But according to one theory, the story of Santa and his flying reindeer can be traced to an unlikely source: hallucinogenic or "magic" mushrooms.
"Santa is a modern counterpart of a shaman, who consumed mind-altering plants and fungi to commune with the spirit world," said John Rush, an anthropologist and instructor at Sierra College in Rocklin, Calif.
According to the theory, the legend of Santa derives from shamans in the Siberian and Arctic regions who dropped into locals' teepeelike homes with a bag full of hallucinatory mushrooms as presents in late December, Rush said.
"As the story goes, up until a few hundred years ago these practicing shamans or priests connected to the older traditions would collect Amanita muscaria (the Holy Mushroom), dry them, and then give them as gifts on the winter solstice," Rush told LiveScience. "Because snow is usually blocking doors, there was an opening in the roof through which people entered and exited, thus the chimney story."
But that's just the beginning of the symbolic connections between the Amanita muscaria mushroom and the iconography of Christmas, according to several historians and ethnomycologists, or people who study the influence fungi has had on human societies. Of course, not all scientists agree that the Santa story is tied to a hallucinogen. [Tales of Magic Mushrooms & Other Hallucinogens]
Presents under the tree
In his book "Mushrooms and Mankind" (The Book Tree, 2003) the late author James Arthur points out that Amanita muscaria, also known as fly agaric, lives throughout the Northern Hemisphere under conifers and birch trees, with which the fungi —which is deep red with white flecks — has a symbiotic relationship. This partially explains the practice of the Christmas tree, and the placement of bright red-and-white presents underneath, which look like Amanita mushrooms, he wrote.
"Why do people bring pine trees into their houses at the Winter Solstice, placing brightly colored (red and white) packages under their boughs, as gifts to show their love for each other … ?" he wrote. "It is because, underneath the pine bough is the exact location where one would find this 'Most Sacred' substance, the Amanita muscaria, in the wild."
Reindeer are common in Siberia, and seek out these hallucinogenic fungi, as the area's human inhabitants have been known to do. Donald Pfister, a biologist who studies fungi at Harvard University, suggests that Siberian tribesmen who ingested fly agaric may have hallucinated into thinking that reindeer were flying.
"At first glance, one thinks it's ridiculous, but it's not," said Carl Ruck, a professor of classics at Boston University. "Whoever heard of reindeer flying? I think it's becoming general knowledge that Santa is taking a 'trip' with his reindeer," Ruck said. [6 Surprising Facts About Reindeer]
"Amongst the Siberian shamans, you have an animal spirit you can journey with in your vision quest," Ruck continued. " And reindeer are common and familiar to people in eastern Siberia. They also have a tradition of dressing up like the [mushroom] … they dress up in red suits with white spots."
Ornaments shaped like Amanita mushrooms and other depictions of the fungi are also prevalent in Christmas decorations throughout the world, particularly in Scandinavia and northern Europe, Pfister points out. That said, Pfister made it clear that the connection between modern-day Christmas and the ancestral practice of eating mushrooms is a coincidence, and he doesn't know about any direct link.
Many of these traditions were merged or projected upon Saint Nicholas, a fourth-century saint who was known for his generosity, as the story goes.
The Santa connection
There is little debate about the consumption of mushrooms by Arctic and Siberian tribes' people and shamans, but the connection to Christmas traditions is more tenuous, or "mysterious," as Ruck put it.
Many of the modern details of the modern-day American Santa Claus come from "A Visit from St. Nicholas" (which later became famous as "'Twas the Night Before Christmas"), an 1823 poem credited to Clement Clarke Moore, an aristocratic academic who lived in New York City.
The origins of Moore's vision are unclear, although Arthur, Rush and Ruck all think he probably drew from northern Europe motifs that derive from Siberian or Arctic shamanic traditions. At the very least, Arthur wrote, Santa's sleigh and reindeer are references back to various related Northern European mythology. For example, the Norse god Thor (known in German as "Donner") flew in a chariot drawn by two goats, which have been replaced in the modern retelling by Santa's reindeer, Arthur wrote.
Ruck points to Rudolf as another example of the mushroom imagery resurfacing: his nose looks exactly like a red mushroom, he said. "It's amazing that a reindeer with a red-mushroom nose is at the head, leading the others."
Other historians were unaware of a connection between Santa and shamans or magic mushrooms, including Stephen Nissenbaum, who wrote a book about the origins of Christmas traditions, and Penne Restad, at the University of Texas.
One historian, Ronald Hutton, told NPR that the theory of a mushroom-Santa connection is off-base. "If you look at the evidence of Siberian shamanism, which I've done," Hutton said, "you find that shamans didn't travel by sleigh, didn't usually deal with reindeer spirits, very rarely took the mushrooms to get trances, didn't have red-and-white clothes." But Rush and Ruck say these statements are incorrect; shamans did deal with reindeer spirits, and the depiction of their clothes' coloring has more to do with the colors of the mushroom than the shamans' actual garb. As for sleighs, the point isn't the exact mode of travel, but that the "trip" involves transportation to a different, celestial realm, Rush said.
"People who know about shamanism accept this story," Ruck said. "Is there any other reason that Santa lives in the North Pole? It is a tradition that can be traced back to Siberia."