The most common symbolic use of the skull is as a representation of death and mortality, but such a reading varies with changing cultural contexts.
Humans can often recognize the buried fragments of an only partially revealed cranium even when other bones may look like shards of stone. The human brain has a specific region for recognizing faces, and is so attuned to finding them that it can see faces in a few dots and lines or punctuation marks; the human brain cannot separate the image of the human skull from the familiar human face. Because of this, both the death of, and the now past life of the skull are symbolized.
Moreover, a human skull with its large eye sockets displays a degree of neoteny, which humans often find visually appealing—yet a skull is also obviously dead. As such, human skulls often have a greater visual appeal than the other bones of the human skeleton, and can fascinate even as they repel. Our present society predominantly associates skulls with death and evil. However, to some ancient societies it is believed to have had the opposite association, where objects like crystal skulls represent "life": the honoring of humanity in the flesh and the embodiment of consciousness.