Masaryk University Brno, Department of Anthropology, Faculty of Science Kotlářská 2, Brno, Czech Republic

Transcription

1 Variability and Evolution, 2003, Vol. 11: 5 30 ANALYSIS MIROSLAV KRÁLÍK, VLADIMÍR NOVOTNÝ Masaryk University Brno, Department of Anthropology, Faculty of Science Kotlářská 2, Brno, Czech Republic EPIDERMAL RIDGE BREADTH: AN INDICATOR OF AGE AND SEX IN PALEODERMATOGLYPHICS KRÁLÍK M., NOVOTNÝ V Epidermal ridge breadth: an indicator of age and sex in paleodermatoglyphics. Variability and Evolution, Vol. 11: 5 30, Tabs. 5, Figs. 9. Adam Mickiewicz University, Faculty of Biology, Institute of Anthropology, Poznań. Abstract: Epidermal ridge breadth of human fingerprints was investigated on ceramic artifacts from contemporary ceramic workshops. Our investigation has shown that mean epidermal ridge breadth (MRB) as observed on ceramics can be used as an indicator of age (from birth to maturity) and sex of the artifact maker in adulthood. In this study, we suggest a new method of scanning, measuring and data processing. The best age estimation method (using equation proposed by Kamp et al. from Grinnell College, USA, and modified after shrinkage by 7.5%) yielded results with mean error of estimates 0.18 years (SD = 2.36 years), median absolute error of estimates was 1.71 years and only in 3.6% of cases the absolute errors were higher than 5 years. Therefore, in a particular ethnic group epidermal ridge breadth of fingerprints on ceramics is suitable for comparing of individuals ages. The number of fingerprints and ridges per individual had no influence on estimation errors. In adults, sexual dimorphism was clearly present even though artifacts were made from different types of ceramic clays. Ridge breadth is 9% greater in males than in females. On the whole, MRB under 0.39 mm signifies a sub-adult individual under 15 years of age and MRB values over 0.52 mm come solely from adult males. However, age changes of ridge breadth in teenagers overlap with adult sexual dimorphism and therefore, in case of MRB values between 0.39 and 0.52 mm, variability in both age and sex should be taken into account. If this method is further developed, especially the qualitative aspects of fingerprints and properties of ceramic clay, it has great potential for illuminating the social background of ceramics-making in ancient cultures. Key words: fingerprints, ceramics, epidermal ridge breadth, age estimation, sexual dimorphism, paleodermatoglyphics

2 6 M. Králík, V. Novotný Introduction: Paleodermatoglyphics Archeologists frequently find artifacts imprinted with human fingerprints. Ancient fingerprints have been found on ceramics (e.g. Šikulová 1956; Pavelčík 1958; Klíma 1963; Šefčáková 1998; Einwögerer 2000), parchment (Bartsocas 1982), organic substance (Mania, Toepfer 1973; Koller et al. 2001) and other types of materials. Despite the diversity of archeological materials, it is ceramic clay, which has the optimal properties to be a transfer medium for fingerprints. Clay is sufficiently plastic for imprinting, and finger molding is a direct part of many manufacturing procedures. Fingerprints are mostly unintentional results of shaping, molding and touching wet clay. Once dried and fired, the clay hardens and becomes chemically stable which allows the prints to be preserved indefinitely; fingerprints on ceramics can even be preserved in shipwrecks buried in seawater (Corey 2002). At the same time, ceramic material is fragile, so the objects often break and need to be renewed. From the Neolithic to recent times, ceramics, especially various pots, form a significant part of the archeological record. Epidermal ridges and their arrangement (dermatoglyphic patterns) exhibit a number of properties that reflect the biology of an individual. Dermatoglyphic features statistically differ between the sexes, ethnic groups and age categories. Dermatoglyphs and their components are both environmentally and genetically determined, although the arrangement of ridges remains constant throughout life. Theoretically, it is possible to use human fingerprints on archeological finds similarly to skeletal remains: for estimation of interconnected biological properties of the people who left the prints. However, opposed to the obvious dermatoglyphic cards (ink-method), fingerprints on ceramics are fragmentary; they reflect heterogeneous regions of hand (friction skin, papillary terrain) and are likely to reflect more than one individual on one artifact. Studying such prints is more limited by the fragmentation and incompleteness of natural biological units (hand, thenar, finger-ball), than skeletal remains in skeletal anthropology. In reality, it is not possible to recognize particular area of the hand from the small print of epidermal ridges, so the methods of the standard dermatoglyphics are often inapplicable. Although dermatoglyphics has been experiencing a boom for decades (bibliographies e.g. Mavalwala 1977; Figueiras 1993) and dactyloscopy (police fingerprinting) is still the most widely used method of police identification of individuals, the study of fingerprints on archeological artifacts has not developed into a coherent approach with goals and methods. Ancient prints still continue to be dismissed as trivial curiosities even though the modern analysis of fingerprints first began after the discovery of fingerprints on Japanese prehistoric ceramics at the end of nineteenth century (Faulds 1880). Despite this situation, several innovative works have appeared during the second half of the twentieth century, frequently mutually unknown to the authors. Cummins (1941) divided prints on ceramics into intentional prints, which signify a meaning or

