PHILADELPHIA ‚ÄĒ The first unequivocal evidence that humans in prehistoric Saharan Africa used cattle for their milk nearly 7,000 years ago is described in research by an international team of scientists, led by researchers from the University of Bristol in the United Kingdom and including Kathleen Ryan of the University of Pennsylvania Museum of Archaeology and Anthropology. Their work was published today in Nature.
By analyzing 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 B.C.E.
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, utilizing 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 suggested by the presence of cattle bones in cave deposits and river camps.
Domesticated animals were clearly significant to these people. The engraved and painted rock art found widely across the region includes many vivid representations of animals, particularly cattle. However, no direct proof that these cattle were milked existed until now.
Researchers from the University of Bristol‚Äôs School of Chemistry, with colleagues at Sapienza, University of Rome, studied unglazed pottery dating from around 7,000 years ago, found at the Takarkori rock shelter in the Tadrart Acacus Mountains in Libya.
Ryan, a consulting scholar in the Penn Museum‚Äôs African Section and an author on the study, had previously collected data on reference animal fats and plant remains from Kenya.
"Though the Kenyan remains have so far not turned up any evidence of dairying there, they were valuable in that they served as controls in our study of the Libyan samples," Ryan said.
The researchers used these reference samples to inform lipid biomarker and stable carbon isotope analyses of preserved fatty acids held within the fabric of the pottery.
‚ÄúWithout this collection the project would not have come to fruition in the way it has,‚ÄĚ said Richard Evershed, a professor in Bristol‚Äôs School of Chemistry and co-author on the paper.
The team found that half of the vessels had been used for processing dairy fats. This confirms for the first time the early presence of domesticated cattle in the region and the importance of milk to its prehistoric pastoral people.
‚ÄúWe already know,‚ÄĚ said Julie Dunne, a doctoral student in Bristol‚Äôs School of Chemistry and lead author of the study, ‚Äúhow important dairy products such as milk, cheese, yogurt and butter, which can be repeatedly extracted from an animal throughout its lifetime, were to the people of Neolithic Europe, so it‚Äôs exciting to find proof that they were also significant in the lives of the prehistoric people of Africa.
‚ÄúAs well as identifying the early adoption of dairying practices in Saharan Africa, these 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.
‚ÄúThe 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,‚ÄĚ she said.
‚ÄúWhile the remarkable rock art of Saharan Africa contains many representations of cattle ‚Äď including, in a few cases, depictions of the actual milking of a cow ‚Äď it can rarely be reliably dated,‚ÄĚ Evershed said. ‚ÄúAlso, the scarcity of cattle bones in archaeological sites makes it impossible to ascertain herd structures, thereby preventing interpretations of whether dairying was practiced.
‚ÄúMolecular and isotopic analysis of absorbed food residues in pottery, however, is an excellent way to investigate the diet and subsistence practice of early peoples. It‚Äôs an approach my colleagues and I have previously applied to successfully determine the chronology of dairying, beginning in the Fertile Crescent of the Near East and spreading across Europe.‚ÄĚ