In Human Origins—the Phillips Academy interdisciplinary science course being taught this fall by Peabody Museum director Ryan Wheeler—our once-a-week extended period gives us an opportunity to do some hands-on work with ancient tools or fossil human casts. During our extended period on Wednesday, September 21 we visited The Nest, the campus makerspace at the Oliver Wendell Holmes Library. There we worked with Claudia Wessner, makerspace coordinator, who was helping us 3D print a model of the world’s newest fossil hominin, Homo naledi.
In 2013 cave explorers alerted scientists to the presence of fossils in the Rising Star cave system in South Africa. Within two years an international team led by paleoanthropologist Lee Berger had recovered the remains of at least fifteen individuals represented by over 1,500 specimens. In September 2015 Berger and his associates published their preliminary findings in the online, open source journal eLife, dubbing the new fossil Homo naledi. Naledi means “star” in the Sotho language. The fossil hominin has features that are similar to the ape-like Australopithecines and early members of our genus, Homo. Even more exciting for students and scholars is the availability of 3D files for 108 of the fossils, available on Morphosource. Despite the availability of this data, Homo naledi remains a bit of a mystery. For example, the fossils remain undated, though the excavators suggest they may date between 1 and 2 million years ago. This would make them contemporaries of early members of our genus, like Homo habilis (2.4 to 1.4 M years ago), as well as Homo erectus (1.89 M to 143,000 years ago). Dates will help show if Homo naledi is a potential ancestor of ours or another branch on the already bushy human family tree.
For our 3D print we selected the proximal end of a femur. Berger and his associates report in their eLife article that Homo naledi’s femur is unique. The femoral neck—the part connecting the ball-like head of the bone with the shaft—possess two pillars that define a sulcus, or shallow groove. The origins and functions of these features remain unclear. This was, however, an opportunity to continue our ongoing conversation about the femur and its relationship to bipedalism in modern humans and our fossil ancestors. Claudia had wisely made several prints, including one life sized and one larger than life; another print was ongoing while we visited. We compared these 3D prints to several models and casts from the Peabody Museum, including the femur of modern humans, Homo erectus, Neanderthals, and robust and gracile Australopithecines. It was clear that Homo naledi did indeed combine ancient and more modern features. For example, the hands and feet of Homo naledi are very human-like, while the trunk and crania are more like those of Australopithecines. We saw this when comparing the 3D print with the femurs of Homo erectus and Australopithecines.
Students were quite engaged with this lesson and there was considerable interest in printing other Homo naledi fossils. Claudia demonstrated the technology involved in creating 3D scans, manipulating the files with 3D software, and generating the print. The models produced of the femur took from 5 to 9 hours. We looked at the 3D files of the reconstructed skull and marveled at the software estimates of 60 hours to create a life sized 3D print. A number of the students were already quite familiar with the makerspace and the 3D technology and shared their own experiences with 3D scanning and printing.
We learned at the end of September that this was not the first time 3D data for a fossil human had been publicly shared. In his 1911 publication on the Neanderthal skeleton excavated at the French site of La Chapelle-aux-Saints, Marcellin Boule included stereo views of the skull that could be viewed with a stereoscope. Lydia Pyne—in her terrific 2016 book Seven Skulls: The Evolution of the World’s Most Famous Human Fossils—talks about Boule’s work and the stereo views (also see her blog post that highlights free, online versions of Boule’s publication and animated gifs of the skull). Unfortunately, it is difficult (or down right impossible) and expensive to obtain plaster casts or models of most human fossils. Hopefully the sharing of the Homo naledi 3D data will continue with future discoveries and with older fossils that exist in museum collections.
Conversations about the 3D print of the Homo naledi femur continued in classes well after the visit to the makerspace as we talked about the origins of bipedalism, its great antiquity to at least 6 or 7 million years ago and the fossil hominin Sahelanthropus tchadensis, and the multiplicity of ideas about the adaptive advantages and disadvantages of bipedalism in hominins (there are at least 13!).