3 Epidermal ridge breadth: an indicator of age and sex in paleodermatoglyphics 7 signature, and unintentional prints, which are accidental results of molding. Others tried to identify fingerprints precisely and proceeded in dermatoglyphic analysis as far as possible. Their approaches focused on minutiae and the remaining dermatoglyphic patterns, while aiming to compare the character of ancient fingerprints with fingerprints of recent populations (Valšík 1951; Vlček 1951, 1952; Cseplák 1982; Szilvássy 1983). Sládek (1994) also reconstructed the shaping sequence of small figurines based on the position of fingerprints on their bodies. Åström and Eriksson (1980) used frequencies of dermatoglyphic patterns on ancient ceramics as an indicator of the ceramists ethnicity. Finally, some works focused on epidermal ridge breadth and its biological connections with sex and age (Basilidade, Rişcuţia 1974; Lička, Musil 1975; Primas 1975; Cseplák 1982; Kamp et al. 1999; Králík 2000; Králík, Novotný, Oliva 2002). During the International Conference on Dermatoglyphics, Athens, Greece, September 20 30, 1981, Bartsocas suggested the term paleodermatoglyphics to be used for the study of dermatoglyphics through antiquity in archeological and anthropological material (mummies), as well as in the ancient texts (Bartsocas 1982). For the Czech version of the paleodermatoglyphic history see Králík and Novotný (2003a, b). The English version is being prepared for printing. In contrast to other materials, the originator of a fingerprint on a ceramic item was necessarily in direct contact with the artifact at the time of its origin; he/she directly participated in its creation. A fingerprint on a potsherd is an example of direct association between culture and biology of an imprinted person. That is why we have been focusing mainly on fingerprints on ceramics. We have studied dermatoglyphic features that could be preserved in obvious fragmentary fingerprints on ceramics. Among them, ridge breadth has been chosen as a convenient variable observable on the majority of fingerprints. The present paper should be taken as a contribution to improvement of paleodermatoglyphic methods based on epidermal ridge breadth. Epidermal ridge breadth: definition and determination After Memorandum on Dermatoglyphic Nomenclature (Penrose 1968, p. 1): the true breadth of a ridge is defined as the distance between the center of one epidermal furrow and the center of the next furrow along a line at right angles to the direction of the furrows. The definition refers to classical black-ink fingerprints on white paper. Black lines of a fingerprint are called epidermal ridges like the original structures of the skin. With Penrose and others, we have to distinguish ridge breadth and printed ridge (line) width since the black line is a mere negative of the ridge top (Fig. 1). Unfortunately some authors used both terms breadth and width in the sense of Penrose s breadth. Since it is not possible to measure true ridge breadth from ink fingerprints (Penrose 1968), indirect methods (first used by Schlaginhaufen 1905) are used for determination of ridge breadth: the number of ridges crossing a defined line transversely is counted and the ridge breadth is a result of dividing the two figures. The line can be

4 8 M. Králík, V. Novotný Fig. 1. Epidermal ridge breadth of the epidermis (upper row), in ink fingerprint (middle row) and in plastic fingerprint on ceramics (bottom row). The left images are cross-sections and the right images are looking from above of a defined length and is placed upright on the stream of ridges, or in a defined position located between standard dermatoglyphic landmarks. Some authors used the line of a defined length and placed it transversely to the ridges on all dermatoglyphic regions (Cummins et al. 1941; Ohler, Cummins 1942), or in a single region. A bulk of works on dermatoglyphics determined ridge breadth as an additional variable to the well established a b ridge count (in the second interdigital area of the hand) (after Penrose, Loesch 1967). Only the measure of distance between a and b triradius had to be completed. Ridge breadth is obtained by calculating (DL+DR)/(CL+CR+2), where D is distance and C is the ridge count. Two ridges are added because triradial points are omitted in the ridge count. But the line joining a and b triradius may not be perpendicular to dermal ridges, especially when it is close to the triradius. Therefore the technique (a b ridge breadth) does not fully conform to Penrose s definition; in a sense it measures the ridge density but not the ridge breadth in a defined region. Another technique makes use of an equilateral triangle, whose apex lies in the center of a dermatoglyphic pattern and the two sides of 10-mm lengths are perpendicular to the stream of ridges of a distal parallel system (Loesch, Martin 1984a, b). Finally, Acree (1999) counted all ridges in a defined area of 25 mm 2 and Moore (1989) measured ridge to ridge distance from the center of one ridge to the center of the neighboring ridge.

