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RESEARCH ARTICLE
Radiological and histological findings in
ancient salt mummies from the salt mine of
Douzlākh, Iran
Lena Maria O
¨hrstro
¨mID
1
*, Herman Marquez
1
, Roger Seiler
1
, Beata Bode
2
, Abolfazl Aali
3
,
Thomas Sto
¨llnerID
4,5
, Frank Jakobus Ru
¨hli
1
1Faculty of Medicine, Swiss Mummy Project, Institute of Evolutionary Medicine, University of Zurich, Zurich,
Switzerland, 2Institute of Pathology and Molecular Pathology, University Hospital Zurich, Zurich,
Switzerland, 3Archaeological Museum of Zanjān, Emaarate Zolfaghari, Zanjān, Iran, 4Ruhr Universita
¨t
Bochum, Institut fu¨r Archa
¨ologische Wissenschaften, Bochum, Germany, 5Deutsches Bergbau-Museum
Bochum, Research Department & Mining Archaeology Research Branch, Bochum, Germany
*lena.ohrstrom@iem.uzh.ch
Abstract
Computed tomography studies and histological analyses were performed on the mummified
remains found in the Chehrābād salt mine in northwestern Iran. The ancient salt mummies
are dated to the Achaemenid (550–330 BC) and Sassanid (3rd–7th century AD) time period
and died in mining incidents. The aim of the study was to describe the radiological and histo-
logical findings of several ancient Iranian salt mummies with special interest in pathological
and postmortem changes. The mummified remains show multiple traumatic alterations,
such as fractures and signs of massive compression. Histological analyses can clearly dif-
ferentiate soft tissue, however the preservation status is variable. These Iranian salt mum-
mies are a rare example of the ancient Iranian population. The soft tissue and organs are
well preserved, however in different degrees due to the varying conditions.
Introduction
Several ancient Iranian salt mummies and mummy-parts have been found in the Chehrābād
salt mine in northwestern Iran between 1993 and 2010. C14-dating revealed that they are
either dated to the Achaemenid (6
th
– 4
th
century BC) or the Parthian-Sassanian (2
nd
– 6
th
cen-
tury AD) time period [1–4]. In contrast to artificially embalmed mummies known from differ-
ent cultures, the Iranian Saltmen have been naturally mummified [5]. Different ways of
natural mummification may occur depending on climatic and environmental conditions. In
the case of the salt mummies the mummification process was induced by salt. As in the artifi-
cial mummification procedures in ancient Egypt, the preservation of soft tissue was mainly
caused by the hygroscopic effect of the salt [5]. The resulting dehydration inhibits bacterial
growth and arrests decomposition.
The Chehrābād Saltmen (SM) are of special archeological and historic interest. They are
rare examples of individuals dating to the ancient Persian periods and are, to date, the only
known preserved salt mummies worldwide [6].
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OPEN ACCESS
Citation: O
¨hrstro¨m LM, Marquez H, Seiler R, Bode
B, Aali A, Sto¨llner T, et al. (2021) Radiological and
histological findings in ancient salt mummies from
the salt mine of Douzlākh, Iran. PLoS ONE 16(4):
e0250745. https://doi.org/10.1371/journal.
pone.0250745
Editor: David Caramelli, University of Florence,
ITALY
Received: November 24, 2020
Accepted: April 12, 2021
Published: April 30, 2021
Copyright: ©2021 O
¨hrstro¨m et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: All relevant data are
within the manuscript.
Funding: The Salt Mine Exploration Project is a
multidisciplinary and international research project
including the Iranian authorities, represented by the
ICAR (Iranian Centre of Archaeological Research/
ICHTO), the Ruhr University of Bochum, Institute
for Archaeological Studies and the Deutsches
Bergbau-Museum Bochum as the main project
partner as well as further partners from Zurich,
Oxford, Paris, Besanc¸on, and Tehran. The fieldwork
The Archaeology of the Iranian Saltmen
The Chehrābād salt mine of Douzlākh is located 75km northwest of Zanjan city near the vil-
lage of Hamzelou in northwestern Iran. The mine is part of a large salt dome with an area of
ca. 20 hectare; 1350 meters above sea level, latitude N 36˚54’52’’, longitude E 47˚51’25’’ (Fig 1).
The rock includes red, green, and grey marl and clay deposits with gypsum, plaster and salt
fragments [4], pp. 17–18.
