Researchers have uncovered evidence that members of a mysterious archaic human species buried their dead and carved symbols on cave walls long before the earliest evidence of burials by modern humans.
The brains belonging to the extinct species, known as Homo naledi, were around one-third the size of a modern human brain.
The revelations could change the understanding of human evolution, because until now such behaviors only have been associated with larger-brained Homo sapiens and Neanderthals.
The findings are detailed in three studies that have been accepted for publication in the journal eLife, and preprints of the papers are available on BioRxiv.
Fossils belonging to Homo naledi were first discovered in the Rising Star cave system in South Africa during excavations in 2013. The cave system is part of South Africa’s Cradle of Humankind, a UNESCO World Heritage Site encompassing an area where scientists have found fossils of multiple ancient human ancestor species — remains that are helping to unlock the story of human evolution.
Paleoanthropologist and National Geographic Explorer in Residence Dr. Lee Berger and his team of “underground astronauts” have continued their work in the extensive, dangerous caves to better understand the extinct hominins, or ancient human ancestors.
Now, the research team has discovered the remains of Homo naledi adults and children that were laid to rest in the fetal position within cave depressions and covered with soil. The burials are older than any known Homo sapiens burials by at least 100,000 years.
Mark Thiessen/National Geographic
During the work to identify the cave burials, the scientists also found a number of symbols engraved on the cave walls, which are estimated to be between 241,000 and 335,000 years old, but they want to continue their testing for more precise dating.
The symbols include deeply carved hashtag-like cross-hatchings and other geometric shapes. Similar symbols found in other caves were carved by early Homo sapiens 80,000 years ago and Neanderthals 60,000 years ago and were thought to have been used as a way to record and share information.
“These recent findings suggest intentional burials, the use of symbols, and meaning-making activities by Homo naledi. It seems an inevitable conclusion that in combination they indicate that this small-brained species of ancient human relatives was performing complex practices related to death,” said Berger, lead author on two of the studies and coauthor on the third, in a statement. “That would mean not only are humans not unique in the development of symbolic practices, but may not have even invented such behaviors.”
Crawling through caves
Exploring the labyrinth-like Rising Star cave system and its chambers isn’t for the faint of heart.
The team has mapped over 2.5 miles (4 kilometers) of the caves so far, which have a vertical depth of 328 feet (100 meters) and expand for more than 656 feet (200 meters) in length, said the studies’ lead geologist Dr. Tebogo Makhubela, senior lecturer of geology at the University of Johannesburg.
The cave system includes deadly steep drops and tiny passageways like Superman’s Crawl, a tunnel measuring 131 feet (40 meters) long and 9.8 inches (25 centimeters) across, requiring the researchers to belly crawl their way through, said Dr. Keneiloe Molopyane, National Geographic Explorer and lead excavator of Dragon’s Back Expedition (named for one of the cave’s features).
Berger said he had to lose 55 pounds (25 kilograms) to enter the cave’s precarious chambers in 2022.