Eyes in the sky: My experience with ‘ground-truthing’ aerial-sensed traces of ancient hominin activity

by Beth Tippett Barr.

I can’t remember how or when I first connected with stone tool hunting. I’ve always been fascinated with rocks and pebbles and stones – as a child I had jars of stones and pebbles that I had collected along the way. A few years ago, I was hiking a section of the Appalachian trail in Tennessee when an unnaturally-shaped stone caught my eye. It turned out this was my first ‘find’: A native American stone arrowhead. A few months later I was in Mongolia doing a 7-day ultramarathon (which was what the time on the Appalachian trail had been training for), and again another unusual rock caught my eye – this one wasn’t quite as clear in what its purpose was (probably a spear tip), but it was most definitely worked stone. I think that’s probably when I really became interested in finding more stone tools. It was absolutely fascinating to me that someone so very long ago had left this evidence of their existence. I started looking through Facebook to see who else was out there with this interest, and stumbled across some very interesting groups, all of which had encouraging and helpful people in them.

Ikept seeing the name “Michika Takahashi” in the comments – and she’d talk about seeing traces of hominin activity in the landscape wherever people had found artefacts. This seemed very logical to me – I was already using Google maps to closely look at places I wanted to go hiking or exploring, and it was obvious to me that there are things visible from the sky that we don’t see when we’re standing on the ground. Michika was helping a guy in South Africa find places to go stone tool hunting, and he always seemed to find stone tools. I started wondering whether she could help me too.

By this time, I was living in Kenya, the stomping grounds of the famous Leakey family, a country well known for its history of human fossils and hominin discoveries. I had a birthday coming up and decided that all I wanted for my birthday was to spend a day stone tool hunting. My husband agreed to take me wherever I wanted to go, and so I tentatively reached out to Michika for guidance. She was on board in a heartbeat and got me so excited for my upcoming trip. I told her there was a place south of Nairobi called Oloorgesailie which had the largest cache of stone hand axes ever found: They were discovered by the Leakeys and were so abundant that they were left in-situ and an entire museum built around them. This is an incredibly hot and dry part of Kenya now, but at one time it was on a lake’s edge, and along with the stone tools, fossils of now extinct animals and hominins were also found in the immediate area of the hand axes. I knew I wanted to go see this archaeological site, and Michika said she’d be my eyes in the sky and let me know if she could see any traces in the nearby area that might indicate a good place to go stone tool hunting myself. Little did I know! Next thing my phone is blowing up with WhatsApp messages and location pins because she’s seeing SO much in the entire area within a 10km radius of the museum. I saved locations on google earth that she thought looked the most promising, and off I went, husband reluctantly in tow.

The small but mind-blowing museum had a very interesting mural on the wall of stratigraphic layers in the area, made from actual materials from each later. It showed the layers of the earth in the area, and how they’d changed over the years with various climactic events, including a massive volcanic eruption that created a different-colored layer of volcanic ash, and which had been dated at 350,000 years ago. The importance of this mural to my future explorations in this area didn’t immediately register with me, but I thankfully took a photo at the time that I’ve referred to a few times since then. Before we left the museum, I asked the custodian what we were supposed to do if we found similar stone tools when we were hiking in the area. He told me that they didn’t care about what was found outside of the museum property. I realize now that was probably not the same answer an archeologist would have provided, but at the time I just took him at his word.

We drove about six kilometers away from the museum to where Michika had indicated a cluster of sites that she thought were worth starting with. If you’ve ever been to the badlands in America, that’s what the Oloorgesailie area is like – very dry, very rugged, but with lots of thornbush filled gullies and crumbly edged drop-offs. I was most concerned at first that I’d bump into a venomous snake, but tried not to think too hard about it – or stick my hands under any rocks! The entire area Michika pointed me to is roughly square-shaped, around 10km by 4km, with a road running along one long end, and a year-round river at the other long end. There’s an overall slope downhill from the road to the river, and gullies have formed over the years as flash floods periodically pour through there.

We drove off-road as far as the landscape would allow, and parked under a scrubby acacia tree; the only shade I could see. While we were getting ready to go for our hike, a couple of men appeared from who-knows-where to tell us we were parked on their land. They were both dressed in their finest as they were heading home from church, and were very pleasant and helpful. We paid them the equivalent of about 10 euros to spend the afternoon wandering around the area. They must have thought we were mad. It was a scorching hot day – probably around 38C (100F). What we didn’t know was that it was only going to get hotter – once down in the gullies the heat seemed to concentrate and bounce off the walls and it was probably closer to 50C (120F).

