Altered records from around 476,000 years ago may be the earliest evidence of wooden structures, new research suggests.
Wooden artifacts rot easily and are relatively rare in the archaeological record compared to stone or bone artifacts. New findings published Sept. 20 in the journal Nature show that structural use of wood may date back to hominids, suggesting better cognitive abilities and a less nomadic lifestyle for some people than previously thought.
"It challenges preconceived notions of what complex and sophisticated behavior is," says archaeologist Larry Parham of the University of Liverpool in England. "It's a big evolution and changing landscape for me."
Man and his ancestors have used wood in one form or another for some time. The oldest known example of modified wood is a polished tablet from Israel, which is approximately 780,000 years old. Wooden tools do not appear in the historical record until about 400,000 years ago. Before this new study, the oldest known example of a wooden structure was even later: around 9000 BC.
During a 2019 excavation, Barham and his colleagues found five altered wooden objects on the open bank of a river flowing above Colombo Falls in Zambia. The area is rich in forests and has a constant high water table. This makes it ideal for human habitation, as the water absorbs oxygen from the submerged wood. Archaeologists have been excavating here since the 1950s using archaic methods, although the wooden objects cannot be precisely dated and are legible.
This time, the team used a technique known as luminescence dating ( SN: 07/19/17 ). Minerals buried underground slowly absorb background radiation in the form of battery charges, which can then be emitted as light. This indicates how many years have passed since the sample last saw the Sun. The team analyzed 16 sand samples, including those found directly around wooden objects, and divided the patterns into three time periods, from 476,000 years ago to 324,000 years ago.
In the sand, which is about half a million years old, the team found two large connected fragments with sharp edges and wide depressions where they overlap. Like the first version of the Lincoln log, it will hold the wood together. Both records contain evidence of cutting and scraping and were buried with scrap or carving tools, hand axes and other craft tools.
Researchers believe these logs may have been part of a structure (a causeway, woodshed, or seating area) that helped early humans manage their environment. Depending on the time and place, the building may have been built by a human ancestor, Homo heidelbergensis , who lived between 700,000 and 200,000 years ago. Other pieces of wood found at the site include a wedge, a drill rod, and a split log, dating from 390,000 to 324,000 years ago.
"This paper provides a fascinating look at our past," said Rebecca Berman Gorbus, a biological anthropologist at the University of Buffalo in New York who was not involved in the research. Other primates use wood and plants in different ways, he said. "So it's not surprising that [hominids] did it about half a million years ago."
Indeed, Barham doubts whether the Stone Age is an appropriate term for this period. “Let's assume that the archaeological record preserves wood like bone. "Perhaps we should call the Stone Age the Wood Age, or the Biotic Age, or something that reflects the general behavioral reality we see."