5 Epidermal ridge breadth: an indicator of age and sex in paleodermatoglyphics 9 Some authors expressed their results in mean ridge breadth (in mm or μm) and others (predominantly in archeology and police fingerprinting) express their results in density of ridges (for instance 21 ridges per 1 cm). Epidermal ridge breadth: variability Since various authors employed different methods of measurement, the results are not completely comparable between the different studies. However, it is apparent from the results that many tendencies appear universally even when using the different methods, e.g. sexual dimorphism (Tab. 1). The first author who presented extensive reports on adult human epidermal ridge breadth on whole palm and fingers was Cummins and his co-workers (Cummins et al. 1941; Ohler, Cummins 1942). From their results it is evident that the epidermal ridge breadth varies considerably between different dermatoglyphic regions and also between the sexes. Ridges on the palm were coarser than on the fingertips. Digit I had a higher ridge breadth than all the other digits, the order of the decreasing ridge breadth was: I > II > III > V > IV and in the palm: thenar first inter-digital region > hypothenar > inter-digital II > inter-digital IV > inter-digital III. The ridges on the right hand are coarser. Hecht was the first author who reported on ridge breadth growth (Hecht 1924, cit. by Cummins et al. 1941). The average ridge breadth of single ridges in fingertip patterns was as follows: 0.15 mm (three premature infants); 0.18 mm (7 newborn infants); mm (10-year olds); mm (adult women); 0.50 mm (adult men); the numbers of participating subjects were not given in the latter three categories. Loesch and co-workers made the first equation of epidermal ridge breadth growth in the second interdigital area (a b ridge breadth) on a sample of Polish children from 0 to 12 years of age (Loesch, Godlewska 1971; Loesch, Czyżewska 1972). David (1981) studied a b ridge breadth and stated that at the age of more than 16 years the increase in ridge breadth was small. The difference between years olds and adults over 20 years old was not significant in either sex. In general, males have coarser ridges than females and the difference is approximately 10%. Ohler and Cummins (1942) were the first authors who exhaustively investigated sexual dimorphism in the epidermal ridge breadth. Sexual differences in a b ridge breadth are significant from the category of years of age (Loesch, Czyżewska 1972). The a b ridge breadth increases with the number of sex chromosomes (Penrose, Loesch 1967). The Y-chromosome affects the ridge breadth more than the X-chromosome. The a b ridge breadth in people with testicular feminization syndrome lies between the sexes although it tends to be closer to the values for females (compared to the males) (Polani, Polani 1979). Jantz, Parham (1978) studied the ethnic differences in the a b ridge breadth among Yoruba students (Nigeria), English (data from Penrose, Loesch 1967) and Jews (data

6 10 M. Králík, V. Novotný Table 1 Variability of epidermal ridge breadth with emphasis on sexual dimorphism. All results are converted to micrometers. Differences between the sexes in each sample are presented also as percentages with reference to males Authors Comment Sample n Mean (SD) [µm] Diff. [%] Males Females Hecht 1924 Fingers 500 Hecht 1924 Fingers Cummins et al All regions combined 4/5 Euro Americans, 1/5 Jews (29) Ohler, Cummins 1942 All regions combined 90% Euro Americans, 10% Jews (27) Cummins et al Ball of II-nd finger 4/5 Euro Americans, 1/5 Jews (42) Ohler, Cummins 1942 Ball of II-nd finger 90% Euro Americans, 10% Jews (34) Loesch, Martin 1984b Triangle, finger IV Australians of European origin (38) Loesch, Martin 1984b Triangle, finger IV Polish, adults (37) 9 2 Loesch, Martin 1984b Triangle, finger IV Polish, adults (38) Loesch, Martin 1984b Triangle, finger III Australians of European origin (47) Loesch, Martin 1984b Triangle, finger III Polish, adults (43) 32 7 Loesch, Martin 1984b Triangle, finger III Polish, adults (36) Cummins et al II-nd interdigital area 4/5 Euro Americans, 1/5 Jews (50) Ohler, Cummins 1942 II-nd interdigital area 90% Euro Americans, 10% Jews (39) Penrose, Loesch 1967 A b ridge breadth English, over 20 years (41) 51 9 Penrose, Loesch 1967 A b ridge breadth English, over 20 years (39) Losch, Czyżewska 1972 A b ridge breadth Polish, from 12 to 13 years (41) 21 4 Losch, Czyżewska 1972 A b ridge breadth Polish, from 12 to 13 years (30) Losch, Czyżewska 1972 A b ridge breadth Polish, from 13 to 14 years (56) Losch, Czyżewska 1972 A b ridge breadth Polish, from 13 to 14 years (50) Katznelson, Ashbel 1973 A b ridge breadth Jews (45) 51 9 Katznelson, Ashbel 1973 A b ridge breadth Jews (74) Jantz, Parham 1978 A b ridge breadth Yoruba (55) 49 8 Jantz, Parham 1978 A b ridge breadth Yoruba (41) Polani, Polani 1979 A b ridge breadth (43) 38 7 Polani, Polani 1979 A b ridge breadth (44) David 1981 A b ridge breadth 20 years and more (48) 49 9 David 1981 A b ridge breadth 20 years and more (43) David 1981 A b ridge breadth From 16 to 19 years (49) 47 9 David 1981 A b ridge breadth From 16 to 19 years (38) Stücker et al Original method, fingers Dactyloscopic database (89) 44 9 Stücker et al Original method, fingers Dactyloscopic database (49) Moore 1989 Original method, fingers Dactyloscopic database Moore 1989 Original method, fingers Dactyloscopic database Primas 1975 Fingerprints on ceramics (41) Primas 1975 Fingerprints on ceramics (34) present data Fingerprints on ceramics Czech, adults (36) 44 9 present data Fingerprints on ceramics Czech, adults (31) from Katznelson, Ashbel 1973). Ethnic differences were substantial in both sexes. Loesch and Martin (1984b) also discovered that the ridge breadth on fingers III and IV in Polish and Australian males of European origin were different, i.e µm and µm (for finger III), µm and µm (for finger IV), respectively. The ridge breadth covaries with other dermatoglyphic features. In fingers the ridges are coarser in the ulnar loops than in whorls (Cummins et al. 1941). There is

