A new study that examined the collections of major American and European museums found that male specimens outnumbered female specimens across most ancient and modern mammals with the exception of bats, anteaters, and sloths.

There is an important and ongoing conversation in the art world about the underrepresentation of women in museum and gallery exhibitions, but it’s a discussion that has always been anthropocentric. A new study has found that gender bias in favor of males extends to fossil and museum collections of mammals.

A team of researchers, led by Graham Gower from the University of Copenhagen, Denmark, examined two types of collections: museum collections of ancient modern mammals; and a sample of brown bear and bison fossils from the Pleistocene era (a geological epoch that began 1.8 million years ago and ended about 10,000 years ago).

For the first category, the scientists sampled the collections of the American Museum of Natural History, the Natural History Museum in London, the Smithsonian Institution National Museum of Natural History, and the Royal Ontario Museum. There they found that male specimens outnumbered female specimens across most ancient and modern mammalian orders with the exception of bats, anteaters, and sloths, which are mostly female.

In examining the Pleistocene mammals, the researchers used ancient DNA to genetically determine the sex of 186 bison and 91 brown bear fossils (the sex of modern fossils was identified by their genitalia). Their findings show that about 75% of the bison and 64% of the bear fossils were male. These results do not match the makeup of the natural world, where many mammalian species have a 1:1 sex ratio at birth, the researchers said.

The researchers suggest a few explanations for this bias. One is that male specimens are possibly easier to fossilize by virtue of their larger size. Another hypothesis says that male mammals tend to travel long distances and are more likely to live alone, which means their bodies can be found in more locations. A third possible explanation relates to human behavior. Many mammal specimens are donated to museums by hunters, who are more likely to target males because of their larger size, their decorative horns and manes meant to attract mates, or to avoid killing mothers that need to care for their newborns.