As if the Easter Island statues weren’t enigmatic enough, a few of them are wearing hats—6.5-foot-wide, 13-ton cylinders of cindery red volcanic rock called scoria. The hats are as much an enigma as the statues themselves. For starters, archaeologists aren’t actually sure they’re supposed to be hats at all.

Their shape—ranging from a straight-sided cylinder to a tapering cone, with a smaller cylinder on top—is similar to a style of woven grass hat that some historians say was once popular in New Caledonia. Carvings found on some statues in Hawai’i could represent similar hats, if you look at them from the right angle. But that same general shape could also represent a traditional Polynesian hairstyle for men of high rank: long hair bound up in a topknot, called a pukao, which is what gives the hats their name.

Archaeologists still aren’t sure which version, hair or hat, the statues’ builders intended, or why fewer than a hundred of the island’s several hundred statues, called moai, seem to have been visited by a giant milliner. The hats, or topknots, could be a sign that some statues (or the people, spirits, or gods they represented) were a much bigger deal in Rapanui religious life than others. Maybe the ones with the red hats are just prehistoric Linux fans.