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Swords, Cutting and Military History

Forensics: Weapon-related trauma on Seiyokan cranial remains, Kamakura

Forensics:  Weapon-related trauma on Seiyokan cranial remains, Kamakura

Artist unknown 1880

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Based on a paper by Drs. Tomohito Nagaoka, Kazuhiro Uzawa, Kazuaki Hirata, Evidence for weapon-related traumas in medieval Japan:observations of the human crania from Seiyokan, we’ll look at their work in conducting forensic examinations of remains from the Seiyokan site at Kamakura, Japan.  Kamakura was the defacto capital of the Kamakura Shogunate (1192–1333).

This city and its environs were destroyed in a series of battles in 1333, culminating in the total destruction of the ruling Hojo clan.

The researchers examined 91 sets of remains recovered from this site, six of which exhibited cut marks;  five male, one female.  These six remains were skulls only, recovered from a “cranial mass grave”;  a grave in which only heads were found.  The assumption was made that these remains were the decapitated heads of warriors or important persons, traditionally brought in by samurai as proof of their deeds.

As set out by the authors, the purpose of the study was:

…to examine the human crania from the archeological site at Seiyokan, to analyze the presence, distribution, and variability of their weapon related traumas, and finally to better understand violence in medieval Japan from osteological evidence.

in a previous post, the focus of the study was on visible impacts and fractures of the victim’s skeletons simply because there was no soft tissue to analyze.

Photographs of cut marks

Figure 2. Cut mark types. (a) Anterior view of the gash on the frontal bone. (b) Lateral view of the gash on the right parietal bone. (c) Lateral view of the gash on the right parietal and occipital bones. (d) Posterior view of the incision on the occipital bone. (e) Lateral view of the scratches on the left parietal

History and research background
The paper’s authors start off with a very short review of the history of the Kamakura Shogunate, followed by a discussion on the rising level of violence in this society, as documented by other researchers and their findings (check paper for references and cites).  They then use this information to help justify the need for their research:

Although several reports on traumas have been published, the osteological evidence for weapon-related traumas is often anecdotal and diagnosis is subject to the observer’s experience. Peri-mortem traumatic lesions without the formation of new bone callus are often difficult to distinguish from post-mortem damage caused by site-formation processes or post-recovery damage from excavation and curation (Walker, 2001), and the patterns of cut marks vary according to social context (Boylston, 2000). The study of weapon-related traumas, therefore, requires standards to distinguish human-induced traumas and their population specific interpretation. The purposes of this study are to describe the macroscopic and microscopic morphology of cut marks observed on human skeletons from the archeological site of Seiyokan in medieval Japan, to examine their presence, distribution, and variability, and finally to better understand violence in medieval Japan from osteological evidence.


Analytic methodology

In recording analyzing the remains and the types of cut marks found, they used a system invented by Dr. Suzuki, in which marks were divided into classes of cuts:

  • Gashes: Cuts which penetrate the skull, leaving a large “V”-shaped cut, likely caused by a sword.  To show why they use this definition, rather than the more standard forensic term “chop mark” they explain:  “When the cutting edge penetrated the soft tissue and reached the bone, it caused hacking damage on the contact area followed by a slicing motion of the edge. Therefore, chopping and slicing actions occur consecutively in a single blow of the sword. This characteristic handling of the cutting artifacts may cause bone modification which shows both dynamic and static loading of the cutting tools. Accordingly we classify cut marks in terms of their depth as well as their outline morphology in order to determine their cause more closely.”
  • Incisions: Long, slicing cuts which penetrate the exterior surface of the cranium, but not the interior.
  • Scratches: Short, non-penetrating grooves which leave marks but do not actually penetrate the cranial surface material

The location of the marks on each skull  were also recorded.


The remains and where they were found

As previously mentioned, six sets of cranial remains were examined, one of which was female.  As there were no skeletons to examine, the researchers focused on a detailed examination of the skulls.  The following chart (click to enlarge) shows the six sets of remains and where the cut marks were found:


Table 1. List of the Seiyokan crania with sharp force traumas
Click to enlarge

In summary, the authors a total of 16 lethal gashes on the six skulls, with one skull bearing nine cuts and another skull four;  a serious level of overkill suggesting either the victims died in the midst of heavy combat — perhaps  vs. multiple opponents — or the heads were disfigured after death.   All other remains bore a single cut mark.

The number of cut marks on the six individuals is 17.  They are all characterized by a linear, flat, clearly edged, and polished cut surface, which are consistent with the features of cut marks made by sharp steel blades. One is an incision which is restricted to the outer table and is characterized by a polished cut surface (5.9% out of 17 cut marks), whereas 16 are gashes which penetrate to both the external and internal laminae (94.1% out of 17). The former produces a unilateral flaking of cut marked surfaces and exhibits an asymmetrically elliptical shape from a superior view (Figure 2d). The latter, on the other hand, often enter into the cranial cavity, which is indicative of lethal trauma (Figure 2a–c). Neither the incision nor the gashes exhibit a color difference between the walls of the grooves and the original bone surfaces. The absence of healing traits from the injuries indicates that they were cut either immediately prior to death or in the post-mortem period. Although the cut marks appear predominantly on the parietal bones, the Seiyokan samples exhibit injuries not only on the frontal, parietal, temporal, and occipital bones but also on the zygomatic, nasal, and maxillary bones (Table 1, Table 4).


Comparing remains from various known battle burial sites

In an interesting section, the authors discuss the results of forensic investigation of other mass graves in the Kamakura region.  This shows, for example, that the site known as Zaimokuza had the largest number of remains with cut marks found, percentage-wise the site this paper is analyzing contained the largest number of fatal gashes.  Several charts allow easy comparison of the number of remains found at each site, the number of “cranial graves”, and the numbers of each type of cut mark found at each site.

Comparison of cut marks between sites

Click to enlarge


Notes on cut marks and other trauma

The work of previous researchers at other sites had shown a predominance for cut marks on skulls to be on either the left or right hand sides (parietal bones).  While this was found to be true for this study, the data collected by this paper’s researchers found cuts on the facial bones as well, which was somewhat unusual.

One skull bore what appeared to be a well healed, depressed area of cranial surface, with many fine scratches.  The authors conducted a series of in-depth investigations, recorded in the paper, and conclude it is very likely this person has had part of their scalp removed at some time, possibly as a judicial punishment, disfiguration by mutilation having been known to be practiced at the time period the remains came from.



The authors summarize very generally, noting that their research confirms and agrees with the findings of previous researchers at other sites, with several notes on the high level of violence found noted as historically practiced on members of both sexes during this violent and tumultuous period of Japanese history.



Evidence for weapon-related traumas in medieval Japan:observations of the human crania from Seiyokan: Tomohito Nagaoka; Kazuhiro Uzawa; Kazuaki Hirata:  Anthropological Science Vol. 118(2), 129–140 (2010)

Demographic and pathological characteristics of the medieval Japanese: new evidence from human skeletons from Kamakura, Japan: Tomohito Nagaoka;  Junmei Sawada; Kazuaki Hirata: Anthropological Science Vol. 121(3), 203–216, 2013


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