Journal of Archaeology in the Low Countries 4-1 (October 2012)Raffaella Bianucci; Don Brothwell; Wijnand van der Sanden; Christina Papageorgopoulou; Paul Gostner; Patrizia Pernter; Eduard Egarter-Vigl; Frank Maixner; Marek Janko; Dario Piombino-Mascali; Grazia Mattutino; Frank Rühlis; Albert Zink: A possible case of dyschondrosteosis in a bog body from the Netherlands

3 Results

3.1 Histological analysis of bones and viscera

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3.1.1 Bone preservation

In spite of demineralisation and various damaged areas, histology performed on Zweeloo Woman’s bone fragments showed that important cellular structures such as Haversian canals and the lamellate structure have survived (fig. 3) (Pyatt et al. 1991).

There is no evidence of generalised destruction caused by mineral dissolution. Such alteration is characterised by the general loss of identifiable features such as bone lamellae, osteocytes and canaliculi (Hollund et al. 2011).

The high degree of preservation of the bone’s microstructure may indicate that the Zweeloo body was recovered from a slightly acidic peat bog with better bone tissue preserving qualities than highly acidic highland peat bogs (Petska et al. 2010). The acidic conditions of high-lying bogs often result in well-preserved bodies with excellent soft tissue preservation combined with totally decalcified bones (Bennike 2003, 39).

3.1.2 Viscera preservation

Our understanding of the long-term survival of viscera (i.e. lungs, heart, liver, blood vessels, kidneys and reproductive system) in bog bodies has increased in recent years.

The liver and kidney, the two organs in which the greater part of the volume consists of epithelial cells, are commonly reduced in size, deformed by the pressure of the peat bog layers or unrecognisable, whereas the lungs and intestinal wall (but not its lining epithelium) are usually the best preserved and most recognisable viscera (Aufderheide 2003, 175-176).

In our specific case we were able to confirm the results of the initial macroscopic identification. The paraffin sections of the kidney provided a perfect survey of the kidney tissue, including major characteristic regions such as the cortex and the renal pelvis (fig. 4A). Tubule-like structures were identified in the renal corpuscle (fig. 4B).

The liver material appeared to be less well preserved than the kidney sample. Nevertheless, liver parenchyma with polygonal-shaped hepatocytes and connective tissue could still be clearly distinguished in the paraffin sections (fig. 5A).

A relatively large number of eggs of the lancet liver fluke Dicrocoelium dendriticum was observed in the liver paraffin sections (B). Parasitological findings showing a case of true dicrocoeliasis in a bog body are reported elsewhere (Searcey et al. forthcoming).

3.2 Tissue preservation analysis by means of atomic force microscopy (AFM)

Of the various forms of connective tissue, collagen fibres are among the most important to survive in bog bodies. They preserve the shape of decalcified bones and the general structure of any remaining parts of the intestinal tract and define the body surface (Brothwell & Gill-Robinson 2002, 126).

AFM images revealed collagen fibrils with periodic banding patterns (figs 6, 7, 8) embedded in the tissue matrix. The average D-period, derived from topographic analysis along the longitudinal axis of several fibrils, was 62.8 nm (± 4.2 nm s.d.). The fibrils were unsorted, overlapping at some sites, and formed network-like structures.

Images taken at a greater level of magnification (figs 6, 7, 8) show uninterrupted collagen fibrils, although spherical particles may indicate collagen fragments. The fibril contour structure was very faint. Topographic analysis perpendicular to the longitudinal axis of several fibrils suggested a mean fibril height of 12.2 nm (± 3.6 nm s.d.).

Collagen is extremely durable and may survive in mummified tissue for several millennia (Chang et al. 2006; Janko et al. 2010). This indeed also holds for the structural preservation of the skin collagen of the Zweeloo mummy. As also observed in recent human skin and other mummy skin samples, the collagen fibrils in the skin of Zweeloo Woman were typically arranged in networks or sheet-like structures and showed a periodic banding pattern. Contrary to the results obtained by Stücker et al. (2001), who observed well-preserved collagen bundles in the dermis of six bog bodies, our results indicate moderate decomposition of the Zweeloo Woman collagen. The Zweeloo Woman collagen differs considerably in terms of fibril contour and size from the collagen found in recent human skin and other mummies.

High-resolution images taken with the AFM revealed soft outlines of the collagen fibrils, indicating an inferior degree of collagen preservation. The average characteristic banding pattern is 62.8 ± 4.2 nm, which is less than the value of 67 nm reported in the literature. The value is however still within the range of the error margin. The average fibril height of 12.2 nm (± 3.6 nm s.d.) is significantly shorter than that of recent skin collagen, which has a diameter ranging from 20 to 100 nm (Fleischmajer et al. 1981; Flint et al. 1984). This has also been observed in the case of other mummy skin collagen, such as that of the Iceman, whose fibrils were found to have a diameter of 32 nm (Janko et al. 2010).