Mining at Chehrābād is an exceptional example of a salt mine that has been exploited dur-
ing several time periods. Due to the long-running mechanical excavation of salt, deposits of
this mineral have emerged from the underlying layers. Still active until recently, this salt
deposit was considered important in recent years, but also in ancient times. Evidence of salt
exploitation has been reported during four extended periods, the Achaemenid (6
th
– 4
th
cen-
tury BC) and Sassanid (3
rd
– 7
th
century AD) eras as well as the middle and late Islamic periods
(11th/12th. Century AD and 18th–20th century AD, respectively).
To date, the human remains of at least eight different individuals have been found at this
location and their descriptions are detailed in Aali et al [2].
When the first salt mummy was discovered, the salt mine was still active. Upon the discov-
ery of the remains of Salt Man #1 (SM1) in the winter of 1993, field work was conducted in the
Fig 1. Chehrābād salt mine; excavation site. Photo taken by Frank Ru¨hli.
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is financed by the DFG (DFG-Grant no: STO 458/
12). Further research projects of these project
partners receive financial support from the Ma¨xi-
Stiftung, Zurich, Switzerland and the Research
Laboratory of Arts and Humanities (University of
Oxford), UK The funders had no role in study
design, data collection and analysis, decision to
publish, or preparation of the manuscript.
Competing interests: The authors have declared
that no competing interests exist.
same year. At this location, salt extraction continued through 2004 until the remains of SM2
and SM3 were accidentally discovered. In the meantime, mining activities have ceased and the
site has been protected by Iranian Heritage laws since 2009. Since the discovery of human
remains as well as multiple artifacts, archaeological field work at the Chehrābād salt mine has
resumed.
With the support of the German Research Foundation (DFG), systematic excavations were
conducted in 2010–2017 by a multidisciplinary research team, led by the Iranian Cultural Her-
itage Centre Zanjān (Miras Farhangi Zanjān; Ruhr University of Bochum, Institute for
Archaeological Studies and the Deutsches Bergbau-Museum Bochum as the main project part-
ner, other collaborators from Tehran, Zurich, Oxford, Vienna, Paris and Besanc¸on) [4,7]. This
field and laboratory work discovered SM6 and assured the archaeological and stratigraphical
contextualization of the site. Several organic accessories such as fur and textile clothing as well
as working tools were excavated and display the rich material background of the ancient salt
mining communities [4,8,9].
The archaeological excavations have yielded exciting results on the technology and logistics
of the old mining processes [4] and there is evidence of at least three mining accidents.
Most of the Saltmen were likely miners and died in the mining accidents.
Material and methods
Material
Hitherto human remains of at least eight individuals have been found, dating either to the
Achaemenid or Parthian-Sassanian time period (Fig 2).
Fig 2. a-g: Photos of the salt mummies; a) SM1; b) SM2; c) SM3; d); thorax found nearby of SM1; e) SM5; f) SM6; g) leather shoe with lower leg,
likely belonging to SM1, SM7 or SMX. Photos taken by Frank Ru¨hli (e, f, g), Abolfazl Aali (b, c) and Lena O
¨hrstro¨m (a, d).
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SM1 was found during mining activities in 1993. A mummified head with long hair and a
beard is preserved with a gold earring in his left ear (Fig 2a). C-14 dating indicates that the
miner lived in the early Sassanian period (220–390 AD) [1,2]. In the subsequent rescue excava-
tion, a left lower leg inside a well-preserved leather boot was found nearby, eventually belong-
ing to the same individual (Fig 2g). Further mummified remains including cervical vertebrae
and a second maxilla were discovered in the same area and delivered to the excavators A.A.
Mir Fattah and H. Sobouti and then to the National Museum of Iran. It was determined from
these remains that there must be at least two individuals. Since these investigations took place
at a later date, the mummy is named SM7. Additional mummified remains also in context
with excavations around SM1, but with unclear circumstances of how these were found, are
stored in the archive of the National Museum of Iran in Tehran, including part of a thorax, a
humerus, and an ulna as well as some loose ribs (Fig 2d). These remains also belong to SM1,
SM7, or another individual. Molecular investigations to clarify any relationships are ongoing.
