Border Cave stretches deep into the mountains on the border of South Africa with Eswatini.
A. Kruger
By Cathleen O’Grady
Border Cave is a deep hole in a cliff face, high in the Lebombo Mountains of South Africa. Protected from the elements, the site has produced bones, tools and plant material that paint a detailed picture of the lives of human inhabitants for more than 200,000 years. Now there is a new sketch to order: Plant continues to point to evidence that cave dwellers used grass beds about 200,000 years ago. Researchers speculate that cave dwellers laid their bedding on ashes to repel insects.
The preserved bedding will be part of a series of other “incredible discoveries” from the African archaeological record, said Javier Baena Preysler, an archaeologist at the Autonomous University of Madrid who was not involved in the study. But other researchers point to uncertainty in the dates and markets that absent a time machine, scientists have to speculate on exactly how ancient humans used the stepped grass and ash.
Lyn Wadley, an archaeologist at the University of the Witwatersrand, made the discovery while digging with her Border Cave team. One morning she noticed white spots in the brown earth of the sediment as she dug. “I looked it up with a magnifying glass and realized it was plant spores,” she says.
Wadley has carefully removed small pieces of the sediment and stabilized it in small “jackets” of gypsum plaster. Under the microscope, she identified that plant material as belonging to the family of Panicoideae of grass growing in the area.
Archaeologist Lyn Wadley saw small white markings in the Border Cave sediment that turned out to be compressed, preserved plant material.
L. Wadley
The amount of grass suggests that humans deliberately brought it into the cave, Wadley says. The sediment shows recurring layers of plant and ash, she says, suggesting to her that the material was used to create a clean and comfortable floor surface.
The researchers can not be sure that people were sleeping on the grass. But they describe it as “bedding”, because it probably seemed like people would use the comfortable floor surface for sleeping. It is “the most plausible interpretation”, Baena Preysler agrees.
The layer of sediment that contains the grass lies deep in the excavated layers in the cave, near the mountain ground. Researchers have dated two isolated teeth in the same layer until about 200,000 years ago by measuring how much radiation the tooth enamel was exposed to. The date ranges for the two teeth are wide, with one slightly older than 200,000, and the other slightly younger.
Dates of just using these two teeth are a bit shaky, says Dani Nadel, an archaeologist at the University of Haifa who was not involved in the work: “Sometimes such dates are not very accurate.”
If the dates hold, the Border Cave beds would be the first evidence of people using camp beds. The second oldest known plant bed, in the Sibudu Cave in South Africa, is dated to 77,000 years ago, although there is tentative evidence of bedding plant layers from about 185,000 years ago in Israel.
The bedding itself “tells us nothing about the complex cognition of humans,” says Wadley. Numerous other animal species, including birds, rodents, and other primates make nests. But material discovered next to the grass indicates more extensive behavior. Ash, as well as burning grass, wood and bone, suggest that the inhabitants of the cave periodically burned the bedding, possibly to rid the area of ’smelly beds and pests’,’ says Wadley. Some of that burnt wood came from the broad-leaved camphor forest, a species that is still used as an insect repellent in South Africa.
The repeated layers of ash and plant material suggest that old people deliberately lay bedding over ashes, Wadley says. People all over the world, including in present-day Cameroon, have long used various types of ash to repel and kill insects by blocking their breathing and biting devices. Evidence in Border Cave suggests that humans deliberately used ash and medicinal plants to keep their camps clean and pest-free, Wadley and her colleagues reported today. Science.
“However, it is very difficult to prove this,” says Dan Cabanes, a microarchaeologist at Rutgers University, New Brunswick. “You can not ask these people.”
Still, he says, the discovery reveals how much of the botanical record is likely to be missing at archaeological sites worldwide. Plants make up a large part of the diets of modern humans, in addition to a variety of other uses, from clothing to medicines, so there is good reason to think that our ancestors relied heavily on plants in their daily lives, since Cabanes. But the subtle traces of ancient plants can be easily overlooked, he says, “How much of this story do we miss?”
