Factual error: During the big sacrifice scene an eclipse happens. An eclipse occurs when the moon passes between the earth and the sun. Later, apparently that night, the night mood is set by a shot of a full moon. The moon cannot be full until fourteen days after an eclipse, when it is directly opposite the sun.
Continuity mistake: At the first few scenes of the film the Indians are shown with dark, broken and corroded teeth. Halfway through the movie the main cast show pearly white teeth.
Continuity mistake: When Jaguar Paw is being chased through the jungle, there is one scene at night. He stops to rest, and turns his head to see the torches behind him. In the two close-ups of his face, the piercing in his lower lip is gone. It reappears as he turns head away from the torches and starts running again.
Continuity mistake: When the group encounters the little girl who foresees the future, the scars on her face move from shot to shot as dialogue takes place. In this same scene her face goes several times from very dirty to somewhat dirty.
Revealing mistake: Watch closely when the first two 'slaves' run for their freedom amidst flying spears. When Jaguar Paw's friend (the chunky fellow) gets speared, it is a 'through the armpit' effect. When he's gasping for breath in the next shot, the entry of the spear is actually more in the middle of his chest.
Visible crew/equipment: When the hunters have returned to the village, and Blunted is being pushed by his mother-in-law, at one point she is behind him, trying to push him forward. In the same shot, to the right of the screen, you can see a white hand touching his stomach as if telling him to stay put. When the angle changes, there is no one in front of him.
Continuity mistake: When Blunted is soaking his penis in the water container, the old medicine man with an "x" on his forehead is running towards him from the jungle. In the next shot he has his arm wrapped around another Indian laughing. There are also several children in front of the medicine man when there were no other Indians around him other than the man he was embracing.
Factual error: Given they seem to be so close (it takes him less than two days to get home) and so aggressive, it seems unlikely that Jaguar Paw's people have no knowledge of the existence of the Mayan city. Maya settlements at that time were widespread, with communities scattered widely around a political center.