Tooth enamel from ancient cattle could help explain how the practice of herding spread through Africa long ago, new analysis reveals.

The tsetse fly, which can carry illnesses, including sleeping disease, was thought to play a major role in the history of human civilization in the Sahara region. However, this new study shows the role played by that insect may have been over-estimated.

The Sahara Desert experienced a period of growth 5,500 years ago, forcing residents of the area to migrate south in search of water. That movement of ancient people ceased 2,000 years ago, an event which many researchers believe was brought about, in part, by infections caused by the tsetse fly.

Remains of cattle from the Gogo Falls region of Kenya were examined, studying ratios of different chemical isotopes. Investigators found that vegetation found east of Lake Victoria was far different 20 centuries ago than it is today. This plant life could have played an important role in the migration from the northern coast of Africa, down into central and southern regions of the continent.

Examination of tooth enamel from the animals suggests that vegetation was plentiful in the region, and people there likely consumed food from both wild sources and domestic production. Since people stayed in the area for a significant amount of time, it is unlikely that tsetse flies were as dangerous in the region as previously believed.

"We studied the chemical signature of teeth in wild antelopes and domestic plant-eating animals -- cows and sheep or goats -- and found they all were eating a lot of grass in the Lake Victoria Basin," Kendra Chritz, lead author of a new paper announcing the results of the study, said.

Although the exact route taken by populations during that time is still uncertain, it was previously thought that the migrants avoided the area around Lake Victoria, due to the presence of the dangerous flies.

"[O]ur isotopic findings support the notion that herders may simply have interacted with hunter-gatherer groups already living in these areas, adapting to their foraging styles. This suggests that social factors may have played a greater role than previously thought in subsistence diversity during the spread of pastoralism in Eastern Africa," Fiona Marshall, an anthropologist at Washington University in St. Louis, said.

University of Utah investigators studying the genetic code of humans descended from southern people found that a genetic mutation, allowing the consumption of non-human milk, developed early in those populations. This suggests that humans populated that region well before investigators previously estimated.

Investigation of the ancient migrations was profiled in the journal Proceedings of the National Academy of Sciences.

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