From late May to early July, a global team of students, paleoanthropologists, geologists and fauna experts from South Africa, Australia, the USA and Europe travel to Drimolen, a cave system north of Johannesburg in South Africa and within the “cradle of mankind”. This fossil excavation team, of which I am a member, arrives every year with renewed hope of discovering preserved and complete skulls of human ancestors. From the moment we step off the plane, we search seriously and expect our big break to come at any moment while we lie in wait between rocks and dirt.
In 2018, a female student excavator, Samantha Good, came across the adult male skull of one Paranthropus robustus, Lie upside down with your upper teeth showing. Over the next week, our two best dredgers, Angeline Leece and Stephanie Baker, carefully and persistently excavated the fossil until it could be removed, still largely trapped in sediment. Over the next two weeks, I continued their good job of removing the remaining sediment to rid the skull of its two-million-year-old sedimentary sarcophagus, and began carefully reconstructing the hundreds of individual fragments. While the Art Paranthropus robustus, A cousin of our own line is already known to science. The discovery of such a complete skull sparked a quest to reevaluate everything we believed we knew about our extinct relative.
One of the most exciting things about discovering human fossils is that they provide an opportunity to answer scientific questions about our own common origins that have never been answered before. In the case of the new Paranthropus robustus Skull labeled DNH 155, these new questions all centered on the pace and manner in which human microevolution – small changes within a species – occurred in response to a climate that evolved two million years ago.
Darwin’s theory of gradual evolution through natural selection predicts that populations will change over time, but seldom do we have the determination to “see” how these changes took place so long ago. In other words, we already have an excellent scaled-down perspective of human evolutionary history, but when we zoom in to evaluate minor changes, the picture becomes very pixelated and difficult to see. The discovery of the DNH 155 skull effectively gives us a close, but high-resolution snapshot of the small-scale microevolutionary changes that occurred between successive populations.
Digging up a fossil is a bit like opening a gift: you are never quite sure what you are going to get. In the case of the DNH 155 skull, the “wrapping” involved two million year old cave sediments and the “unpacking” a laborious and precarious process that took weeks. Nonetheless (and similar to a gift), our team had good reason to believe from day one that we would have the privilege of uncovering something very special together. The problem with archeology and paleoanthropology, however, is that excavating a fossil or artifact is inherently destructive. The sediments that contain such discoveries can tell us a lot about the age and context of the fossils themselves, and therefore we need to find innovative ways to preserve this record.
The situation with the DNH 155 skull was even more complex, as fossil human ancestors rarely leave the ground in one piece. In fact, the DNH 155 skull was made up of several hundred parts, some smaller than the average fingernail, and each part was incredibly fragile. Since it is not possible to dig up a fossil twice (and thereby destroy the original context), it is important that we get things right the first time. Because of this, 3D scanners changed the game.
DIGITAL STRUCTURE IN PROGRESS
My main job on site is the reconstruction of fossils. That is why I was commissioned to assemble the DNH 155 skull. It took about a week for the skull fragments and all of the sediment that had glued the pieces together to be completely removed from their original resting place in the main Drimolen quarry. As each of the 300 or so fragments was carefully removed, they were digitized with an Artec Space Spider, a professional 3-D hand scanner. The scanner picks up patterns of light that distort due to the geography of the object it hits and bounce back to the scanner – like a bat with sonar. In this case, however, light is reflected back and forth rather than sound. This technology was used to create high resolution digital records of every piece of the skull’s position in the sediment in the event that parts should unexpectedly loosen.
The first phase of the reconstruction was completed by manually assembling the parts. But even after the manual reconstruction, there were some elements of the skull that could not be placed because the contact point was too small or a tiny part of the edges had been lost. In these cases, Artec software was used to digitally position the parts in relation to each other. In particular, DNH 155’s face cannot be securely attached to the rest of the skull. This merger was achieved digitally. Although it could have been glued, joining the pieces together this way would have been risky and likely would have permanently damaged the fossil. The published reconstruction of the DNH 155 skull would not have been possible without the 3D technology, which would have been a major blow to the ability of other researchers to evaluate the fossil in the future.
DEMOCRATIZATION OF FOSSIL DATA
The reconstruction was only part of the research program aimed at unraveling the secrets of this rare skull. Many of the researchers working on fossils from South Africa cannot travel to Johannesburg to work on the originals. This is especially true for researchers who do not work in affluent institutions and for students with financial difficulties in general. For this reason, the Drimolen team has invested considerable capital in digitizing the DNH 155 skull and most of the fossil Drimolen assemblage. As a Ph.D. I am a student myself and am particularly interested in the potential of high quality 3D scanners like the Space Spider to democratize research by providing free and easy access to research quality data. While permissions and access to such data are controlled by the University of Witswatersrand (in the case of the Drimolen fossils), it is our ultimate intention to share our data with researchers, especially young researchers who have an issue related to the South African hominin Fossils.
Paleoanthropology has always been a combative and often exclusive discipline. I believe that 3D technology and the highly portable data it generates can help bring together a new generation of researchers and enable collaborations that would not have been possible before. The paleoanthropologist Gerhard Weber called for such a revolution twenty years ago. We’re not quite there yet, but we’re making progress.
This is an opinion and analysis article.