These logs could be the earliest known wooden structure

Stacked timbers dated to roughly 476,000 years ago show that ancient hominins worked with wood

Some 500,000 years ago in central Africa, ancient human relatives chopped down trees and transformed the wood into digging tools, wedges and what might just be the world’s earliest-known wooden structure.

Now, remnants of this ancient woodworking have been found at an archaeological site in Zambia called Kalambo Falls. Researchers can’t definitively identify the possible structure, which might have been a raised platform, a shelter or something else entirely. Whatever it was, it pre-dates the evolution of Homo sapiens by more than 100,000 years, hinting that hominins that lived long before our own species were already working wood.

Wood tends to decay quickly in the ground. If it was preserved at archaeological sites as faithfully as materials such as stone or bone, “we would probably use the term wood age rather than stone age”, says archaeologist Larry Barham at the University of Liverpool, UK. He and his colleagues describe the finds in Nature1 on 20 September.

An unexpected discovery

When Kalambo Falls was first excavated in the 1950s and 1960s, British archaeologist J. Desmond Clark and his team found stone tools and wooden objects that might have been tools, as well as a large wooden object interpreted as being part of a structure. But it was hard to tell the wooden objects’ age or whether hominins had made them.

Barham and his team started visiting Kalambo Falls in the early 2000s to date the site using modern techniques, and to hunt for more stone tools. “We didn’t expect to find wood,” Barham says.

But on the first day of a 2019 excavation, the researchers slid down a slope to the shores of the Kalambo River and noticed a piece of wood jutting out of a cliff face. Excavations of the waterlogged site turned up several pieces of wood that seemed to have been modified, as well as one big surprise: a 1.4-metre-long log that had tapered ends and a deeply carved notch where it rested on another large piece of wood.

Many of the wooden objects harboured signs of intentional modification, such as scrape marks, that resembled those on wooden artefacts from other waterlogged sites used by Homo sapiens, and on wooden items that the researchers made themselves using pre-industrial techniques. One of the small objects looked as if it could be for digging; another might have been a wedge.

The two large objects befuddled Barham until he got his hands on US building toys called Lincoln Logs. These are notched at the ends, allowing two pieces to be securely stacked perpendicular to one another. The notch on the Kalambo log could serve the same purpose, Barham says. “They were building something which was ― at least in one direction ― stable.”

Woodworking wonder

Barham wonders whether the wood was used to make a platform for fishing or to keep things off the muddy forest floor, some kind of raised track or even a simple shelter. Without further wooden material from the site, it’s really anybody’s guess, he says. “Madness lies that way.”

A technique called luminescence dating suggests that the large wooden objects are at least 476,000 years old, and some of the smaller tools are slightly younger. No hominin remains have been found at Kalambo Falls, but a 300,000-year-old skull from another Zambian site has been identified as Homo heidelbergensis, a possible common ancestor of Homo sapiens and Neanderthals (Homo neanderthalensis).

Andy Herries, an archaeologist at La Trobe University in Melbourne, Australia, isn’t surprised by the idea that hominins at Kalambo Falls made tools, and possibly structures, out of wood. Around this time, stone tools from Africa and elsewhere in the world show evidence of having been attached, or hafted, to wood, he notes. Hopefully, further excavations at Kalambo Falls can provide stronger evidence of how human relatives there were using wood.

Richard Roberts, an archaeological scientist at the University of Wollongong in Australia, is convinced by the dating. The wooden objects are intriguing, he says, and raise the possibility that wood use by hominins has been underappreciated because wood is so rarely preserved. (Nature/AP)