The ash layer underneath probably deterred insects:
A cave in South Africa may hold early evidence of human innovation in sleep technology. A new paper published today shows how people 200,000 years ago put together grass and ash to make carpet-like structures to keep insects off them while they slept. The use of ash suggests they could control fire.
Lyn Wadley, an archaeologist at the University of the Witwatersrand in Johannesburg, South Africa, had worked at a different cave previously. There, she discovered 77,000-year-old bedding made from grass-like plants called sedges. “The sedges had medicinal plants on them, presumably laid there to serve as an insect deterrent,” Wadley wrote in an email. “I was fascinated by the idea that early Homo sapiens would have had such knowledge.”Katharine Gammon, “200,000 Years Ago, Humans Created Beds of Grass and Ash to Sleep” at Inside Science
Some of the ash at Border Cave was from camphor wood, a medicinal herb.
They must have known how to control fire if they had easy access to ash. Like the Neanderthals, they get smarter with each cycle of papers.
See also: Early hominins (480,000 years ago) were—wait for it!—more sophisticated than thought. Maybe Darwinians should canvass at LinkedIn for a new subhuman.
Human evolution at your fingertips