Exploring the great serendipity of prehistoric tracks

Chinyere Opia 00:00

South Africa's southern Cape coastline is emerging as one of the best places for ichnologists to study the fossilized tracks and traces left by ancient animals and humans. This has allowed for the study of track sites for footprints and patterns made in the sand which have shed more light on the movements and distribution of Southern Africa's historic inhabitants. Welcome, to another exciting episode of Science in Africa. This is a Nature Africa podcast for African scientists and Africans interested in science. I am Chinyere Opia.

Engela Duvenage spoke to Charles Helm, associated with the Nelson Mandela University about some of these finds. Take a listen.

Engela Duvenage 00:46

Just over two decades ago, as the new millennium began, it was really extremely rare to find tracks left by our ancient human ancestors dating back more than about 50,000 years. The first such track was found in 1966, at Nahoon in the Eastern Cape of South Africa. Subsequently, three other sites were also identified – in Langebaan in South Africa, in Tanzania and in Kenya. By 2022, 24 such sites were already known, found along South Africa’s Cape coast, in East Africa, from the UK and the Arabian Peninsula. Seven new sites along South Africa’s Cape coast were announced in a new paper in Ichnos, the international journal of trace fossils. Their ages range between 71 thousand years and 153 thousand years old. I’m Engela Duvenage, and I’m chatting about these finds to lead author Charles Helm, an ichnologist associated with the Nelson Mandela University in South Africa. Please tell us a bit more about the work of ichnologists such as yourself.

Charles Helm 02:09

Yes, thank you, Engela. Ichnology is the study of tracks and traces. It's really pattern recognition, being able to perceive patterns and then correlating that with the paleoenvironment, the age of the rocks in which you're seeing these things. But ichnology can be as simple as walking along the beach and interpreting the tracks of whoever's gone there, which is people who have gone before you, of whichever animals that have been on the beaches and the dunes, that's what we call neoichnology. Paleoichnology is the study of the fossil record in terms of tracks and traces.

Engela Duvenage 02:47

You've made many finds over the course of two, three decades now. How do the tracks that you describe in Ichnos look like and how and where were they found?

Charles Helm 02:58

Right. As you said, we found 350 vertebrate track sites along the 350-kilometre stretch of coastline in southern Africa. And the majority of those are buck, a few lions, a few crocodiles, elephants, things like that. There's actually a minority that were made by humans. And we actually consider ourselves very privileged to have identified seven sites which have a human origin. Some of them are footprints. Some of them are patterns made in the sand by our ancestors in those dunes and on those beaches. In some cases, we've got footprints and patterns. In one case, we've got a pattern with knee impressions as someone was kneading a pot to make it. And sometimes it's just footprints. But the counterintuitive things are that sometimes these footprints are not on the surface, as hollows on the surface, in other words the dune surface on which they were made. Sometimes they might be infill layer such that the layer blew in with sand that filled in those tracks. And so often at times, we find these things on the ceilings of caves, for example. And so, we have to go into these caves and look at their ceiling for the infill layer. And that's counterintuitive. And that's possibly why we find things that other people have not found before, because we understand how these things form.

Engela Duvenage 04:20

Tell us a bit more about the significance of the tracks that you found that you said to be 153,000 years old. Where were those found and who found them and how did you find them?

Charles Helm 04:32

Well, my wife and I actually came across them. My goodness, it must have been about 2014. And we were very intrigued by them. And we kind of thought they looked like hominids’, but we didn't have the confidence at that time to say for sure. And then we brought an international expert out from Colorado, a friend of mine, my mentor, and we looked at them together. And then he found it, Martin Lockley, he found this one beautiful track which just clinched it, made it beyond any reasonable doubt that this is a human track. So, as you say, 153,000 years old. And there's something about footprints that you know, you can look at this thing and you can say, well, it looks like it was made yesterday. You can just put yourself there so easily, which is something that bones don't really, really do that easily for people that look at them. But fortunately, this is in the Garden Route National Park. So it's in a protected area. It's on a very beautiful, pristine portion of the coastline. So, it's a very evocative place.

Engela Duvenage 05:35

And how were you able to actually date your find, how do people go about doing that?

Charles Helm 05:42

Yeah, so that's a really good question. For example, you mentioned the Nahoon tracks which were 124,000 years old, discovered in 1966. In those days that took them about three or four decades to work out how old they were, because the technology just wasn't there. And now, it's relatively easy in that we have a wonderful technology called OSL, Optically Stimulated Luminescence. And we've got a wonderful colleague, Carr, in Leicester, in England. And so, from these certain sites, we actually took samples, one sample from each sites, a sample being 20 centimetres cubed. And that’s pretty heavy. We reduce them in size, and we send them to him. And it takes a good few month, up to a year, to get them dated. When we get the dates, we're confident in the accuracy, but even so, when we say 153,000, it's not exact, it's within a few 1,000 years, but it's in that ballpark. So, it's close. And it's essentially, you know, how long since those grains of sand were last exposed to sun. That's what we measure because this would have been a dune surface exposed to sun and then buried. So, we are measuring, ultimately, how long this has been buried for and then re-exposed, just recently, through coastal erosion, high tide, storm surges, climate change, because we're going to be getting more and more of that, because the storm surges are getting bigger. So, more sites are going to be exposed.

Engela Duvenage 07:10

So you will be busy. What do the new tracks and all of the tracks that you find along the southern Coast tell us about the lives of our ancestors? And why are you in a way always fascinated by the fact that it's being found along the southern Cape Coast of South Africa?

Charles Helm 07:32

Well, the great serendipity is what we call it. This is one of the places where Homo sapiens found its feet, if we can say that and you know, we've got evidence through the archaeological record of sophisticated tools and use of fire and bone tools and jewelry, all sorts of things like that. But tracks can give a different kind of information. So, they can complement the traditional record in ways that the traditional record can't do on its own. So, things like were we running, were we walking? The group dynamics. Were there babies and kids, or just adults? Were we using sticks to propel ourselves? Were we making patterns in the sand as we were walking just like we do on beaches today? We see sandcastles. Normally nowadays, it's initials and hearts that you see on the beach. But you know, that's an ancient practice that goes way back into antiquity. And we are very privileged to be able to see those things today. But, you know, ichnology complements the trace fossil record and the traditional body fossil records and archaeological records. Everything is stronger if we combine everything together. But essentially, Ichnology has been a relative late comer on the Cape south coast. But the serendipity is that this area where we found our feet, as I've said, happens to have this incredible record in these, these rocks, which we call aeolianites which have cemented sand dunes and cemented beaches and it's one of the best aeolianite records in the world. And it didn't have to be that way. You know, we could have had just the people here, but they didn't leave a record for us to interpret. Or there could be these beautiful rocks elsewhere with no evidence of humans on them. And it's just a coincidence, and it's a wonderful coincidence that these two things happened in the same place. So, we're just really privileged to be doing this work on the Cape south coast of South Africa.

Engela Duvenage 09:37

And it's also a great thing that these people who have the foresight to look out for them such as yourself. Thank you for talking to us.

Charles Helm 09:46

Thank you.

Chinyere Opia 09:48

Thank you Engela Duvenage and Charles Helm for joining me today and shedding light on the fascinating world of research in Africa and thank you for joining us on this episode of the Science in Africa podcast. If you are interested in finding out more on the important work being done by African research scientists, check out our Nature Africa website at nature.com/natafrica; and until next time, I am Chinyere Opia.