This is the remains of a simple structure from the Stone Age that may be the oldest evidence yet of early humans building with wood.
It was uncovered in Zambia by a team of archaeologists.
The construction is basic: a pair of overlapping logs, fitted together with a notch.
It's nearly half a million years old and provides a rare look at how ancient human relatives were working with wood and changing their environments, authors wrote in a study published Wednesday in Nature.
Usually, wood rots quickly when it’s exposed to the elements, which has left us with little evidence of how our ancient relatives used the material, but these materials were submerged in the river, which helped preserve them.
So when his team uncovered the logs in 2019, they were still able to see telltale signs that early humans had shaped them — carving out a notch in the upper log, tapering off the ends and leaving tool marks across the surface.
"You could see the individual chop marks really clearly. It's extraordinary. Everything just looks so fresh you think 'it can not be this old'. And when Geoff's dates came through, 477,000 (years old), I thought wow! It's just amazing. We were lucky," says Larry Barham, Professor of African Archaeology at University of Liverpool and one of the report authors.
And it was pinning down the dates that was key to this discovery.
Figuring out just how old posed its own challenge, since traditional dating techniques couldn't get deep enough into the past.
In this study, researchers used a new method called luminescence dating, which uses tiny minerals in the sand to estimate how long materials have been buried.
"What I've been involved in is a method called luminescence dating and this enables us to fill in this gap that other dating techniques really can't touch. And in particular what's useful about it is that we can apply it to the sands that the river deposits themselves, so we don't have to find special materials, we don't have to find tephra (volcanic ash) or anything particularly, it's just common minerals that occur in these sediments. And we can date those to give an age range," explains Geoff Duller, Professor of Quaternary Science at Aberystwyth University and a report author.
Barham and his team dug up the log structure — plus a handful of wooden tools — from a riverbed site that sits above a waterfall in Zambia.
They think the crossed logs could have been the base for a bigger structure like a walkway or a platform.
This type of innovation had never been discovered so early in time.
"They are locking something in. So it restricts the movement and that's intentional. And nothing has been seen like that the archaeological record at this time and really they won't be seen again until maybe 9,000 years later, so a huge gape in time between what these people could do 477,000 years ago and then when we see that again in the archaeological record, in this case in the European record," says Barham.
"So that's how I understand it, so this a framework on which things could then be added, like a platform."
The log structure was made at least 476,000 years ago, that places the materials in a time before our species, Homo sapiens, evolved.
They would have been made by another kind of early human cousin — possibly Homo heidelbergensis, which was around in Africa at the time, authors said.
It suggests that these Stone Age people could have been more advanced than previously thought.
"It's what I call a disruptive discovery. I never expected it. And it took me a while before I appreciated what we were looking at. It didn't look very nice, to be honest. But it is much more complex than I thought and it suggests to me that early humans, early hominins before us, were actually capable of doing things which we would marvel at if we were doing it ourselves. So it's not just the stone tools, it's the wood as well. They've got this repertoire of materials now. They can transform their environment. They can build things that are lasting. That's new," says Barham.
It was previously thought that these people were hunter gatherers who moved from place to place, never staying at one site for very long.
But the simple structure shows they put down roots.
"Usually when you stay at a site for one or two days, you don't really do much with that site as such. You bring your tent along if you have one, or you make a small brush hut and that's it," explains Dirk Leder, an archaeologist for the Lower Saxony State Office for Cultural Heritage who was not involved in the study.
"While here, when you invest in the site or into the furniture, of the site if you like, all of a sudden we have a glimpse into more time investment. So people might have either stayed longer at this site than we expected or they might have been at the site very, very frequently, so repeatedly. And this sort of changes, at least for this time and space, our perspective on hunter gatherer groups half a million years ago in southern central Africa."
Just a few bits of wood could change how we view our ancient cousins.