(Learn about the human digestive system.)
Scientists studied samples under a microscope and identified six different species of moss.
One species, Sphagnum imbricatum—commonly known as bog moss—was a huge surprise.
"It was a complete shock to find this because it doesn't grow anywhere close to where he was found," Dickson said.
The nearest location in Ötzi's day was a lowland marshy area around 12 miles (20 kilometers) south of where he was found.
Dickson and colleagues speculate that Ötzi used this highly absorbent moss to staunch the bleeding from a deep cut in the palm of his right hand.
"Sphagnum moss is well known to have antibiotic properties," said Jacqui Wood, an independent experimental archaeologist based in the U.K.
One of the mosses also revealed Ötzi's likely water sources, which were probably streams or caves.
Hymenostylium recurvirostrum only grows in moist environments on chalk or limestone rock.
"He probably ingested this in his drinking water," Dickson said.
Neckera complanata, a fan moss, also gave clues to his diet.
"The most probable explanation for this moss is that it was used to wrap the red deer and alpine ibex [a type of mountain goat] meat that he was carrying. When he ate the meat he also ate a little of the moss," Dickson said.
Allan Hall, an archaeobotanist from York University who wasn't involved with the study, agrees.
"These explanations are entirely plausible," he said.
Together with pollen and cereals found in his gut, the moss is helping scientists piece together the route that Ötzi took in his last days of life.
They now know that he came from high in the mountains, then went down to the lowlands—where he picked up the bog moss—then returned to the highlands, covering a distance of at least 37 miles (60 kilometers) in two or three days.
Despite his relatively advanced age for the time, he was a very fit man and obviously used to going up and down hills, experts say.
"His equivalent [physique] today might be a middleweight Olympic wrestler," Dickson said.
(Related: "Iceman Wore Cattle, Sheep Hides; May Have Been a Herder" [August 21, 2008].)
Ancient Toilet Paper
Evidence from other Neolithic sites, such as Swiss and German lake villages, suggests mosses were used for a variety of purposes.
Fan mosses are very springy and were often used as bedding or to stuff cracks in walls.
The plants are also found in ancient cesspits, and are thought to have been used as a primitive form of toilet paper.
Bog moss, meanwhile, was used as a wound dressing until World War II.
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