7 Epidermal ridge breadth: an indicator of age and sex in paleodermatoglyphics 11 a negative correlation between the breadth of ridges and the number of minutiae of the end type on fingers IV and III indicating that narrow ridges are more likely to be interrupted by ends (Loesch, Martin 1984b). However, a b ridge breadth and ridge count of the first finger are entirely independent traits (Loesch, Lafranchi 1990). The epidermal ridges, between which interstitial ridges are present, are significantly further apart from each other than those without interstitial ridges (Stücker et al. 2001). The epidermal ridge breadth also correlates with some anthropometrical parameters. Ridge breadth correlates with hand length, hand breadth and breadth of the distal phalanx (Cummins et al. 1941). However, the authors discovered that the coefficient of variation of the epidermal ridge breadth was much higher than the coefficient of variation of hand length. Therefore, ridge breadth is subject to a wider variation than hand size so there must be another factor than size of hand, that influences ridge breadth. Loesch and Lafranchi (1990) showed that the a b ridge breadth is closely related to wrist width. In adults the coefficient of correlation between ridge density and body height was 0.16 (Cummins et al. 1941) and because it is consistent in all dermatoglyphic regions when considered separately, the authors regard the relation as true. The a b ridge breadth correlates positively with chest circumference but only slightly positively with the body mass index (BMI) and negatively with the length of the lower limbs % of the variability in body measurements is accounted for by the variability in breadth of individual s ridges (Loesch, Lafranchi 1990). On the whole, the variability of the epidermal ridge breadth in humans is substantial. The greatest changes in the ridge breadth occur between birth and maturity. Sexual dimorphism in epidermal ridge breadth was also verified by many samples. Nevertheless it must be noted that differences between single ridges in a limited area of the epidermis may be higher than the variability between individuals and groups described by mean values, regardless of the mean breadth determination method. Ridge breadth values from prints on ceramics are closest to the values for finger balls of distal phalanges, and this is the case for both the mean values and the variability patterns (Tab. 1). Ridge breadth of fingerprints on ceramics The appearance of an epidermal ridge imprinted on ceramics is caused by the contrast between light and shadows on a three-dimensional negative. The distance between the edges of one shadow and the same point on the edge of the next shadow vertical to the edges, corresponds to ridge breadth (as defined by Penrose). Therefore the ridge breadth can be measured directly (Fig. 1). Clay, however, is not completely homogenous the dimensions of the mineral grains are often comparable to the ridge dimensions. So, the mineral grains can distort details of the ridges and its borders. Therefore it is better to measure a bundle of ridges. On the other hand, a fingerprint on

