Discovery of 2,300-year-old ancient crops challenges modern view of African agriculture

Recent discoveries at the Kakapel rock shelter in Kenya shed light on the origins and development of ancient agriculture in East Africa, detailing the introduction of crops such as cowpea and challenging past perceptions of African agriculture.

Ancient plant remains discovered in Kenya shed light on the history of agriculture in equatorial East Africa. This region is considered important for early agricultural development, but there has been little physical evidence of ancient crops until now.

In a new study recently published in the Proceedings of the Royal Society BArchaeologists from Washington University in St. Louis, the University of Pittsburgh and colleagues report the largest and most dated archaeobotanical record from the interior of East Africa.

Until now, scientists have had little success in collecting ancient plant remains in East Africa and, as a result, have had little idea of ​​where and how plant cultivation began in this vast and diverse area that includes Kenya, Tanzania and Uganda.

“There are many accounts of early agriculture in East Africa, but there isn’t much direct evidence of the plants themselves,” said Natalie Mueller, assistant professor of archaeology in Arts & Sciences at the University of Washington and co-first author of the new study. The work was conducted at the Kakapel rock shelter in Kenya’s Lake Victoria region.

Mueller discovered an unusual crop: the wild pea, burned but perfectly intact. Peas were not previously considered to be among the earliest agricultural crops in this region. Credit: Courtesy of Proc. Royal Soc. B

“We discovered a vast array of plants, including many crop remains,” Mueller said. “The past shows a rich history of diverse and flexible agricultural systems in the region, in contrast to modern stereotypes about Africa.”

The new research reveals a pattern of gradual introduction of different crops from different regions of Africa.

In particular, the cowpea remains discovered in the Kakapel rock shelter and directly dated to 2,300 years ago represent the first documented arrival of a domesticated crop – and likely an agricultural lifestyle – in East Africa. Cowpea is thought to have originated in West Africa and arrived in the Lake Victoria Basin at the same time as the spread of Bantu-speaking peoples migrating from Central Africa, the study authors said.

“Our findings at Kakapel reveal the earliest evidence of domesticated crops in East Africa, reflecting the dynamic interactions between local pastoralists and incoming Bantu farmers,” said Emmanuel Ndiema of the National Museums of Kenya, a project partner. “This study illustrates the National Museums of Kenya’s commitment to uncovering the deep historical roots of Kenya’s agricultural heritage and fostering an appreciation of how past human adaptations can inform future food security and environmental sustainability.”

A constantly changing landscape

Located north of Lake Victoria, at the foot of Mount Elgon, near the Kenya-Uganda border, Kakapel is a renowned rock art site that contains archaeological artefacts attesting to over 9,000 years of human occupation in the area. The site has been recognised as a Kenyan national monument since 2004.

“Kakapel Rockshelter is one of the only sites in the region where we can observe such a long sequence of occupation by so many diverse communities,” said Steven T. Goldstein, an anthropological archaeologist at the University of Pittsburgh (WashU PhD ’17), the study’s other first author. “Our innovative excavation approaches have allowed us to uniquely detect the arrival of domesticated plants and animals in Kenya and study the impacts of these introductions on local environments, human technology, and sociocultural systems.”

Mueller joined Goldstein and the National Museums of Kenya to lead excavations at the Kakapel rock shelter site in 2018. Their work is ongoing. Mueller is the lead scientist for plant research at Kakapel; the Max Planck Institute for Geoanthropology (in Jena, Germany) is another partner in the project.

Mueller used a flotation technique to separate the remains of wild and domesticated plants species She has used this technique in her research in many other parts of the world, but it is sometimes difficult to use this approach in areas where water is scarce, so it has not been widely used in East Africa.

The scientists used direct radiocarbon dating on charred seeds to document the arrival of cowpea (also known as black-eyed cowpea, now an important legume worldwide) about 2,300 years ago, around the same time that people in the region began using domestic livestock. The researchers also found evidence that sorghum arrived from the northeast at least 1,000 years ago. They also recovered hundreds of millet seeds, dating back at least 1,000 years. The crop is indigenous to East Africa and is an important heritage crop for the communities that live near Kakapel today.

One unusual crop Mueller discovered was the field pea (Pisum), burned but perfectly intact. Peas were not previously considered part of early agriculture in this region. “To our knowledge, this is the only evidence of peas in Iron Age East Africa,” Mueller said.

The pea featured in the article is a mystery. “The peas we eat in North America were domesticated in the Near East,” Mueller says. “They were cultivated in Egypt and probably ended up in East Africa down the Nile through Sudan, which is probably how sorghum ended up in East Africa. But there is another kind of pea that was domesticated independently in Ethiopia, the Ethiopian pea, and our sample could be either!”

According to Mueller, most of the plant remains his team found at Kakapel could not be positively identified because even scientists working in Kenya, Tanzania and Uganda do not have access to a good reference collection of East African plant samples. (As part of a separate project, Mueller is currently working on building such a comparative collection of plants from Tanzania.)

“Our work shows that African agriculture has constantly evolved through migration, the adoption of new crops, and the abandonment of others at the local level,” Mueller said. “Prior to European colonialism, flexibility and community-based decision-making were essential for food security – and they still are in many places.”

The results of this study could have implications for many other fields, Mueller said, including historical linguistics, plant science and genetics, African history and domestication studies.

Mueller continues to work on identifying wild plants in the assemblage, particularly those from the oldest parts of the site, before agriculture began. “This is where human evolution happened,” Mueller said. “This is where hunting and gathering were invented by humans at the dawn of time. But there is no archaeological evidence to show what plants hunter-gatherers in this area were eating. If we can get that kind of information from this assemblage, then it will be a big contribution.”

Reference: “Early agriculture and crop transitions at Kakapel Rockshelter in the Lake Victoria region of eastern Africa” by Steven T. Goldstein, Natalie G. Mueller, Anneke Janzen, Christine Ogola, Rita Dal Martello, Ricardo Fernandes, Sophia Li, Victor Iminjili, Sara Juengst, Anthony Odera Otwani, Elizabeth A. Sawchuk, Ke Wang, Emmanuel Ndiema and Nicole Boivin, July 1, 2024, Proceedings of the Royal Society B.
DOI: 10.1098/rspb.2023.2747