SM2 was found during mining activities in 2004 (see above). He is mostly skeletonized and
highly fragmentary; however, some soft tissue, including hair and a beard, are preserved
(Fig 2b). He is dated to the later Sassanid time period (430–570 AD). SM3 was also discovered
during mining activities in 2004. He was found under a large salt block and was heavily com-
pressed and mostly skeletonized. Fragmentary bones with some soft tissue remnants are pre-
served (Fig 2c). The remains were dated to the Achaemenid time period (410–385 BC) [1,2].
Further studies showed that these human remains probably belong to two different people.
Regardless, these remains were designated as SM8 [10].
No complete radiological analyses have been performed of SM2 or SM3, since they are
mostly fragmentary and skeletonized. SM4 (SM4) was found during the first excavation season
in 2004/5 and is the best preserved mummy. He was an adolescent of about 15 years and dated
to the Achaemenid time period [1,2,11]. The radiological findings of this individual have been
described separately [9]. SM5 was found during the second field season in 2005. The body had
been laying under a large rock, which was removed to excavate the mummy. SM5 is largely
skeletonized and the bones are almost fully preserved (Fig 2e). The head shows skin and hair
remnants and soft tissue is found on the arms, legs, and thorax. Additionally, a few fragements
of clothes are also preserved. Radiocarbon dating [2,4] assured the assignment to Achaemenid
time period (ETH (41106: 95.4% probability: 730BC (6.1%) 690BC; 550BC (89.3%) 380BC)).
Remains of SM6 consists of a cranium with multiple fractures (Fig 2f) and likely part of a pelvis
that was found nearby. He was excavated in 2010 [2,4]. The head was dated to the Sassanid
period (430–620 AD, ETH-41107).
While SM1 is on exhibit in the National Museum of Iran in Tehran, the other Saltmen are
currently exhibited in the Archaeological Museum of Zanjān, Zanjān, Iran.
Methods
Radiological analyses using X-ray were previously performed on SM1 and SM4 [3,11]. These
investigations are not discussed here. Due to the availability of improved imaging technologies,
the radiological analyses were repeated with Computed Tomography (CT).
New radiological investigations were performed at the Tehran Heart Center, on a clinical
Siemens Somatom Definition Flash CT-Scanner. Imaging parameters were as following;
512x512 matrix size, between 0,49 and 0,89um Pixel spacing, between 107 and 636 mA tube
current, between 0,6 and 1mm slice thickness and between 80 and 140 kv tube voltage. Radio-
logical analyses of SM4 and SM6 were performed separately in 2011 at the Pardis Nor Medical
Center in Tehran on a clinical CT scanner (Siemens Sensation 16) with the following imaging
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parameters (for SM6): 5mm slice thickness, 120kvP, 308mA tube current, 512x512 matrix size,
and 0,39um pixel spacing.
The datasets were processed with DICOM reading software (OsiriX MD v.8.0.1, Pixmeo,
Switzerland), including multi-planar reconstructions (MPR) and three-dimensional volume
rendering (3D VR).
Histological analyses were performed at the Institute of Pathology and Molecular Pathology
of the University Hospital, Zurich, Switzerland. The tissue samples were rehydrated and fixed
by immersion in buffered 4% formalin. Specimens containing bone were decalcified in EDTA.
All samples were embedded in paraffin. 2 μm thick sections were cut and all were stained with
hematoxylin and eosin (HE), elastica Van Gieson (EVG), PAS, Grocott and Gram stain
according to routine standard procedures. An overview of the samples is summarized in
Table 1.
Age estimation was performed by using the bone age status of the hand, feet and knee, the
dental status, as well as physical characteristics. Standard sex estimation in skeletal material is
based on the analyses of the pelvis bones [12]. While additional features, such as skull shape,
are also utilized additionally to standard sex determination methods, these features were found
to be too indeterminate to be used on their own [13]. Molecular sexing using ancient DNA
(aDNA) was applied for SM5.
Ethics statement: No permits by ethics committee were required for the described study,
since the investigated ancient human remains are older than 1500 years and no living relatives
are known. The investigations were done according to our code of ethics:
IEM Code of Ethics http://www.iem.uzh.ch/en/institute/iemcodeofethics.html.
The research institute of the cultural Heritage and Tourism of Iran (RICHT) granted per-
mission for the field research.
Results and discussion
All individuals show multiple traumatic lesions and postmortem alterations, including frac-
tures and compression-related lesions as well as shrunken tissue and organs. The traumatic
injuries are most likely the results of the various assumed collapses that occurred in the ancient
Table 1. Overview of the histology samples.
