A small collection of bird bones, recently identified as being those of a barn owl, have become the latest clues in the puzzle of Homo naledi, a strange species found deep inside an almost inaccessible section of the Rising Star Cave System in the Cradle of Humankind.
Three years ago the 1,500 hominid bones found in a chamber sparked a worldwide fossil frenzy, and ever since then the 15 skeletons from which the bones came have dumbfounded scientists who were struck by Homo naledi’s unusual combination of features.
They were also engaged in debates on the difficulty of dating the species, and the theory that it had buried its own dead.
More recently, it was finally dated at being only about 250,000 years old, and more debates about the cave system itself have been flaring up ever since.
Was it more open at some point, or was it always so inaccessible that the species’ being there at all beyond such a narrow chute is a mystery?
Now, a new paper published in the South African Journal of Science looks to what scientists have just identified as a single barn owl for at least some clues, if not definitive answers.
Lead researcher Ashley Kruger, from the Evolutionary Studies Institute at Wits University, told Times Select, “The most exciting thing is the possibility of knowing that once we date the owl bones it might give us a clue to the puzzle surrounding Homo naledi and the Dinaledi chamber because the owl may be able to tell us the last time the chamber was open before recent times when the cavers went in.”
The owl bones are believed to be more modern than the Homo naledi bones, as referenced by the “very thin calcite layer on top of the bones which signals a more recent deposition”.
The owl bones were also on top of the sediment.
“We know that Homo naledi fossils are between 236,000 and 335,000 years old, but we have no way of knowing when the chamber was open,” he said.
Kruger and fellow researcher Shaw Badenhorst believe the owl came through the system, taking a “similar route to the excavation”.
What also makes the owl so interesting is that it is the only other faunal remains found there.
“It is exceptionally unusual to not find lots of other fauna,” says Kruger. “We usually find carnivores of some type who have played a part in the assemblage of the bones, but with Homo naledi there are no traces of carnivore activity at all.”
Kruger’s paper provides different possible scenarios to explain the placement of the bird remains.
A modern owl “may have become lost in the system and, by way of flying around in the dark, found its way into the Dinaledi chamber”.
That’s the first hypothesis.
The second is that “the remains fell down the narrow chute – a 12m drop immediately above the Dinaledi system, and the only currently known accessible route into this system”.
Alternatively, but “less likely”, says Kruger, “the remains of this modern owl could have been introduced into the system by a caver carrying them in, possibly from the main entrance of the Rising Star Cave. However, why a caver “would carry remains into such a difficult to access area and then leave them there is not obvious”.
The final of the four hypotheses is that an alternative entrance into the Dinaledi chamber existed and explains the modern owl’s remains being there.
Professor Francis Thackeray, also from the institute, had argued controversially that the appearance of lichen on the hominid fossils indicate that there was once “an open area leading into the chamber”. In other words, another and more open entrance.
But, says Kruger, “we know from searching the cave system that there are no other paleo entrances so we don’t believe this to be true. But, the owl could be an important clue as to how things got into the chamber.”
He says “extensive and exhaustive exploration by cavers from the University of the Witwatersrand has, to date, failed to identify another entrance to the Dinaledi system”...