Archeologists working in Guam in 1990 unearthed barbed spear points in two burials during excavations at a cemetery that was part of a Chamorro village site, dating to the Latte Period (AD 1000 to AD 1521). They found evidence that the Chamorros obtained the necessary bones from select portions of decomposed bodies.
According to Judith McNeil, senior archaeologist at the International Archaeological Research Institute, the Chamorro used the arm and leg bones from their own dead, as well as bones from the bodies of Spaniards and missionaries they killed. From the Apotguan site they found 11 spear tips made from human bones: five made from the tibia, two from the fibula, one from the humerus, one from the radius, and two others made from bones they weren’t sure of.
Father Peter Coomans, a Jesuit missionary in the 1670s, described the gory process by which Chamorro would extract the bones from the decomposed bodies:
To make the former, they despoil corpses of their leg bones, and the longer ones are the most desirable ones. For instance, should they want to get their hands on longer leg bones, they bury the corpses of the dead at a suite, so that the earth would hardly cover the legs from the hips down to the heels, to which they tie small cords, so that, when the ligaments have already putrefied, they pull them [i.e., the leg bones] out and intact from the rest of the body.
Other historic sources say that Chamorro people believed that the bones of their ancestors had supernatural powers. So these spear points may have served a ritual purpose as well as a practical purpose as weapons.
McNeil, Judith. (2002). Human spear points and speared humans: the procurement, manufacture and use of bone implements in prehistoric Guam. Bulletin of the Indo-Pacific Prehistory Association. Retrieved on January 24, 2014 from: http://journals.lib.washington.edu/index.php/BIPPA/article/viewFile/11818/10446 (This sources is missing a few pages had trouble find the complete PDF.)
Tolentino, Dominica. (2012 June 18). Ancient Chamorro Use of Human Bones. Guampedia. Retrieved on January 24, 2014 from: http://guampedia.com/ancient-chamorros-use-of-human-bones/