Thousands of miles away in Washington, Jane MacLaren Walsh keeps one of the skulls in her office at the Smithsonian Institution. She doubts the ancient Mayans ever had any such skulls.

An anthropologist and antiquities sleuth, she has spent more than a decade studying the best-known skulls, like the ones acquired by the British Museum and Paris' Quai Branly museum over a century ago, as well as the Smithsonian's own skull.

She says they are stylistically unlike pre-Hispanic depictions of death's heads, and often show microscopic marks from cutting tools unavailable in pre-Hispanic times.

"None of them is ancient," Walsh said. About the purported powers, she notes wryly: "I've been sitting in fairly close proximity to one of the skulls for about 16 years, and I have not witnessed anything like what people say."

The British Museum keeps a skull in its collections largely as a curiosity, listing its provenance as "probably European, 19th century."

It's possible that the near-human sized fakes may have been inspired by two real crystal skulls now on display at Mexico City's respected National Anthropology Museum. Much smaller and less perfectly carved than the ones held at the museums in Europe, these jewelry-sized trinkets, about an inch in height, are in the Aztec and Oaxaca collections, where the museum classifies them as either late pre-Hispanic or early colonial.

The skulls' legend has spawned a new breed of followers.

New-agers have associated the skulls with the belief that the Mayan "Long Count" calendar runs out on Dec. 21, 2012, when it reaches the end of a 5,126-year cycle. According to this theory, all 13 skulls must be reunited and lined up together to prevent the world from falling off its axis.

"I personally feel that (the skulls) are coming out now because humanity needs the information, their energy and they have probably their own purpose why they're coming out: to help us to create world peace," said Joshua "Illinois" Shapiro, 53, a self-described Crystal Skull Explorer who makes a living touring and giving lectures.

Shapiro has traveled the world seeking out skulls, and believes they link us to knowledge of past worlds like the Mayas, the lost civilization of Atlantis, or even extraterrestrials.

"I was wearing the Indiana Jones hat for a very long time," he says, "far before they ever thought about putting a crystal skull in an Indiana Jones movie."