The reduction in fibril height may be caused by decomposition, as observed in previous AFM studies (Paige et al. 2002; Bertassoni & Marshall 2009), which revealed the degradation of type I collagen by enzymatic action, e.g. by collagenase or papain-gel. In those studies it was suggested that the enzymes degrade the entire fibrillar structure in a non-specific manner, causing the fibrils to become both shorter and thinner.

An analogous effect may have occurred in the bog and have resulted in slight degradation, hence reduction in size, of the collagen. The differing degree of degradation is most probably due to variations in the composition, in particular the acidity, of the bog governing the preservation and mummification process.

3.3 Morphometrical analysis

3.3.1 Pathology: mesomelia

The skull shows clear evidence of a reduction in size (fig. 9) that also affected other parts of the body.

The frontal arc (85 mm) is probably 25 mm smaller than the smallest measurements of female skulls in northern Europe. The sagittal arc (93 mm) is similarly 20 mm smaller than usual for small skulls (Brothwell, personal observations).

These features are very unlikely to indicate microcephaly, a condition which does not normally reduce facial dimensions, but in this case the palate length (30 mm) is 15 mm less than usual.

If we consider ratios of humerus to radius length and femur to tibia, then an arm in a European would normally have a ratio around 1.4: 1.0. In this case it is 2.2: 1.0. The normal ratio of a leg is about 1.2: 1.0; that of Zweeloo Woman is 1.6: 1.0. So the level of reduction in both forearms is considerable, but the length ratio difference in the lower leg is far less, and also shows side-to-side asymmetry (the right leg ratio is 1.28: 1.0).

In the case of congenital reduction in longitudinal segments of the limbs in some forms of mesomelia, forearm reduction may result in ratios of 1.8: 1.0 (personal radiographic observations), which are similar to the Zweeloo ratio. We conclude that the congenital disorder of mesomelia is a possible explanation.

3.3.2 Stature

Estimation of dimensions on the basis of the outer body surface of the Zweeloo body led to an estimated stature of 155 cm (allowing for head and foot damage). Our measurement coincides with that previously provided by Stoddard (1995), who arrived at an overall stature of about 152 cm.

It should be noted that in a sample of 4.995 British women (Board of Trade 1957), 2.438 (49%) were between 141 and 159 cm, so these are not to be viewed as dwarfed statures. Therefore, Zweeloo Woman could be classified as an example of mesomelia. Approximate dimensions of other body measurements obtained for Zweeloo Woman are presented in figure 10.

The overall length of the trunk of Zweeloo Woman appears to be close to the British average for 30-44 year olds (Board of Trade 1957). The leg length, however, seems to be shorter (with due allowance for the damaged feet). The interacromion width of the Zweeloo body may be above average, but the waist circumference appears to be slightly smaller than the modern European mean. However, neither difference is significant.

Table 1 Measured lengths of bones (in cm) of Zweeloo Woman
	Length* in cm	Length in cm	Mean
	(RB, DPM)	(DB)
Right humerus	26.3	26.6	26.45
Left humerus	#	#	#
Right radius	12.1	12.5	12.3
Left radius	11.8	12.04	12.1
Right ulna	#	#	#
Left ulna	12.7	13	12.82
Right femur	32.6	(35.5)**	34.05
Left femur	#	#	#
Left tibia	21	21.8	21.4
Right fibula	21.6	#	#
Left fibula	18.1	#	#
# Fractured bones for which measurement could not be performed
* Lenghts defined in Brothwell (1981)
** Estimated with curvature corrected

The stature estimated on the basis of the bones of Zweeloo Woman ranges from 130 to 135 cm when the humerus, femur and tibia are included in the calculation, and from 137 cm to 141 cm when the tibia is excluded (Table 2).

Table 2 Stature of Zweeloo Woman estimated on the basis of the bones
Index*	Minimum	Maximum	Mean	Comparative data×
Humero/radial	46	47	46.5	76.6 ± 1.8
Femuro/humeral	80.1	74.4	77.7	71.2 ± 1.3
Femuro/tibial	65.2	62.1	62.9	81.6 ± 1.7
*Indexes after Martin (1928)
×Mean of 138 central European populations with a total of 14,730 individuals, after Siegmund (2010)

The Pearson method was considered the most appropriate among the estimation methods, since the employed reference series corresponds most closely to European populations in terms of body proportions (Siegmund 2010, 73-76) and Pearson considers all the long bones in the regression. In contrast, Trotter & Gleser (1952) consider only the tibia, and when the tibia is not available they use the femur. This calculation method would have led to distortions in the case of Zweeloo Woman due to the short length of the tibia and the curvature of the femur.