8 12 M. Králík, V. Novotný a ceramic piece is three-dimensional, frequently more or less concave. Hence the linear measure is more a tangent of the curve, rather than the true length of the curve. Moreover, recording haphazard fingerprints on ceramics is not standardized. Since the epidermal ridge breadth varies considerably between various dermatoglyphic regions of one individual, and even between sections of a particular dermatoglyphic region, an uncontrolled set of tiny fingerprints is a rather questionable representation. Besides, the epidermis is elastic so during imprinting it is temporarily deformed due to the forces and their directions. The prints reflect the deformation event. This is caused by factors such as softness of the epidermis and clay hardness. Fingerprints just formed on the wet clay can be deformed by subsequent molding. Substantial changes of the ridge breadth might occur as a result of the deformation. The ridge breadth can increase or decrease especially in artifacts made by free hand or when there is excessive amount of water in the clay. Therefore it is important to exclude at least visibly deformed fingerprints from metrics. Unfortunately, it is not so easy to distinguish deformed and non-deformed fingerprints. Finally, the clay body changes during drying and burning the absolute size of the artifact as well as the impressions on its surface change. Linear shrinkage of ceramics varies between 0 and 20% (on average 7 10%) (Lach 1989), which is similar to, for example, sexual dimorphism (see Tab. 1). However, at the present time a precise estimation of the shrinkage of the finished ceramic matter is not possible. To sum up, the biological variability of the ridge breadth as imprinted on ceramics is confounded by many factors: shrinkage, pressure deformation, unknown application of fingers and palms in molding. It is not certain if any reasonable metric estimation is possible and if unknown factors do not destroy the useful biological trends. Ridge breadth in retrospective estimations In spite of these well-founded doubts, several works used epidermal ridge breadth in paleodermatoglyphics. Primas (1975) evaluated fingerprints on pottery from Heuneburg (Germany) and she attempted to estimate sex of the creators based on the epidermal ridge breadth. The material was from Iron Age, when, in many parts of Europe, we can detect a transition from handmade domestic pottery, to pottery as a specialized craft where the items were manufactured on the pottery wheel. In one collection of fingerprints on pots with a stepped edge, Primas discovered that these fingerprints had an average of 19.1 ridges per 1 cm. Based on reference values (according to the works of Cummins et al and Ohler, Cummins 1942), and her own experimental measurements of recent populations (females: 23.2 ridges per 1 cm, males: 20.8 ridges per 1 cm), she attributed these prints to males. She concluded that the Golasecca culture (9 th century B.C. to the 4 th century B.C.) can be noted for the manufacture of advanced pottery by male craftsmen with all the social consequences and influences it had on the neighboring cultures.

9 Epidermal ridge breadth: an indicator of age and sex in paleodermatoglyphics 13 We can also mention the work of Basilidade and Rişcuţia (1974) who studied ridge breadth of fingerprints on Romanian Neolithic ceramics. They attributed these prints to males based on the mean ridge breadth of 0.55 mm. Lička and Musil (1975) provided interesting information about the application of fingerprints, especially the ridge breadth in archeology and criminalistics. Acree (1999) introduced a method of sex assessment from fingerprints to criminalistics, also based on epidermal ridge breadth. Cseplák (1982) published a report on finger and nail prints on fragments of Neolithic pots years old from Hungary. The epidermal ridge breadth varied between 270 and 600 μm. Kamp et al. (1999) published seminal research of exemplary quality that represents a new direction for future research in paleodermatoglyphics. This work involves a critical theoretical approach based on extensive dermatoglyphic literature, suggested method, experimental testing of methodology and the development of a model, application of the model to specific data and the interpretation of results, taking into account all the relevant information. The authors obtained fingerprints by experiment and measured the ridge breadth directly on the ceramics with digital calipers. They developed a linear regression model of the growth of the epidermal ridge breadth during postnatal growth and maturation (from 5.4 to approx. 21 years of age). The model was then applied to two artifact assemblages of Amerindian utilitarian and funerary ceramics from northern Arizona. On the basis of the discovered differences the authors demonstrated that one pottery type the zoomorphic figurines were manufactured by children, and the second type craftsman-quality pots were manufactured by adults. They also developed a model for the relationship between ridge breadth and body height during postnatal growth. This is the best work in paleodermatoglyphics so far and it represents great progress in this field. In his Master s thesis, Králík (2000) reviewed the current state of paleodermatoglyphics and experimentally attempted to find the best method for estimating age from birth to adulthood based on the epidermal ridge breadth. The ridge breadth was computer-measured from photographs. On a small sample of 140 prints on ceramic artifacts from 13 individuals, the author tried to deal with the main unknown factors affecting ridge breadth data and estimation. In 6 steps he generated several theoretical variants of shrinkage, selection of fingerprints, measurement method, mean value counting and regression equations. By combination of all variants, 432 different protocols for age estimations were obtained. Differences between the age estimates and the true ages from each protocol were subjected to statistical analysis. The equation that originated from fingerprints on ceramics (Kamp et al. 1999) provided the best estimations. The best estimations were achieved when the ridge breadth was multiplied by a coefficient of (according to common shrinkage of ceramic clay 7.5%). The mean absolute difference between true age and estimates was 2.03 years and only in 3.3% estimations it was more than 5 years (Abstract Králík 2003). Králík, Novotný and Oliva (2002) rediscovered a forgotten fingerprint on the Venus figurine from Dolní Věstonice (Gravettian, 25,000 B.P.) found in Moravia,

