And Paul Pettitt, an archaeologist at the University of Durham in England, says it’s possible that Homo naledi didn’t carry bodies, either for storage or burial. The corpses were probably carried away. “I’m not sure that the team has shown that this was an intentional burial,” he said.
As for carving and fire, experts say it’s not clear that Homo naledi was responsible for them. It is possible that it was the work of modern humans going into the caves thousands of years later. “It’s all inconclusive, to say the least,” said João Zilhão, an archaeologist at the University of Barcelona.
One way to test this possibility is to collect samples of carvings, charcoal and soot to estimate their age.
Hawks said this experiment was on the team’s to-do list but could take years because there are so many samples to test. Instead of waiting, said Dr. Hawks, the team decided to present their data now and start a conversation with other scientists about how to proceed.
“For me, it is much more important to document and share than to be right,” said Dr. Hawks.
If the researchers are correct, the findings will challenge some of the most important assumptions about human evolution. Humans and Neanderthals both had very large brains compared to earlier hominins, and paleoanthropologists have long assumed that larger size brought major benefits. There has to be an advantage to solving problems, evolutionarily speaking, of having a big brain. They need a lot of extra calories for fuel, and the baby’s large head puts the mother at risk of death in childbirth.
One of the benefits of a big brain is complex thinking. Neanderthals left impressive records of cooperative hunting, tool use, and other skills. And modern humans create symbols, use language, and perform other brain functions.
If hominins like Homo naledi could carve and dig graves, that means brain size is not important for complex thinking, said Dietrich Stout, a neuroscientist at Emory University who was not involved in the study.
“I think the interesting question is what exactly is the cerebrum needed for,” says Dr. Stout.