A "Heady" Burial Practice in Prehispanic Philippines
The Prehispanic Philippines was a colorful era for burial practices, and among these practices, separating the head from the body was one of them. It's known as a "head cult" (according to William Henry Scott) in which skulls were interred separately from their bodies. During this time skull boxes were quite common, and in some cases there were coffins with two extra skulls, or a skull at the feet instead of where the head should normally be.
There were jars that contained one or more skulls, or a skull inside and the rest of the body outside, or sometimes the skull was in a Celadon bowl on a niche overlooking the sea (wow, how calming).
This is not an evidence of head hunting because the heads were cut off with "surgical precision." After all, if you were a head hunter you'd just slice off the head, right? Also, "artificial skull deformation" was a common practice. Imagine a bulging skull with a high sloping forehead. It was practiced in parts of Southern Luzon, Visayas, and parts of Mindanao.
In Palawan, some skulls that were collected were soaked in red dye, which might possibly be hematite -- iron oxide. This was done in between the primary burial (a simple interment) and the secondary burial ("re-interment of the bones after remains of an earlier burial have successfully decomposed"), and sometimes called "bone-washing," which was observed in some other groups (ex: Ifugaos and the Sulod group from Panay).
"Bone-washing" is the process of cleaning and/or decorating the bones.
Notes taken from William Henry Scott's Prehispanic Source Materials: For the Study of Philippine History, pages 24-27.