10 14 M. Králík, V. Novotný Czechoslovakia, in According to the ridge breadth (0.37 mm), the fingerprint maker may have been a sub-adult individual or an adult female but probably not an adult male. However, this one and only fingerprint available is very small in size and therefore within the limit of observability. It might represent a point at the extreme end of the range of variability. It is also possible that the wet clay was deformed with the fingerprint. Moreover, the maker of the fingerprint may not be the creator of the artifact. Research is currently continuing on fingerprints on Central European Gravettian ceramics from sites at Dolní Věstonice, Pavlov (Czech Republic) and Krems (Austria). The results are expected to contribute to clarifying the origin and function of these ceramics, the oldest ceramics in the world. In this article we would like to test several equations for the estimations of age from the ridge breadth on a larger sample of ceramics than was used by Králík (2000), and attempt to evaluate the effect of age changes and sexual dimorphism on ridge breadth. The natural character of fingerprints, unaffected by our presence, and the large variability of ceramic factors, are emphasized at the expense of totally controlled conditions and the statistical design of the sample. Material The material consists of recent artifacts (Fig. 2) made by three different groups (setting) of individuals of known age and sex. One group represents works of 56 children from the Tišnov Primary School of Art (Moravia, Czech Republic). All artifacts were created before our first contact with the school. The authors applied several techniques during the creation process: shaping by free hand, lathing on potter s wheel, cutting out of kneaded plates, building from kneaded plates. Thus, with respect to hand and finger mechanics, the fingerprints were the results of various printing conditions. Artifacts were created from several types of clay. In the majority of artifacts, the type of clay and its shrinkage was ascertained. Since artifacts were made during normal teaching lessons with the children together in one classroom (workshop), an artifact made by a particular child may also bear the fingerprints of his/her classmates. The second group consists of works of 20 adult professional ceramists, 6 males and 14 females, from 20 to 61 years of age. The artifacts were obtained at retail outlets and were made (formed, dried and burnt) under real-life conditions of present day ceramics production/creation. Thus, the artifacts were manufactured before our first contact with the author or a particular ceramic studio so aspects of shrinkage could not be ascertained. Various clays were used. The fingerprints from this group were used to test sexual dimorphism. By our special request, non-professionals unskilled in ceramic making produced the third group of artifacts (small figurines and pots) from ceramic clay (provided by us), while we were present. Adults from this group (17 males and 13 females from 19 to 77 years of age) were added to the adult professionals to test sexual dimorphism. In

11 Epidermal ridge breadth: an indicator of age and sex in paleodermatoglyphics 15 Fig. 2. Examples of ceramic artifacts used for fingerprint analysis (children from Tišnov Primary School of Art row 1 and 2; professional ceramists row 3 and 4) this group, the sub-adults (15 persons) were added to illustrate the overall variability of ridge breadth in relation to age and sex. All artifacts were evaluated after ceramic shrinkage and burning. The fingerprints of the three groups were automatic and unintentional results of the molding. All authors were of Czech origin and lived in western Moravia, near the town Tišnov. Age of each subject at the time of molding was retrospectively ascertained in months and recounted to years (i.e years). In some adult professionals the age was rounded off to whole years. Artifacts surfaces were complex. Fingerprints were fragmentary; frequently no dermatoglyphic pattern was distinguishable. Preservation of ridges substantially varied from one part of the fingerprint to another. Sometimes, two parts of one fingerprint

12 16 M. Králík, V. Novotný seemed to indicate two separate fingerprints. In other cases, several (two or more) fingerprints were superimposed on each other. (We called this situation cross fingerprints.) In order to deal with this complex situation it was essential to define the fingerprint as a unit of analysis. Our definition of a fingerprint is the part of ceramic surface with friction skin negative that was naturally separated from the others of its kind, or one that was artificially separated for the purpose of photography. In spite of the above-mentioned complexities, the majority of the single fingerprints represented one single imprinting event. The size of the fingerprints varied, from approximately several square millimeters to several square centimeters. Method Only well-preserved fingerprints were recorded. Blurred, deformed and unclear fingerprints were discarded. A total of 568 fingerprints were included in the study. For scanning the fingerprints (Fig. 3) we used macro-photography camera Nikon Coolpix 4500, 4 Mpix. Artifacts were fixed by dipping in coarse sand or mustard seeds in an appropriate container and photographed. Light was provided by a halogen lamp. Calibration of the images was provided with a square of calibrated paper (3 3 mm) placed near each fingerprint parallel to its surface plane. To minimize lens distortion near the margins of the field of vision, fingerprints and calibration were situated in the center of the image. The axis of the camera was perpendicular to the fingerprint surface. Photos were then processed on a personal computer via image analysis software UTHSCSA ImageTool for Windows Version We measured the width of a bundle of ridges on the longest possible section perpendicular to the stream of ridges and counted the number of involved ridges. The mean value of ridge breadth from each measurement was a result of dividing the Fig. 3. Schematic representation of the recording of fingerprints

