NEW YORK (AP) — Researchers have uncovered a simple structure from the Stone Age that may be the oldest evidence yet of early humans building with wood.

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.

“It took me a while before I appreciated what we were looking at,” said study author Larry Barham, an archaeologist at the University of Liverpool. “It didn’t look very nice, to be honest. But it is much more complex than I thought.”