Since cave art often depicts game species, a subject near and dear to hunters, most researchers have assumed that the people behind this mysterious artwork must have been male. But new research suggests that’s not right: when scientists looked closely at a sample of hand stencils, a common motif in cave art, they concluded that about three-quarters were actually drawn by women.

What they looked at, specifically, was the lengths of fingers in drawings from eight caves in France and Spain, National Geographic writes. Biologists established rules of thumb for general differences between men and women’s hand structure about a decade ago.

Women tend to have ring and index fingers of about the same length, whereas men’s ring fingers tend to be longer than their index fingers. Snow ran the numbers through an algorithm that he had created based on a reference set of hands from people of European descent who lived near his university. Using several measurements—such as the length of the fingers, the length of the hand, the ratio of ring to index finger, and the ratio of index finger to little finger—the algorithm could predict whether a given handprint was male or female. Because there is a lot of overlap between men and women, however, the algorithm wasn’t especially precise: It predicted the sex of Snow’s modern sample with about 60 percent accuracy.

The 32 hand prints he found in the caves, however, were more pronounced in their differences than those of the modern men and women he sampled. Based upon the model and measurements, he found that 75 percent of the hands belonged to women.

National Geographic points out that the mystery is far from definitively solved. While some hail the new study as a “landmark contribution,” others are more skeptical. Another researcher recently studied the palm-to-thumb ratio of the hand prints and concluded they mostly belonged to teenage boys, who, he told NatGeo, often drew their two favorite topics: big powerful animals and naked ladies.

More from Smithsonian.com:

The Top Four Candidates for Europe’s Oldest Works of Art

Is This the Oldest Cave Art on the Planet?