13 Epidermal ridge breadth: an indicator of age and sex in paleodermatoglyphics 17 Fig. 4. Depiction of epidermal ridge breadth and its measurement on a ceramic piece two figures. The mean ridge breadth was calculated from several measurements on each fingerprint (Fig. 4). The mean value for each artifact the mean epidermal ridge breadth of an individual (MRB) was calculated from the values of all fingerprints on a particular artifact. In the case of more artifacts being made by one individual, the individual value was obtained from all fingerprints of the particular individual. During these measurements the author s identity was unknown. For estimations of the age from MRB we used the following equations (Fig. 5): LC equation after Loesch and Czyżewska (1972): y = x (y MRB in μm, x age in years). LCmod equation after Loesch and Czyżewska (1972) modified by recounting according to the mean ridge breadth ratio between hand and fingers in males (according data from Ohler, Cummins 1942) combined with shrinkage (7.5%), the ridge breadth in equation was multiplied by x = (y ) / (y MRB in μm, x age in years). KA equation after Kamp et al. (1999): y = 614 x 112 (y age in months, x MRB in mm). KAmod equation after Kamp et al. (1999) modified according to shrinkage rate of 7.5% (this estimation provided the best results on a pilot sample, Králík (2000)), the ridge breadth was multiplied by y = x 112 (y age in months, x MRB in mm). PM1 simple linear regression equation obtained directly from our present data; MRB was the independent variable. PM2 simple linear regression equation obtained directly from our present data; MRB was the dependent variable. One assumption of the least squares model is that the independent variable is measured without error. This is more likely to be the case for age than epidermal ridge breadth. The second reason for introducing PM2 was

14 18 M. Králík, V. Novotný Fig. 5. The relationship between age and mean epidermal ridge breadth including the linear regression models used for estimation comparison with equation LC, where the age was also the independent variable. KAts equation after Kamp et al. (1999) modified according to true shrinkage of each ceramic matter, which were empirically ascertained y = 614 ts x 112 (y age in months, x MRB in mm, ts true shrinkage). True shrinkage varied between 7% and 12%, so ts is different in each case. For each equation we calculated the differences between the true and estimated age errors of estimates, which were subjected to statistical analysis. Since sex assessment from fingerprints is not possible at present in the study of age differences, we include boys and girls in the same group. Absolute errors (positive values of errors) of PM1 were used to study the relation between the number of measured units (fingerprints, ridges) per individual, and the accuracy of estimation. In adults, we compared the differences in MRB between sexes and between professionals and non-professionals. Statistical operations were performed in the STATISTICA version 6, StatSoft, Inc. (2001) and Rundom Projects Version 1.1 (Jadwiszczak 2003). Results Age estimations In a sample of 56 individuals aged between 5.92 and years there was an underrepresentation in younger categories and also a disproportion in sexes (13 boys and 43 girls). Since this sample includes all children attending the ceramic workshop it was a natural sample of young ceramic makers and the disproportion of sexes is likely to reflect gender preferences for ceramic making.

15 Epidermal ridge breadth: an indicator of age and sex in paleodermatoglyphics 19 Although our data did not fulfill all the assumptions for the parametric least squares model (unequal number of subjects in individual age categories), we built linear regression equations (sexes combined): PM1: y = x (y age in years, x MRB in mm). (r = 0.681; r 2 = 0.464; F(1;54) = ; p = 0.0; Std. Err. of Estimate = 2.381) PM2: y = x (y MRB in mm, x age in years) (Std. Err. of Estimate = 0.031) Descriptive statistics of errors for all equations are given in Tab. 2 and Fig. 5. Given the nature of the models there is no difference in means between PM1 and PM2 (Tab. 3, Fig. 6). However, the variability of estimates is significantly greater in PM2. Although the difference between KA and PM1 is significant, variances of errors for KA and PM1 are identical because slopes of the models are almost identical (correlation coefficient between errors of KA and PM1 is ). Differences in mean errors of LC and PM1 are substantial but differences between variances of LC and PM1 errors are not significant. The mean for LCmod is close to zero and differs insignificantly from PM1 but its variability is higher than results from all other equations, except PM2. Errors from KAmod differ only by 0,18 years from zero and although this value is significantly different from PM1, variability around mean is indistinguishable from PM1. Results of KAts are insignificantly higher than PM1 and the variance of KAts significantly differs only from LCmod and PM2. Model PM1 yielded the best results. Since it was based directly on the data, we consider KAmod the best equation for the estimation of age. Mean absolute error of estimates of KAmod was 1.87 years (SD = 1.43), median absolute error was 1.71 years. In 60% of cases absolute error was lower than 2 years, in 91% of cases lower than 4 years, and only in 3.6% of cases the absolute error was higher than 5 years. Valid n = 56 Descriptive statistics of errors of estimates (in years). Negative errors are underestimations Mean Conf. 95% Conf. +95% Median Var. SD St. Error Perc. 5 Perc. 95 Min. Table 2 Max. LC LCmod KA KAmod PM PM KAts

