1. The hyena ate a person(s). This happens even today, so it's very possible.
2. The hyena scavenged a dead person's body.
3. Somehow the hyena consumed a blob of human hair. Hey, you never know. If the hyena were hungry enough, it might have sampled all kinds of weird things.
What's clear, at least, is that humans were at the site.
NEWS: Ancient Humans May Have Dined on Hyenas
As the researchers wrote, "Hair provides evidence of inland occupation by archaic Homo sapiens or modern humans."
The hair lacked scales, which could provide yet another useful clue.
"A lack of hair scales has been documented in human hair subject to pathology, a condition observed when studying our diabetic colleague's hair as part of the human comparative sample," Taru and Backwell explained.
Life in a cave could have led to many bad hair days, though. "Abrasion of the hair resulting from inhabiting rock crevices" could have led to lack of scales, according to the authors.
It's impressive how valuable an old hair stuck in hyena poop can be. Future investigations will likely focus on the region in South Africa to learn more about our human ancestors there and how they interacted with other species.