Salt mummy Sample region Tissue type Bacterias Fungi Sample number
1 throat collagen rich tissue (fascia?)/fatty tissue a lot probably 112
1 throat thick collagen bundles/fatty tissue (tendon?/fascia?) no a lot 106
1 throat collagen rich tissue/refractile materials (cristals) a lot few 107
1 hair hair/plant particles no no 104–2
1? left rib bone and periostal soft tissue little no 111
3 right tibia cortical bone no no 124
4 right arm pit skeletal muscle and fatty tissue no no 115
4 pubic symphysis cartilage and soft tissue some no 116
4 left pectoral muscle skelettal muscle/fatty tissue no no 117
4 left clavicle spongiosa bone no no 118
5 right femur cortical bone no no 121
6 right parietal bone bone (spongiosa and cortical) no no 123
unclear isolated maxilla bone no a few 102
unclear inner thorax unclear, only collagen fibers not tested not tested 3303
unclear vertebral/spinal unclear, only collagen fibers not tested not tested 3305
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salt mines. Similar fractures are found in modern victims of high velocity trauma or mining
accidents [14].
Histologically, various tissues, such as connective collagen fibers, adipocytes of the fatty tis-
sue, vascular tissue, and hair structure are well identifiable. However, bone tissue is best pre-
served. Several samples show a high bacterial load and presence of fungi, indicating
colonization, that most likely happened postmortem.
Salt Man #1 (SM1)
Radiological findings. The partially mummified head including the proximal cervical
spine (C1 to C3, and upper portion of C4) is preserved (Fig 3). The alignment is not intact, as
the vertebral bodies are moved to the side and tilted frontally. A distal fragment of the left clav-
icle bone is preserved, together with the acromion from the left scapula, although both frag-
ments are dislocated. The mummy wears a circular, metallic earring in the left ear. Hair and a
beard are also preserved. The frontal and maxillary sinus, as well as the ethmoidal cells,
together with the mastoid, are well-pneumatized. The cranial plates show no fractures. The
ethmoidal cells are fractured at several locations. The ramus of the right mandible is fractured
between the condylar process and the coronoid process, and also at its distal portion. The right
maxillary bone and the lateral wall of the orbit show multiple fractures. Only small portions of
the orbits remain. No anatomical structures can be identified within the orbits. Some dehy-
drated brain remnants are found fronto-parietally and parts of dura, falx, and tentorium are
preserved. Some remains of the spinal cord/spinal dura are observed in the spinal canal
(Fig 3b).
Dental status. While all teeth in the lower jaw are present, some of the molars in the
upper jaw are missing, the remaining root of 17 (after the FDI nomenclature) shows apical
translucency, ca. 4mm in diameter. Premolars and molars show extensive dental wear, i.e. the
occlusal surface is completely worn to the dentine, and in the case of 46 dental wear reaches
even the dental pulp. The other teeth have slight to moderate wear. There is an overall increase
in the distance between the cementoenamel junction and the alveolar crest, partially due to the
loss of dental hard tissue, but in the molar region of the lower jaw clearly because of chronic
periodontitis. Postmortem fracture only occurs in the crown of 25. In conclusion, although
there are no signs of caries, the molars and premolars are heavily compromised by dental wear
and periodontitis.
ba
Fig 3. a) axial slice and b) MPR reconstructions of the head of SM1. Stars: Shrunken brain remnants.; arrows: Dura
remnants; arrowhead: Spinal nerves and dura remnants. C: Dislocated clivus.
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Found in close proximity of SM1’s head was a partially mummified lower leg, including the
foot in a well-conserved leather boot. The foot, including the ankle, are fully mummified,
whereas the proximal lower leg is skeletonized. The knee joint is missing. No osseous patholo-
gies are observed. The epiphyseal plates are closed, indicating an adult age. The goat-leather
boot is very well preserved and partially filled with soil deposits, such as sand and probably
some stones. No socks were worn. The toes are in a flexed position with almost no space in
front of the toes, indicating the fit of the shoe was possibly a bit too short. The boot style is dif-
ferent than that worn by SM4; SM1 wore a tall shaft leather boot, while the shoes of SM4 are
ankle-high with a sole (Fig 4).
