The discovery of Homo naledi, a newly discovered ancestor to modern humans, is being called one of the greatest fossil discoveries of our time.
Researchers at the University of the Witwatersrand, the National Geographic Society, and South Africa's Department of Science and Technology and National Research Foundation, worked together to unveil the largest single hominid fossil find on the continent of Africa. The results, published in the journal eLIFE and in National Geographic magazine, introduce us to an ancestor we never knew we had.
The H. naledi had a brain the size of an orange and a very slender body, standing about five feet tall and weighing about 100 pounds. Its teeth and skull were extremely primitive, and had apelike shoulders and curved fingers, which indicate an ability to climb and use tools. Its long legs and humanlike feet show that the H. naledi was good at long-distance walking.
In 2013, researchers and amateur cavers discovered more than 1,550 fossil elements in the Rising Star cave system in the Cradle of Humankind in South Africa. ("Naledi" means "star" in Sesotho, a local language in the country.) They were located in a chamber that was so hard to access, the team had to find a special team of slender women, who were dubbed "underground astronauts," to get through a small chute. The fossils have yet to be dated, but were of at least 15 individuals of the same species and had every part of the body represented multiple times.
The location of the fossils indicates that the H. naledi were deliberately disposing of its dead. Scientists had previously believed that disposing of the dead was a behavior unique to homo sapiens, but this may no longer be the case. The fossils, which represented humans of various ages, were found without any other animals nearby, aside from a few mice and birds which may have accidentally entered the cave. Not all scientists agree on this reasoning, The Guardian notes, but the scientists say they can't find any other plausible explanation.
The biggest immediate question that remains about H. naledi is its age. Says The New York Times:
Researchers analyzing the H. naledi fossils have not yet nailed down their age, which is difficult to measure because of the muddled chamber sediments and the absence of other fauna remains nearby. Some of its primitive anatomy, like a brain no larger than an average orange, Dr. Berger said, indicated that the species evolved near or at the root of the Homo genus, meaning it must be in excess of 2.5 million to 2.8 million years old. Geologists think the cave is no older than three million years.
And this is only the beginning of figuring out some of our earliest ancestors. "The chamber has not given up all of its secrets," Lee Berger, leader of the expeditions, said in a statement. "There are potentially hundreds, if not thousands, of remains of H. naledi still down there."