after the most recent dates for the arrival of pastoralism involving sheep, goats and cows in Africa.  Nothing in the report on the Takarkori rock shelter find suggests that evidence of pastrolism was accompanied by evidence of wheat and barley cultivation which one would expect to find in the same kinds of places that pottery relics disclosing milk storage or processing are found.

Also per Fuller (2007), pottery is found in both the Central Saharan highlands, where this find was made, and up and down the Nile basin, before 6800 BCE.

Evidence for Demic Diffusion?

One of the core debates in prehistory, which may have different answers in different places, is the extent to which the arrival of herding and farming that was derivative of the Neolithic revolution in the Fertile Crescent was spread via a process of demic diffusion (i.e. mostly through the migration of new peoples to those areas from Southwest Asia), or cultural diffusion (i.e. mostly through the adoption of the technologies by the indigeneous people in the areas to which the Neolithic revolution spread).

The new research does not offer very strong support, by itself anyway, for the assertion of one of the researchers quoted above that the arrival of dairying in the Sahara had a human component that was largely demic, as opposed to mostly involving merely cultural transmission of the knowledge necessary to carry on a pastoralist (i.e. herding) lifestyle.

The evidence from modern ethnographies and historic adoptions of pastoralism by hunting and gathering populations like the African San people, the Navajo, and the Australian aborigines, suggest that herding is a way of life that is more easily transmitted culturally to hunting and gathering peoples than farming. Indeed, one can make the case that early cultural adoption of herding before farming took hold in a region is critical to the continued vitality of populations ancestral to the early hunting and gathering populations that took up herding.

One can propose some general rules:

* Peoples who are hunters and gatherers when they first encounter farmers are mostly wiped out.
* Peoples who are hunters and gatherers who encounter herders who are not farmers have a decent chance of surviving as a people by becoming herders through cultural diffusion rather than demic diffusion. But, if they don't transition to herding, they will be wiped out unless they live someplace so marginal for farming and herding that no one wants to migrate into their territory.
* Peoples who are farmers persist genetically, even when they are conquered by outside pastoralists and swiftly assimilate the pastoralist superstate to their way of life.
* Peoples who are wiped out linguistically and/or culturally in a demographic transition leave stronger matriline traces than they do patriline traces.
* Peoples who rely on fishing for most of their sustainance are an intermediate case between terrestial hunters and gatherers, who have less staying power, and herders, who have more staying power, vis-a-vis farmers.

Genetic evidence on that point can, in my humble opinion, be argued both ways.  On one hand, there is evidence that the mostly Eurasian version of the latase persistance gene, which we would expect to spread with the migration of dairying peoples, is found in North Africa.  On the other hand, the population history of North Africa has many layers to it, some much more recent, and some of the important uniparental markers found in modern North African populations are characteristically African and show considerable continuity with the population genetics of pre-Neolithic North African populations revealed by ancient DNA from some North African sites.

Since latase persistance genes can carry a powerful fitness advantage for its carriers in times of food scarcity, a very small number of cases of introgression of this gene into a herding population that acquired herding technology and animals mostly as a result of cultural diffusion and trade could easily have been amplified in its frequency in the population afterwards while leaving only the most trace genetic evidence from selectively neutral sources.

Hat Tips to Dienekes and Maju whose posts I reviewed in preparing this one.

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