I realized pretty quickly that the areas Michika had indicated ran alongside what was probably one of the gullies I was looking at, although the google maps image only showed a line that could have been anything. Having never ever done anything like this before I didn’t know where to start, and then it occurred to me that I’d just seen the stratigraphic mural in the museum and if I could align the colors with the cliff walls and river gully walls we were seeing, then at least I could find the layer that I was most likely to be successful with.

We walked around for what felt like hours, not seeing anything remotely resembling a stone tool…. Remembering again the stratigraphic layers, we decided to head further towards the river until we knew we were below the red layer of volcanic ash that we had seen in the mural. What we hadn’t realized until then was that we were actually a good 20-40 metres higher altitude at our starting point than the museum was, so we weren’t even anywhere near the ash layer! We climbed down into the large gully and headed towards the river. Sure enough, we started seeing the layers that were on the mural, and pretty soon we found the red layer. For some reason, that alone made me feel excited; as though somehow the place I was in suddenly had just as much prospect as the museum area to reveal something amazing. And sure enough – we started seeing flakes. The distinctive shape made from the intentional impact with another stone were unmistakable. Even to someone as clueless as I was…. And then I happened to look down at just the right time, and there, half sticking out of the gully wall, was a hand axe. A giant one. It was old and very weathered, but oh my. I was beyond excited. I found out later it is actually a cleaver. But what joy to realize I was seeing something that no human had seen for hundreds of thousands of years. I marked the spot on the map where we found it and excitedly sent photos off to Michika, who’d been waiting patiently on the other end of the phone, waiting for updates.

This experience had a profound impact on me. From connecting with Michika on what would be the first of many adventures, to realizing just how little we actually know about pre-written history. Michika’s aerial analysis methods are met with disbelief and scorn when discussed with most archaeologists. Some cynics have said “of course you were going to find stone tools; look at the area you were searching, so near to the museum. But keep in mind that it is a large and inhospitable area. And archeologists have been scouring that landscape for decades, looking for more artefacts. We found our cleaver within an hour of getting down to the right layer. Yes, the odds were certainly stacked in our favor given the archaeological site a few kilometres away, but Michika’s aerial viewing skills were what led us almost directly to the right location.

Other archaeologists have argued that “hominins didn’t have dwellings” and “hominins were nomads so they had no need of settlements”… but I believe it’s truly important to remember “absence of evidence is not evidence of absence”. We don’t know something until we know it. A good example of this is the discovery from just last year: Wood that had been worked into a Lincoln-log style boardwalk were found in the cliff edge at the bottom of a waterfall in Zambia and dated to 476,000 years old, millenia before most archaologists will admit that hominins were even capable of such work. The dating methods are new and widely accepted as valid. And somehow that incredible finding, which should have shaken up the world of prehistoric archeology and made the professionals question everything they think they know about early hominin life on earth, seems to have just faded away. Ignored until it disappears because it doesn’t fit the preconceived notions of how things were. “Facts” which were established based on what we knew decades ago.

When it comes to settlements or dwellings of prehistoric hominins, we need to admit that we just don’t know. And we may never know anything for sure. But what I do know from my lifetime of exploring the far-flung corners of Africa, is that all animals, humans included, want somewhere to call their own. Somewhere they feel safe and protected. Whether it’s a house, or a cave, or a dwelling carved out of existing landscape features. And if you think about it, it seems quite logical that even nomads would camp in the same area when following migrating animals as their main food source. After all, people still do that in Mongolia and other places today. Nomadic doesn’t mean homeless.

What Michika sees when she looks on google earth I can’t always see. Sometimes I can make out distinct almond-shaped areas where she sees larger evidence of ancient human activity. But when she sees the smaller traces, I can rarely see pick it out of a screen shot. But I’ve been “ground-truthing” for her in Kenya and Malawi for nearly 3 years now, and when she points me in a particular direction, I always find something. I do have a doctorate degree, but I have no training in formal archeological methods: I’ve never dug test pits, or joined any digs. But what I do know is that science is only science when you approach the unknown with an open and enquiring mind, willing to explore and learn more about the things we don’t yet know about, and being able to acknowledge when what we thought we knew perhaps wasn’t the whole story.