As described above, further contextual remains may belong to SM1 or possibly other addi-
tional individuals (e.g. SM7) [10]. These remains include part of a thorax with partially pre-
served vertebral column, a fragmented right scapula and shoulder, with preserved soft tissue
but no inner organs, humeral and ulnal bones as well as some loose fragmented ribs. Addition-
ally, three thoracic vertebrae with some dura remnants and a part of a maxillary bone with
teeth and very little soft tissue are preserved. The vertebrae and thorax may belong to SM1, but
the maxillary bone does not, as the skull has two intact maxillary bones. Instead, this fragment
likely belongs to another individual interred in the vicinity. The CT scan showed closed
Fig 4. Comparison of shoes for SM1 vs SM4. a) 3D volume rendering of the shoe of SM4, b) sagittal MPR, c) 3D
volume rendering of the lower leg of the assumed SM1, d) corresponding MPR. Note that no socks are worn.
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epiphyseal plates, indication an adult age, but no substantial degenerative changes. Some peri/
postmortem fractures are present, but no pathologies are evident. Thus far, these skeletal
remains have not been radiocarbon dated.
Histological findings. Several samples have been analyzed, including soft tissue from the
neck and throat, as well as hair and ribs. Fatty tissue including blood vessels as well as collagen
bundles could be identified in the throat region. Bone and periosteal soft tissue are visible and
the hair structure is still intact. An abundance of fungi and bacteria are identified particularly
in the throat region (Fig 5).
Histological analyses of the thorax found contextually separate only identified collagen
fibers. No tissue structure could be identified, probably due to a poor state of preservation
(Fig 6; 3303 and 3305).
Salt Man #2 (SM2)
No radiological analyses were performed on SM2. For the histological analyses, sample size
was too low.
Dental status. The following findings can be obtained from the available photos: Dental
wear lays the dentine free in patches on the occlusal surface of 15 and 16. There are multiple
Fig 5. Histology samples of SM1. Sample numbers 106 & 112: Throat area. Note the well-preserved collagen fibers on the HE stain of sample 106. The
Grocott stain shows multiple fungi (white arrow). 112: Note the collagen rich perivascular tissue (big arrow) and part of the tunica muscularis of an
artery (big arrow). 104–2: Hair. 107: Throat area, the gram stain indicates a high amount of gram positive bacteria (arrow). The polarized light stain
indicates crystalline birefringent substance mixed with the tissue. 111: Part of left rib, probably belonging to SM1 with bone (white arrow) and periostal
soft tissue (black arrow) with collagen fibers and fatty tissue. Histological staining HE: Hematoxylin and eosin. EVG: Elastica Van Gieson PAS: Periodic
acid-Schiff. Grocott: Silver stain for detection of fungi. Gram stain: For detection of bacteria.
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postmortem fractures present, (15, 13, 11, 21) and on the left side, teeth not preserved from 26
onwards. The periodontal status is normal and no carious lesions are visible.
Salt Man #3 (SM3)
No radiological analyses have been performed on SM3 because the remains are mostly skele-
tonized and highly fragmented.
Histological findings. A sample from the right tibia shows regularly structured mineral
matrix of normal ‘necrotic’ cortical bone (Fig 6; 124). No bacteria or fungi are identified.
Salt Man #4 (SM4)
Radiological findings are discussed elsewhere, as mentioned above.
Histological findings. Several samples of SM4 have been investigated, including soft tis-
sue from the armpit and left pectoral muscle as well as a bone sample from the clavicle and tis-
sue from the os pubis region. Skeletal muscle, fatty tissue, spongiosa and cartilage can be
Fig 6. Histology samples of SM3, SM5, SM6 and SMX. Bone samples from SM3, SM5 and SM6 showing normal
necrotic cortical bone matrix. Note the intact osteon structure (circle). Arrowhead: Haversian canal with remnants of
blood vessels. Arrow: Osteocyte lacuna. Samples 3305 and 3305 from the inner thorax of SMX, with unclear excavation
context, show collagen fibers without assignable tissue. Histological staining HE: Hematoxylin and eosin stain, EVG:
Elastica Van Gieson.
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visualized. No fungal structures were seen, however some bacteria were identified in the pubis
region (Fig 7).
Salt Man #5 (SM5)
The body of SM5 is almost fully preserved, however, it is mainly skeletonized and divided into
several parts. Missing parts of the skeleton include the lower thoracic vertebrae (T6 to T11),
the left scapula, the proximal portion of the humerus, and the right hip bone.
