DNH 155: How Artec Space Spider helped reconstruct a 2-million-year-old skull
“This part of the story needs to be told,” said the voice on the other end of the line, that of Jesse Martin, La Trobe University researcher and co-lead author of the project. “Because without our Artec 3D scanner and software, the reconstruction of the DNH 155 cranium that everyone’s reading about simply wouldn’t have been possible.”
Martin along with his co-researcher Dr. Angeline Leece, together with Prof. Andy Herries and a team of others, put their Artec Space Spider to good use. The handheld 3D scanner was called upon during every step of the excavation and reconstruction of this extraordinary specimen of an ancient human cousin that vividly bears witness to microevolutionary changes within its species.
The full research paper was published in Nature Ecology & Evolution on November 9, 2020.
3D model courtesy of La Trobe University
When the team flew out from their home base of Melbourne, Australia to South Africa, their handheld Space Spider was protectively brought onto the plane as carry-on luggage. Days later, it was capturing the first DNH 155 skull fragments peeking out from a block of South African soil. And after hundreds of scans and months of exhausting work in the field and back at the lab, Space Spider was scanning the final reconstructed skull, to create images for the research paper itself.
Drimolen Main Quarry, South Africa. Photo courtesy of La Trobe University
The DNH 155, an almost complete skull of the species Paranthropus robustus, one of our distant relatives, was unearthed from the Drimolen Main Quarry, just north of Johannesburg, South Africa, in 2018 by field school student Samantha Good. While most fossil discoveries consist of merely a scattered tooth or bone or piece of skull, DNH 155’s hundreds of fragments were found in relatively close proximity to one another. But that doesn’t mean that they just clicked together like pieces of a jigsaw puzzle. Far from it.
Out in the field at Drimolen, with the help of Co-Director Stephanie Baker, over the course of several days, Leece carefully sliced large, fossil-embedded blocks of sediment from the ground. Once these were ready, Martin got down to work, using wooden sticks and other tools to painstakingly extract each skull fragment from the soil. To keep the dirt from falling apart, it had been infused with conservator’s glue, to hold everything in exactly the same place where it had been for eons.
To make the glue relinquish its grasp of the sediment and the fossils within, Martin would repeatedly wet the surface of the block with acetone to soften the glue. Then it was a matter of gently picking or brushing off millimeters of earth at a time, or even sucking the soil away through a drinking straw before the glue dried again. As soon as one of the fossils became evident, he would pick up his Space Spider and capture the fragment together with the entire surface of the sediment.
DNH 155 seeing the light again after 20,000 centuries. Photo courtesy of La Trobe University
In Martin’s words, “At this moment, there’s a kind of catch-22 involved, where you have to clean the fossil and preserve it, but to do that, you also have to take it apart. Which means you have to destroy that original location in order to accurately put the fossil back together.” He continued, “So, by 3D scanning each fossil layer with Space Spider, this gives me an exact record, and then later on I can put things back just where they were.”
And over the course of more than 300 hours, Martin and Leece did just that. With the collection of Space Spider scans running in Artec Studio software alongside, whenever there was a question about which position and location a certain fragment was found in, just a few easy clicks brought up its digital double, revealing the answer in seconds.
Space Spider was also crucial while reconstructing the DNH 155 from its 250+ fragments. “Each fossil was scanned numerous times throughout the manual reconstruction process, where we’re piecing together the fossil,” said Martin. “This provides us with an exact 3D record of each iteration during the reconstruction. So, to focus on DNH 155, with Space Spider, we scanned it numerous times in the field, and also back in our lab at the University of Johannesburg.”
Going into detail about the process, Martin elaborated, “Since we scan the larger pieces individually during reconstruction, we also have all of the internal detail of the cranium. If you think about it, no traditional method could get inside the cranium (except perhaps for CT scanning) once the skull is all back together, but because the Space Spider is so quick, it’s easy for us to scan the individual pieces prior to final reconstruction.”
Martin emphasized what he believes is one of the greatest advantages of the Space Spider. “Both of the traditional methods used by archaeologists, photogrammetry, and manual measurement with calipers and rulers, involve excessive handling of fossils. This means sooner or later the fossils are going to be scratched and chipped, if not worse.”
Using Artec Space Spider to scan a carnivore mandible excavated at the Drimolen Main Quarry. Image courtesy of La Trobe University
Martin added, “In fossil collections I’ve visited, time after time I’ve witnessed scratched and chipped bones and teeth from years of caliper measurements having been taken. With an Artec scanner, that will never happen, not even once.”
