Earth Observatory Blog
How Ancient Herding Communities Shaped the African Plains
Every year, millions of tourists travel to east Africa to watch millions of wildebeest, zebra, and other animals travel across the plains in one of the last “pristine” environments in world.
What they might not realise is that around 3,500 years ago, this area of the world was also home to people who primarily subsisted on food produced by their cattle, sheep, and goats. Although these migrations of wildlife are often foremost in popular imaginings of the east African plains, a growing body of research shows that both ancient and modern pastoral societies have also had a hand in shaping parts of the east African grasslands.
A team of archaeologists, including Dr Michael Storozum, a Research Fellow at the Earth Observatory of Singapore, recently published a paper in Nature, that identifies ancient herding activities as enriching soil with micro- and macro-nutrients through their livestock corral practices over 3,000 years ago. As recent Amazonian studies have done, this paper reveals that human activities have influenced ecosystems traditionally thought of as “pristine.”
For decades, archaeologists have wondered how ancient pastoral societies influenced the savanna because they have found little evidence of hunting activities in some prehistoric pastoral societies despite abundant and accessible wildlife.
Archaeologists have often relied on ecological research on abandoned modern pastoral homesteads that shows that when pastoralists corral their livestock at night, the accumulation of dung inadvertently creates nutrient enriched hotspots that attract a wide range of insects, rodents, and birds. The increased presence of smaller animals attracts larger wild animals, including zebra and wildebeest, as well as cattle.
Although these nutrient hotspots might have existed in the past as well, neither archaeologists nor ecologists knew how far back in time pastoral societies might have influenced east African environments.
Published in Nature on 29 August 2018, our study uses a combination of high-resolution elemental and isotopic methods to identify high mineral nutrients, particularly calcium and phosphorus, and 15N enrichment in soils at five archaeological sites, pushing the human imprint on these landscapes back over 3,000 years. We verified that these sediments were actually livestock dung by using microscopic and infra-red spectroscopic methods to identify diagnostic markers found within sediments derived from animal dung.
This research supports the assertions of ecologists who argued that humans might have had long term positive influences on east African savanna ecosystems. These results indicate that for over 3,000 years, the earliest east African pastoralists might have been instrumental in creating the nutrient rich soils necessary to support east Africa’s famed wildlife. When we scale our findings up, our results provide a deeper time context for archaeological and paleoenvironmental studies on the past one or two thousand years of eastern and southern Africa’s environmental history.
Our team of experienced archaeologists from the Earth Observatory of Singapore, Washington University in St. Louis, the University of Illinois, Urbana, the National Museums of Kenya, and local Maasai residents and other Kenyan field workers, made this research possible. In particular, our collaborator, Purity Kiura of the National Museums of Kenya, was instrumental in helping us to develop the project. Senior researchers from diverse institutions undertook the field work and analyses. I, myself, studied the archaeological sediment and soil elemental composition with a team of scholars who also analysed carbon and nitrogen isotopes in the laboratory.
As with all studies, our findings merely open the door to ask other archaeological, paleoenvironmental, and ecological questions. How did these ancient herders enhance east African savanna diversity? Were these practices unintentional, or did these ancient pastoralists know about their long-term affects? How large an area do these nutrient hotspots cover and how do they differ across east Africa’s diverse grassland ecologies? To address some of these questions through a combination of soil surveys and geoarchaeological work, I visited an archaeological site in northern Tanzania recently. Now, we have a few answers, but future research will be necessary to understand the deep human imprint on east African landscapes.