Radiological findings. The body shows multiple traumatic alterations, such as fractures
and signs of extreme compression. No intravitam pathological alterations were found on the
bones. The epiphyses of the hand, as well as the long bones are closed, indicating an adult age
estimation. According to the parameters proposed by Walker and Lovejoy [15], radiological
examination of the clavicle estimates the age range of this individual to be approximately 45–
49 years old. However, dental eruption patterns suggests a younger individual, which will be
discussed later.
The cranium shows no fractures. The clivus is dislocated and moved to a caudal position,
however the sella turcica remains intact. The maxillary, sphenoidal, and frontal sinuses and
mastoids are well-pneumatized. The cranial cavity shows some brain remnants in the frontal
region and parts of the dura. However, the cavity is largely filled with an isodense and compact
Fig 7. Histology samples of SM4. Sample number 115: arm pit with skeletal muscle (a) and fatty tissue (b) with adipocytes (arrow). 116: os pubis with
cartilage tissue (big arrow) and surrounding soft tissue with connective tissue (small arrow). 117: Pectoral muscle with skeletal muscle fibres (black arrow)
and fatty vacuoles (white arrow). 118: Clavicle bone with normal ‘necrotic’ spongiosa. Histological staining HE: Hematoxylin and eosin. EVG: Elastica Van
Gieson.
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structure, probably soil or salt and small stones (Fig 8a & 8b). The orbits show no fractures,
and are mainly filled with soil. The orbit contents are not preserved.
The thorax is heavily compressed, mainly on the left side, and the ribs have multiple frac-
tures on both sides. On the right side, seven proximal ribs are preserved and anatomically posi-
tioned; on the left side, five proximal ribs are preserved. Parts of the mediastinum can be seen,
but no thoracic organs can be clearly identified. Remnants of a hollow organ are observed
close to the beginning from the pharynx, dividing into two parts at the distal end, likely corre-
sponding to the trachea (Fig 8a & 8b).
All cervical vertebrae and thoracic vertebrae T1 to T5 are preserved and anatomically posi-
tioned. No fractures or degenerative changes are present in these vertebrae. The dens axis is
well-positioned, although the whole spine is slightly rotated to the right from T2 onwards. Ver-
tebrae T6 to T11 are missing. Lumbar vertebra, including T12 as well as the sacral bones, are
preserved. A slight decrease in the height of vertebral bodies L4 and L5 is noted as well as frac-
tures of some spinal processes. The sacrum is dislocated at S3-S4.
Fig 8. (SM5 & SM6). a) sagittal and b) axial MPR of SM5 showing the probable trachea remnants (arrows). c) axial
view and d) coronal MPR of the cranium of SM6. Arrows indicating fractures and disrupted sutures. Star: Soil.
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Several osteophyte formations and irregularities of the upper and bottom plates are found
(Fig 9a–9c). Some remnants of the spinal nerves are seen in the spinal canal in addition to
some soil.
Both clavicles and the sternum are intact and the sternoclavicular joints are preserved. The
right shoulder is preserved including the proximal part of the scapula and the entire humerus.
There is a small fracture at the inferior angle of the scapula. The right elbow is completely dis-
located and not in an anatomical position. However, the right ulnar, radial bones, and the
hand are all preserved and intact. The left shoulder as well as the left scapula and proximal
humerus are missing. The distal part of the humeral bone and the forearm are preserved with
the elbow joint intact. Part of the distal radial bone is missing. The left hand is preserved, but
the 5th metacarpal/phalanges are dislocated. No fractures are present.
Part of the left hip bone (the ilium) and part of the fractured coccygeal bone are preserved.
The ischium and pubis are missing. The right hip joint, including part of the acetabulum, is
partially preserved.
The right upper and lower limbs including the talus and calcaneus are preserved and
anatomically positioned. The knee is flexed at approximately a 30˚ angle. Tarsal, metatarsals,
and phalanges are also preserved, but separated from the ankle joint. The right femoral neck
shows multiple fractures.
Dental status. All teeth are present and only slightly worn (except the first molars, where
the dentin is largely exposed. The third molars show no dental wear at all. The only carious
lesion is found on the occlusal surface of 48 and the bone loss in only low. So, the dentition is
in good condition. The crown of the tooth 15 is fractured postmortem (Fig 9d).