He explained further, “3D scanning with our Artec Space Spider involves no contact with the fossil in order to measure it precisely in just minutes. I can take 1000 scans of a hominid skull and there won’t be any damage, but if researchers do the same with the traditional method of calipers, which are either metal or plastic, there’s bound to be damage. Not to mention that various anatomical measurements with calipers require some weird and wonderful positioning of the fossil which, while possible, is dangerous and heart stopping.”
Martin described his usual scanning process with Space Spider: “I make one initial pass with the scanner, gently raising and lowering the scanner as I rotate the turntable holding the fossil. Then I’ll turn the fossil over and do the same for the other side. It takes just a few minutes at most. That will give me enough overlap and coverage of the surfaces for the fossil to be complete when I do the processing.”
In Artec Studio, Martin uses the eraser to remove the background, after which he aligns the scans. Following that, he does a global registration to register the scans, and then outlier removal and sharp fusion. He explained his choice as follows: “If I’m looking at hominid crania, I want to get a nice look at all the qualitative traits, so I set the accuracy to 100 microns. Then I’ll be able to see everything I want, like the temporal lines, cranial sutures, foramina, etc.”
After making sure the model is watertight, Martin puts the texture on, then exports the scan as a WRL file. “I choose WRL not only because it’s a universal format, but also because I like to have the texture separate from the geometry. When you’re doing the kind of work we are, you really want to take that color off, so you can look at the qualitative traits, since those are what we use repeatedly.”
Artec Studio screenshot of DNH 155 with texture on. Image courtesy of La Trobe University
Expressing the importance of working directly with the geometry of the fossil, Martin said, “When researchers view the scans with the color off, which is easy to do in Artec Studio, they can see much more than they had imagined, and certainly far more than they can see when looking at the fossil in person.”
Artec Studio screenshot of DNH 155 with texture removed. Image courtesy of La Trobe University
Martin went on, “To give you a striking example of this, I’ll tell you about what Space Spider revealed when we scanned a different hominid skull a few years back. This specimen is around two million years old, and was just 2 or 3 years old when it died. When you’re young, your cranial bones are relatively softer, because they haven’t fused yet, and your brain is growing quickly and pressing against the inside of your soft skull.”
“Now, you can’t see it when you’re visually examining the skull itself, even trained researchers can’t. It just looks like there are bumps and scratches. But on the internal surface of the cranium, when you’re in Artec Studio and you remove the texture from the Space Spider scan, there is the most magnificent imprint, like looking at a modern CT scan, of this 2-million-year-old hominid’s brain.”
Martin continued, “The brain left a distinctly clear imprint in the skull. You can see details such as the middle meningeal vessels, sulcal and gyral impressions, etc. We can easily interpret which areas of the brain are and are not present. Think about that for a moment. We’re now able to study a 2-million-year-old brain because of the imprints of that brain on the skull we scanned with Space Spider. Once you remove the texture from the scan, you can see everything in glorious detail.”
Researchers Angeline Leece and Jesse Martin with a 3D printed copy of DNH 155. Photo courtesy of La Trobe University
The DNH 155 has also been 3D printed from the Space Spider scans, with the results being nothing short of astounding. Even experienced researchers are amazed when first witnessing the lifelike 3D prints of this extremely fragile 2-million-year-old fossil.
Martin expressed how important the level of detail that Space Spider captures makes when reconstructing hominid crania. “We can actually 3D print fragments of skull we’ve scanned, and they’ll slide together perfectly with the actual fossil itself. All the sutures, all the edges match up flawlessly.”
Martin began using Space Spider in 2015, after being introduced to the scanner and Artec Studio software by Monash University’s Dr. Justin Adams. With only an hour of direct instruction from Adams under his belt, it took about ten hours of use for Martin to become proficient with it.
“That’s not because I’m some kind of genius with scanning, but rather it’s a testament to the technology and how intuitive it is. What’s best about it is not only its power and ease of use, but also its portability, which makes it our go-to solution that we take out into the field with us all the time,” Martin said.
Drawing of DNH 155 from Space Spider scans and photos, by researcher Giovanni Boschian
Ben Myers, Director of 3D Scanning at Melbourne-based Artec Gold Certified Reseller Thinglab, commented on the use of Artec 3D scanners in archaeology and beyond, saying, “We’re proud to have Jesse Martin and his colleagues at La Trobe University as our clients and support them in all the best ways. We believe that Artec 3D offers researchers and other professionals the utmost in 3D scanning solutions, from the desktop Artec Micro, the handhelds Eva, Space Spider, and Leo, on up to the tripod-mounted Artec Ray. Every possible digital capture application is now within reach.”
The scanning was supported by the University of Johannesburg, a La Trobe University PhD Scholarship to researcher Jesse Martin, and an Australian Research Council Discovery project Grant (DP170100056) to Professor Andy Herries.