Archaeologists report earliest evidence for plant farming in east Africa

“Using our innovative approaches to excavation, we have been uniquely able to detect the arrival of domesticated plants and animals into Kenya and study the impacts of these introductions on local environments, human technology and sociocultural systems.”

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

Mueller used a flotation technique to separate remnants of wild and domesticated plant species from ashes and other debris in a hearth excavated at Kakapel. Although she has used this technique in her research in many other parts of the world, it is sometimes difficult to use this approach in water-scarce locations—so it has not been widely used in east Africa.

The scientists used direct radiocarbon dating on carbonized seeds to document the arrival of cowpea (also known as the black-eyed pea, today an important legume around the world) about 2,300 years ago, at about the same time that people in this area began to use domesticated cattle.

Researchers also found evidence that sorghum arrived from the northeast at least 1,000 years ago. They also recovered hundreds of finger millet seeds, dating back to at least 1,000 years ago. This crop is indigenous to eastern Africa and is an important heritage crop for the communities that live near Kakapel today.

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

The exceptional pea is pictured in the paper, and it represents its own little mystery. “The standard peas that we eat in North America were domesticated in the near east,” Mueller said.

“They were grown in Egypt and probably ended up in east Africa by traveling down the Nile through Sudan, which is also likely how sorghum ended up in east Africa. But there is another kind of pea that was domesticated independently in Ethiopia called the Abyssinian pea, and our sample could be either one!”

Many of the plant remnants that Mueller and her team found at Kakapel could not be positively identified, Mueller said, because even modern scientists working in Kenya, Tanzania and Uganda today don’t have access to a good reference collection of samples of plants from east Africa. (As a separate project, Mueller is currently working on building such a comparative collection of Tanzania’s plants.)

“Our work shows that African farming was constantly changing as people migrated, adopted new crops and abandoned others at a local level,” Mueller said.

“Prior to European colonialism, community-scale flexibility and decision-making was critical for food security—and it still is in many places.”

Findings from this study may have implications for many other fields, Mueller said, including historical linguistics, plant science and genetics, African history and domestication studies.

Mueller is continuing to work on identifying the wild plants in the assemblage, especially those from the oldest parts of the site, before the beginning of agriculture. “This is where human evolution occurred,” Mueller said.

“This is where hunting and gathering was invented by people at the dawn of time. But there has been no archaeological evidence about which plants hunter-gatherers were eating from this region. If we can get that kind of information from this assemblage, then that is a great contribution.”