Fig 9. SM5. a) sagittal MPR of the vertebral column, b) coronal MPR, c) axial slice showing degenerative changes with osteophyte formation (arrow)
and Schmorl’s node (arrowhead). d) 3D Volume rendering of the right side of the dentition (circle: Fractured 15) with sagittal 3D multiplanar
reconstruction (insert). Arrow: Carious lesion on occlusal surface of tooth 48.
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Histological findings. A sample from the right femur shows normal ‘necrotic’ cortical
bone without pathologic changes. No bacteria or fungi are identified (Fig 6; 121).
Salt Man #6 (SM6)
A fragmented skeletonized cranium and part of the pelvis have been found of SM6.
Radiological findings. The mandible and the part of the right parietal bone are missing;
the cranial cavity is filled with soil (Fig 8c & 8d). The skull shows multiple traumatic alterations
(which occurred peri-as well as porstmortem), including several fractures as well as ruptured
sutures, partially leading to impression of the cranial plates. The coronal suture as well as the
frontal portion of the sagittal suture are blown apart and the zygomatic process is disrupted at
the zygomatico-maxillaris suture on the right side. Additionally, the sphenosquamosa suture,
frontozygomatica suture, and sphenofrontalis suture are slightly disruptured on the right side.
The left parietal is fractured in the middle portion. The right orbit is fractured at the frontal
process of the maxillary bone. The right temporal bone, frontal bone, and the right orbit are
also fractured.
Dental status. The dental status of SM6 cannot be assessed radiologically, mainly due to
the poor resolution of the MPR. The following findings can be obtained from the available
photos: postmortem loss of 17, slight dental wear, and small cervical caries on the exposed
tooth necks of 16 or 21. Several rows of light linear enamel hypoplasias on the buccal surfaces
of the anterior teeth are visible.
Histological findings. Spongiosa and cortical bone can be visualized on a sample from
the parietal bone. No fungi or bacteria are identified (Fig 6; 123).
Age and sex determination
All Saltmen are assumed to be male, however not all the remains could be sexed thus far. Exter-
nal features such as facial hair are present in several mummies (e.g. SM1 and SM2), which con-
firms such individuals as male. The sex of SM3 has been estimated as presumable male by
some of the skeletal remains [10]. SM4 is estimated as being male. Molecular sexing using
ancient DNA (aDNA) was used for sex determination of SM5, confirming a male sex. The bio-
logical sex of SM6 is not fully identified. Only the imprecise data from the skull shape esti-
mated this idividual as a possible male. In this case, aDNA would clarify the sex, however these
analyses are still ongoing.
Age determination in adult skeletal material remains rather difficult [16]. In subadult indi-
viduals, it is usually performed by estimating bone age of the hand, according to the hand atlas
of Greulich and Pyle [17]. Additionally, bone atlases of the knee and feet can also be used
[18,19]. In forensic medicine, age estimation includes physical examination, assessing dental
eruption patterns, and bone age determination [20]. In adults, the sterno-clavicular joint and
the ossification status of the medial part of the clavicula is frequently used for age assessment
[15,21]. Other methods to determine age utilizing criteria such as prevalence of caries, dental
wear, or alveolar bone loss are problematic, at least from the age of 14 onwards, when dentition
is fully developed [22], and when only a few individuals of a population are assessed [23]. Food
preparation and consumption are often not fully understood in ancient populations, but have
a crucial influence on the development of oral diseases [24]. Therefore, when relaying upon
dentition, only a rough estimation of the age at death is possible.
With only the head preserved, age determination for SM1 is approximate, at best. The miss-
ing teeth, probably due to periodontitis, and the heavy dental wear estimate this individual was
likely an older adult. SM4 is of juvenile age, estimated to be 15–16 years old [9]. The radiologi-
cal analyses of SM5 indicate an age range of 45–49 years old. This estimation of an older age is
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Findings in ancient Iranian salt mummies
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corroborated by the degenerative changes in vertebral column. However, the dental findings
do not support such an older age range, since only slight dental wear is present, and the paros-
tatus is unremarkable. The age of SM6 cannot be further specified since the bones and teeth
are too fragmented.
Dentition and nutrition
The Saltmen show few caries, likely due to a low cariogenic diet. According to the archaeobota-
nic investigations, this is particularly surprising for the Sassanian mining period for which
there is ample evidence of horticultural activities and the presence of fresh fruits. Additionally,
the miners’ diet can be reconstructed via contextual findings of animal bones and macrobota-
nical remains as well as of paleofaeces that provide the best insight into food consumption [N.
