What was going on at the Rising Star cave complex?

Thirteen years ago, the basic building blocks of human evolution seemed to be in place. Then Rick Hunter and Steven Tucker really upset the applecart.

They are recreationist speleologists, those who enjoy exploring caves. It takes a lot of nerve to launch yourself head first into a tiny hole in a cliff and this is what they did at the Rising Star cave complex in South Africa. One fissure, known as "Superman’s Crawl", is so narrow that you have to put your hands forward to make headway. Then you have to climb up the Dragon’s Back before descending nearly vertically into a chamber 100m into the limestone massif. There, they encountered a floor littered with human remains, the "Dinaledi Chamber".

News reached Lee Berger, an anthropologist at the University of Witwatersrand, but he was unable to follow in their footsteps: one tiny aperture has a minimum width of just 18cm. Instead, he recruited by social media, female archaeologists hand-picked for being slender enough to navigate their way down into the fossil chamber and brave enough to try. There, they recorded and lifted for scientific analysis, the remains of at least 20 individuals. These had all the hallmarks of very early hominins, that should have dated back at least a million years. But they actually date to between 241,000-335,000 years ago.

They simply don’t fit into the human evolutionary pathway. Their brains match in size, those of a chimpanzee, they were able to walk as do modern humans, but also climb trees with ease. No stone tools have been found with them. They look like an evolutionary cul-de-sac, for they lived at the same time as early modern humans. There is an unanswered question: what are they doing buried away in this virtually inaccessible cave?

Last week, a new conundrum had to be faced with a publication based on a protein called amelogenin that has been extracted from tooth enamel. This can be used to determine whether the tooth comes from a male, or a female. Specialists are now in virtual disbelief, because the research has concluded that every single individual of this new species so far recovered was female, even the infants and children.

Burying females alone in one place is unheard of in human history until about 5000 years ago. So whatever was going on at the Rising Star cave? Several possible explanations have already been forthcoming, but the simple answer as of now, is that we simply don’t know.