In the winter of 2015, La Trobe Graduate Researchers Jesse Martin and Angeline Leece were reconstructing what they thought were the remains of a baboon, excavated from a piece of rock in The Drimolen, South Africa.
The pair were part of an expedition to collect and study fossils from the site, which is part of a the archaeological treasure trove known as ‘The Cradle of Humankind’.
But what they were actually piecing together was something altogether more astounding: 150 fragments of a two-million-year-old Homo erectus cranium, the oldest known fossil of a species that had never before been identified in South Africa.
The findings have just been detailed in a La Trobe study, published in Science.
In what sort of environment was the artefact found? Can you describe where you were working?
Jesse: The Drimolen cave in South Africa looks a little bit like an old roman amphitheatre – a large circular hole on the side of a hill, with one edge, gently rolling into the centre of the hole, and the other marked by sharply rising dolomite walls. The cranium itself was embedded in the breccia (which is the ancient dirt, rocks and fossils turned to stone over millions of years) and had recently been exposed.
Angeline: The image that comes to mind when someone hears the word ‘cave’ isn’t really accurate. These palaeo-caves are completely filled with sediment which, over time, has hardened into breccia. After years and years of erosion, the Drimolen cave has lost its roof as well. So, what we were left with is a large hole in the ground where the hard breccia is slowly turning back into soft sediment. It is in this soft material where we primarily work. The Homo erectus cranium – named DNH 134 – was first found in material that was still quite hard and had to be carefully removed to expose the bone fragments.
Did you know immediately what you’d found?
Angeline: When the first pieces were discovered, they were still encased in partially hardened sediment, so there wasn’t immediate recognition! At first, the team thought it may have been a baboon skull. As Steph Baker – a University of Johannesburg researcher, study co-author and Drimolen Co-Director – and I began cleaning it, we started to realise that it was probably a hominin. It wasn’t until a few weeks later, once Jesse had put more pieces together, that we realised it may belong to Homo erectus.
What happens when a discovery of this magnitude takes place? Are you celebrating or cheering?
Jesse: All the above! Hominin fossils are so rare that they could all, probably comfortably, fit into the tray of one ute. Fossils of early Homo (including Homo erectus) are even rarer. When we realised that we had the world’s oldest Homo erectus fossil, we were extremely excited.
Angeline: The reaction at first was quite restrained because, well, I don’t think any of us could believe it! Once we knew what we were looking at, though, it was very exciting. These things are so rare that this kind of discovery calls for a celebration or two!
How long did it take you to understand the significance of your discovery?
Jesse: Once we had worked out that the fossil was the world’s oldest Homo erectus cranium, we very quickly had to consider the broader implications for humanity’s evolutionary story.
Angeline: Once we realised that this specimen likely belonged to Homo erectus, the significance was pretty clear. We had some idea that the site was approximately two million years old, so it was pretty clear we’d stumbled on something special.
What is it like to make a discovery that helps re-write our understanding of the past?
Jesse: It’s a team effort, and my first thought was how lucky I am to be part of such a diverse and dedicated team, which can bring many different scientific methods to bear. Our colleagues are spread all over the world – from the United States to South Africa, Australia to Germany – and everyone must work together to fashion a new understanding of such a unique and important fossil.
Angeline: It’s an amazing experience. I’m lucky to be part of an amazing team and lucky to be able to experience this with them. There’s certainly a special moment when you realise what you have found, what it means, and the fact that – for this brief time – you’re the only one who knows this little puzzle piece exists. It’s the kind of experience that creates quite a close bond between teammates.
How was the artefact preserved?
Jesse: The fossil is beautifully preserved, but that doesn’t mean it comes out all in one piece! In fact, the DNH 134 cranium is made up of more than 150 individual fragments glued back together. What that means is that reconstructing the fossil is like trying to complete a massive jigsaw puzzle, with heaps of pieces missing, and without knowing what the end product is supposed to look like.
Angeline: The excavation of fossils from the sediment can sometimes take as long as the reconstruction itself. This is because, as Jesse said, we want to make sure that we find every little piece of the puzzle. The more of the fragments (some of which are only a few millimetres across) we can find, the more complete the fossil cranium will be.
What this your first big dig?
Jesse: The Drimolen excavation in 2015 was my first major archaeological/palaeoanthropological excavation, so it was quite a nice way to start!
Angeline: I had participated in the excavation of a Native American settlement when I was still studying in the United States. Drimolen is a different kettle of fish in many ways – from the excavation techniques to the material recovered, it’s certainly the longest-running project I’ve ever been a part of.
What made you want to pursue archaeology as a career?
Jesse: I have always had a fascination with the past, particularly human evolution, and my PhD supervisor, Professor Andy Herries (Head of the Department of Archaeology and History at La Trobe), has been able to provide me, and many other students, with the opportunity to pursue our individual passions.
Angeline: I have always had an interest in archaeology – even as a child. Professionally, it all started with a human evolution course I took up to fill a requirement in the first year of my undergraduate degree. From then on, this was what I wanted to do. I went straight from that class, taught by Professor David Strait (who is also a co-author on the Science paper), to his office and asked him what I needed to do to make that happen.
After advising me through my degree, he suggested I work at the La Trobe Drimolen field school. It’s here I met Professor Herries for the first time and it’s where we spoke about my future, as well as the future of the site. I flew home to New York already having decided I would move to Australia! I can’t thank these senior people enough for the opportunities they have provided me.
What does the online transition, triggered by COVID-19, mean for the future of archaeology?
Jesse: It is a challenge for students, tutors, and lecturers, but it also presents opportunities to experiment with new ways of engaging with educational content. In the case of La Trobe’s Department of Archaeology and History, staff have been working tirelessly using world-class 3D scanning technology to digitise our fossil and stone tool collections, so students can experience human evolutionary fossils and stone technology from all over the world in HD and 3D.
Angeline: I think it is very difficult for both students and teachers. Archaeology is, at its core, a hands-on profession. However as with the excavation and reconstruction of fossils, archaeologists know how to be patient, resilient, and innovative. Unlike two million years ago, and indeed as recently as a few decades ago, human societies can draw down on a range of technologies and innovations to stay connected. For archaeology, I think that the next six to 12 months will see researchers experimenting with new ways of conducting research, analysing existing finds, and planning the eventual return of fieldwork.