Boenke in [4], 55–74]. According to the macrobotanical remains discovered at the excavation,
which were processed by wet sieving, there were remarkable differences between the Achae-
menid and Sassanian periods. While the grain and fruit supply was rather limited in the
Achaemenid period (including different variants of barley, some apricots and peaches), the
findings dating to the Sassanian is more variable (i.e. barley, wheat, durum and bread wheat
were consumed in addition to a high variability of nuts, olives and fruits, such as e.g. grapes,
figs, watermelons and plums). Varying degrees of dental wear are present in these mummies.
While the Sassanian Salt Men #1 and #2 show heavy dental wear, the Achaemenid Salt Men
#4, #5, and also the Sassanian SM6 show only mild wear. For SM4, the low degree of dental
wear is consistent with a younger age, while it is not explainable for SM5 or SM6. For the
older-aged individuals, especially of SM5, more dental wear would be expected. Although the
number of individuals is too low for a meaningful comparison, we may suspect a different way
of provisioning and preparing food. While the Achaemenid miners may have taken their pro-
visions to the mine and possibly cooked a stew of meat and barley (similar to other traditional
stews previously mentioned by Herodotus), this may have been different in the Sassanian
period, when horticultures were in the surrounding regions and supplied the miners with
fruits and vegetables. The grain was likely ground or even came to the site ground beforehand
which would have added abrasive minerals such as quartz particles to the meal. The more fre-
quent consumption of fresh, often acidic fruits may have further aggravated the abrasion by
the added erosive component [25]. The reason why the Sassanian SM6 only shows slight dental
wear may be because he is of a possible foreign origin, which was hypothesized with molecular
analyses [C. Warinner, A. Bowman in [4], p- 96].
Conclusion
In conclusion, the ancient Iranian Saltmen are the earliest known and only preserved cases of
natural salt mummies. They are a very rare example of historic salt miners, who most likely
died in accidental mine collapses. The individuals show a very heterogeneous state of preserva-
tion, which mainly results from the varying surrounding conditions in the salt mine. Multiple
traumatic lesions have been observed, but no intra-vitam pathologies.
Study limitations
We admit some study limitations such as incomplete skeletal material and technical limita-
tions (e.g. the CT-scan of SM6 is not sufficient for the analysis of dentition). For histological
analyses, only a few small samples were prepared for analysis in order to preserve the integrity
of the Saltmen. More invasive procedures would be needed to assess tissue or organ patholo-
gies, which is not appropriate with such valuable human remains.
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Findings in ancient Iranian salt mummies
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Acknowledgments
We thank the hospitals in Tehran (Pardis Noor and Tehran Heart Center) for conducting the
CT-scans (especially Dr. Sharam Aghlaghpour, Dr. Gholamreza Mowlavi and Dr. Shapour
Shirani). Furthermore, we thank the National Museum in Tehran (especially Dr. Fereidoun
Biglari and Dr. Jebrael Nokandeh) as well as the Archaeological Museum of Zanjān for the
support. We thank the Miras Farhangi, Zanja
ˆn for its logistical and personnel support. We
also thank Abagail Breidenstein, Institute of Evolutionary Medicine, University of Zurich, for
proofreading the manuscript.
Author Contributions
Conceptualization: Lena Maria O
¨hrstro¨m, Roger Seiler, Abolfazl Aali, Frank Jakobus Ru¨hli.
Data curation: Lena Maria O
¨hrstro¨m.
Formal analysis: Lena Maria O
¨hrstro¨m, Herman Marquez, Beata Bode.
Funding acquisition: Thomas Sto¨llner, Frank Jakobus Ru¨hli.
Investigation: Lena Maria O
¨hrstro¨m, Herman Marquez, Roger Seiler, Beata Bode, Thomas
Sto¨llner.
Methodology: Lena Maria O
¨hrstro¨m, Herman Marquez.
Project administration: Abolfazl Aali, Thomas Sto¨llner.
Resources: Beata Bode.
Supervision: Frank Jakobus Ru¨hli.
Writing – original draft: Lena Maria O
¨hrstro¨m, Herman Marquez, Roger Seiler.
Writing – review & editing: Lena Maria O
¨hrstro¨m, Roger Seiler, Beata Bode, Abolfazl Aali,
Thomas Sto¨llner, Frank Jakobus Ru¨hli.
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