During the Middle Ages, people ventured into the cave now called Einhornhohle to collect unicorn bones. It’s tempting to wonder whether those medieval cryptid hunters would be disappointed or fascinated to learn that the bones they unearthed from the cave actually belonged to ancient bison, deer, cave lions, bears, and other animals that died 50,000 years ago. Archaeologists began excavating the cave in 2017, and while cleaning and sorting their trove of non-unicorn bones, they discovered the handiwork of a long-dead Neanderthal artisan.

Around 51,000 years ago, someone carved a geometric design into the second phalanx, or toe bone, of a giant deer. The carver was almost certainly a Neanderthal, based on the bone’s radiocarbon-dated age, because no one but Neanderthals lived in Europe until around 45,000 years ago. As archaeologist Dirk Leder of the Lower Saxony State Service for Cultural Heritage and his colleagues put it, Einhornhohle is “situated along the northern boundary of the world known to be inhabited by Neanderthals,” in the Harz Mountains of northern Germany.

Three parallel lines cut diagonally across the surface of the bone. Another of set of parallel lines cross the first three at a more-or-less right angle; the carver was a few degrees off, but that’s still respectably precise for someone eyeballing their measurements and working with a flint blade. At the base of the bone (the end closer to the leg), the carver added four short lines, roughly parallel but not lined up quite as precisely as the others. Leder and his colleagues describe the resulting pattern as “offset chevrons.”

Neanderthal arts and crafts

Whatever you call the geometric design, carving it would have taken planning, effort, and a good supply of small, sharp flint blades. Leder and his colleagues can vouch for that because they tried it themselves, using cow phalanges and hand-knapped blades of Baltic flint, the stone a north German Neanderthal bone-carver would most likely have had access to. They examined the carvings under a microscope, looking for tiny tool marks that could reveal how the carver’s blade moved across the bone surface to create each line. Then they tried to replicate what they saw.

Each line in the relatively simple pattern took several steps—and about 10 minutes—to carve. The whole pattern represents about 1.5 hours of work, not counting preparation time. If you want to create your own Neanderthal bone art, here are step-by-step instructions:

First, boil the bone. Leder and his colleagues found that boiled bone was soft enough to carve without cracking and clean enough to firmly grip. Now, hold the edge of your blade vertically and cut across the bone with a sawing motion, which should etch the beginnings of a line into the surface. Next, hold the blade horizontally against the bone and scrape the surface, moving toward the cut you just made. That makes a long, straight cut with one steep side and one wide, shallow side. Repeat those steps in order until the engraving is about 2 mm deep. Then do the same thing nine more times.

Be prepared to replace your blade every five minutes or so. “Two blades were used to make each incision, as their edges became dull within just a few minutes,” wrote Leder and his colleagues. You’ll need at least 20 flint blades for this project, which means you’ll either need to make them yourself or convince someone with the right skills to make art supplies for you.

Summing all this up, the Neanderthal who etched this pattern into a deer bone 51,000 years ago wasn’t just making an idle doodle. This was a legitimate project; it took imagination to plan the design and figure out that a few individual lines would add up to a more complex pattern. It took resources and planning to assemble the tools, and it took time and effort to actually carve the pattern.