Comparison with a large dataset of an archaeological population from central Europe contemporary with Zweeloo Woman shows that she was significantly shorter than the mean (153.3 cm) of the female population of this period (Siegmund 2010, 83). With due allowance for the standard deviation and the interquartile range, 96% of the female population of this period ranged from 144.3 to 162.3 cm. Taking into account the bone shrinkage commonly found in bog bodies, the stature of Zweeloo Woman could be considered short, but within normal limits.

3.3.3 Body proportions

Besides the stature, the body proportions were also calculated according to Martin (1928, 1067) (Table 3) to enable us to evaluate the unusual proportions of Zweeloo Woman. The FHI and FTI are both significantly smaller than those of central European populations, which vary (Siegmund 2010, 62, 64). The HRI is extremely low due to the abnormal shortening of the radius.

Table 3 Body proportion estimation of Zweeloo Woman
Stature estimation with tibia	Stature in cm
Stature estimation method	Minimum	Maximum	Mean
Pearson (1899)	133.6	137.1	135.3
Trotter/Gleser, white (1952)	127.7	132.8	130.3
Trotter/Gleser, negro (1952)	127.3	131.9	129.6
Mean of Pearson, Trotter/Gleser	129.52	133.94	131.73
Stature estimation without tibia	Stature in cm
Stature estimation method	Minimum	Maximum	Mean
Pearson (1899)	139.4	143	141.3
Trotter/Gleser, white (1952)	134.6	141.8	138.2
Trotter/Gleser, negro (1952)	134.1	140.7	137.4
Mean of Pearson, Trotter/Gleser	136	141.8	138.9

3.3.4 Body Mass Index

The Body Mass Index (BMI) of Zweeloo Woman was calculated on the basis of the estimated stature and the femur head diameter using the formula of Auerbach & Ruff (2004) [which is actually a mean of the formulas of Ruff et al. (1991), McHenry (1992) and Grine et al. (1995) combined with Pearson’s method]. The BMI value of Zweeloo Woman is normal in comparison with present-day data provided by the World Health Organisation (2006), according to which values from 18.50 to 24.99 fall within the normal weight range ( Table 4).

Table 4 Body Mass Index estimation of Zweeloo Woman
		Stature estimation	Body Mass estimation (values in kilogram)
		after Pearson	after Ruff et al 1991	after McHenry 1992	after Grine et al 1995	mean (after Auerbach and Ruff 2004)	BMI
without tibia	min	139,4	40,46	33,99	38,34	37,60	19,34
	max	143,0	40,46	33,99	38,34	37,60	18,39
	mean	141,2	40,46	33,99	38,34	37,60	18,86
with tibia	min	133,6	40,46	33,99	38,34	37,60	21,07
	max	137,1	40,46	33,99	38,34	37,60	20,01
	mean	135,3	40,46	33,99	38,34	37,60	20,53

3.4 Radiographic analysis by means of CT scanning

3.4.1 Sex

The sex estimation was based on the pelvis and parts of the skull (White & Folkens 2005, 385-398). The following bones were entirely preserved: frontal bone, right and left parietals, a fragment of the left temporal bone and a fragment of the upper jaw. The reduced dimensions of the skull bones are due to post-mortem shrinkage and not microcephaly. True microcephaly does not result in such a pronounced reduction of the face.

The very small mastoid process of the skull and the shape of the pelvis (wider greater sciatic notches, longer pubic portion of the os coxae, larger subpubic angle, more elevated auricular surface) indicate that the individual was female.

3.4.2 Age at death

The age at death was tentatively inferred from various observations. Epiphyseal union in the long bones, pelvis and scapula indicates a minimum age of 25 years, while the morphology of the pubic symphysis points to an age between 35 and 50 years (Leopold & Schäfer 1998, 304-308; Byers 2005, 223-232).

3.4.3 Cut marks

There are at least 21 cut marks on the bones. Most of the cuts are short and were clearly made with a sharp blade. There is no evidence of bone reaction to these injuries, and there are no equivalent injuries on the body surface. The distribution of these injuries is shown in figure 11.

Briefly, the locations of these are as follows: (1) frontal, above the left orbit, (2) two on the inner aspect of the scapula blade, (3) a left hand phalanx and proximal phalanx of the left thumb, (4) the left femur below the trochanters and at the distal femur, (5) at the proximal articular end of the left tibia, (6) two at the distal end of the right humerus, (7) three on the right radius and one on the right ulna, (8) two on the right femur, in the upper and lower thirds of the shaft, (9) two at the proximal end of the right tibia and two more along the shaft. The cause of the damage is unclear, as there is no evidence of external body trauma, except possibly to the posterior aspect of the left shoulder, on the outer skin surface. It remains to be determined whether the cut marks were formed during the excavation or during the conservation of the remains.

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