Artificial Cranial Modification: Trephination

Trepanation 5
Image by Luciana Christante via Flickr

The practice of artificially modifying the human skull has been a part of human culture as far back as 45,000 years BP[1], and it has been shown to occur on every inhabited continent . Two primary forms of artificially modifying the human skull include trephination, the deliberate and surgical creation of a hole in the cranial vault, and the application of pressure on the crania of infants or toddlers to reshape the cranial vault from its natural form. Various hypotheses exist to explain the origins and reasons for these practices in human cultures in both the ancient and modern worlds, but none appear to be conclusive, though several do seem to be compelling when reviewed in the light of other archaeological and ethnographic data.


Trephination as a practice in prehistory was first noted by E. George Squier in 1865 but has been shown to exist in most inhabited regions of the world and in periods of human history and prehistory as far back as the Neolithic[2][3]. Trephining is the act of surgically perforating in the skull for perceived therapeutic purposes and the term is often used interchangeably with “trepanation,” however, Ortner makes an effort to differentiate between “trephination” and “trepanation.” The latter refers to the act of creating a perforation by use of an instrument. The former indicates that a section of bone is actually removed from the skull. The term “trepanation” is derived from the Greek term trypan, meaning “to pierce”.

Squier’s Incan skull is one that shows a scraping of the frontal bone in four regions such that a rectangular piece of bone was removed as a result (fig. 1). The instrument used was likely an obsidian or chert blade and the perforation exhibits no indication of healing so the patient very likely died during the procedure. The discovery of this skull created a sensation within the archaeological and historical community, the sentiment at the time creating an expectation that cranial surgery by “primitives” or “savages” would be a complex task far removed from their abilities. Squier’s example was a clear and indisputable example of human ingenuity, knowledge and understanding in the ancient world. It was an unmistakable, intentional modification of a human skull by human hands.

Squier’s discovery inspired and fascinated Paul Broca in France, who was fascinated not only with the idea of pre-Columbian Peruvians performing cranial surgery but with the reason for the surgery to begin with. Broca believed the act of trephination was one that was originally motivated by superstition and an appeasement of the supernatural which he based on observations of contemporary cultures that did so for these reasons.

No clear evidence for the casting out of evil spirits, demons, devils or other superstitious motivations appear to exist in the archaeological record to date and the idea remains an hypothesis, though one that may be intuitive given the superstitious nature that can exist among human culture as pointed out by Broca. The intuitiveness of the hypothesis is such that it appears in both academic and popular texts and writings. Ronald J. Comer, in his Abnormal Psychology, discusses the idea that South Americans (ostensibly the Inca) used trephination as a supernatural response to severe abnormal behaviors such as hallucinations or melancholia and he goes on to equate the practice to Western exorcisms.

Researchers have analyzed 66 skulls obtained from 11 Cuzco-region burials in Peru, which exhibited 109 trephinations in all[4]. Most of the methods of trephining these skulls included circular cutting and scraping. They discovered the survival rate among the individuals they analyzed to be 83% evidenced by the well-healed bone of most individuals, some of which exhibited multiple, well-healed trephinations. The key hypothesis Andrushko and Verano set out to test was that use of trephination as a medical treatment as opposed to cultural motivations. What they discovered was that great care was taken to promote healing and prevent infection.

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References and Notes:
  1. Trinkaus, Erik (1982). Artificial Cranial Deformation in the Shanidar 1 and 5 Neandertals. Current Anthropology, 23 (2), 198-199. []
  2. Andrushko, Valerie A. and Verano, John W. (2008). Prehistoric trepanation in the Cuzco region of Peru: a view into an ancient Andean practice. American Journal of Physical Anthropology, 137, 4-13. []
  3. Fernando, Hiram and Finger, Stanley (2002). “Ephraim George Squier’s Peruvian Skull and the Discovery of Cranial Trepanation.” In Trepanation: history, discovery, theory. Robert Arnott, Stanley Finger, Christopher Upham Murray Smith (eds.). Taylor and Francis. []
  4. Andrushko, Valerie A. and Verano, John W. (2008). Prehistoric trepanation in the Cuzco region of Peru: a view into an ancient Andean practice. American Journal of Physical Anthropology, 137, 4-13. []