16 20 M. Králík, V. Novotný Fig. 6. Errors of estimates from different equations Table 3 Comparison of means and variability of estimation errors obtained from applied equations (significant differences highlighted) n = 56 LC LCmod KA KAmod PM1 PM2 KAts S = S = S = S = S = S = LC p = 0 p = 0 p = 0 p = 0 p = 0 p = 0 LCmod L = 1.71 p = 0.19 KA L = 1.29 p = 0.26 KAmod L = 1.34 p = 0.25 PM1 PM2 KAts L = 1.31 p = 0.26 L = 2.67 p = 0.11 L = 0.93 p = 0.34 L = 5.57 p = 0.02 L = 5.64 p = 0.02 L = 5.59 p = 0.02 L = 0.13 p = 0.72 L = 4.76 p = 0.03 S = p = 0 L = p = 0.97 L = p = 0.99 L = 6.94 p = 0.01 L = 0.02 p = 0.88 S = p = 0.01 S = p = 0 L = 5.56 p = 0.98 L = 7.02 p = 0.01 L = 0.03 p = 0.85 S = p = 0.07 S = p = 0 S = 9.81 p = 0 L = 6.97 p = 0.01 L = 0.03 p = 0.87 S = p = 0 S = p = 0 S = 9.81 p = 0.59 S = 0 p = 1 L = 6.08 p = 0.01 S = 26.2 p = S = p = 0 S = p = 0 S = 4.85 p = 0.14 S = 4.85 p = 0.77 Upper matrix: Fisher s paired comparison randomization test (two-sided test), randomizations, S (sum of pair differences) and p. Lower matrix: Levene s test for constant variance, randomization version, randomizations, L (Levene s F) and p

17 Epidermal ridge breadth: an indicator of age and sex in paleodermatoglyphics 21 Mean error (PM1) for males is 1.11 years (SD = years), for females years (SD = 2.466). The method overestimated the age of males and underestimated the age of females. The difference is of marginal significance (t-test: p = 0.052; two-sample randomization test: p = 0.052), it may be due to the absence of boys in the oldest age category where sexual dimorphism is well expressed. The number of ridges of each individual varied from 27 to 287, the number of fingerprints from 2 to 8. Outliers (363 and 447 ridges on 11 and 16 fingerprints respectively) were excluded from this analysis. We divided the cases into two groups according to the success of the estimations (absolute errors) of PM1. In estimates with absolute error lower than 1.57 years, each individual has an average of 4.62 fingerprints and an average of ridges. In estimates with absolute error higher than 1.57 years, each individual has an average of 4.33 fingerprints and an average of ridges. There is some tendency for better estimates when more ridges and fingerprints were measured but it is not statistically significant for the number of ridges (t-test: p = 0.14; two-sample randomization test: p = 0.14) nor the number of fingerprints (t-test: p = 0.47; two-sample randomization test: p = 0.52). Sexual dimorphism Differences in mean ridge breadth (MRB) between sexes in adults (Fig. 7) were tested using two-sample randomization tests for mean differences. For both groups, the professionals (17 males and 13 females) and the non-professionals (23 males and Fig. 7. Differences in mean ridge breadth (MRB) between sexes

18 22 M. Králík, V. Novotný Table 4 Sexual dimorphism in MRB and differences between professionals and non-professionals Mean [mm] n SD Males professionals non-professionals Females professionals non-professionals All Comparison of means and variability of MRB in adults (significant differences highlighted) (1) (2) (3) (4) Males professionals (1) p = 0.29 p = 0.02 p = 0.31 non-professionals (2) p = 0.12 p = 0.00 p = 0.00 Females professionals (3) p = 0.07 p = 0.80 p = 0.08 non-professionals (4) p = 0.23 p = 0.74 p = 0.57 Table 5 Upper matrix: p of two-sample randomization test, randomizations. Lower matrix: p of Levene s test for constant variance, randomization version, randomizations 27 females) significant differences between the sexes were found (Tab. 4, 5). When the differences between the professionals and the non-professionals are considered separately for each sex, they were not significant, so the combined mean value for each sex was calculated as follows: males mm (SD = 0.036), females mm (SD = 0.031). The mean values were compared to the mean values (see Tab. 1) obtained by Primas (1975). The differences were not significant for males (two-sided t-test: p = 0.096; Fisher s one-sample two-sided randomization test: p = 0.1) and significant for females (two-sided t-test: p = 0.005; Fisher s one-sample two-sided randomization test: p = 0.006). Combining age and sex We can evaluate the overall variability of mean ridge breadth (MRB) (Fig. 8) according to sex and age, irrespective of the professional skills of authors and ceramic clays being used. Sub-adults and adults from previous comparisons were combined and 15 children (non-professionals) were added. (Imprints of two extremely young children were obtained by putting small pieces of clay into their hands as a toy.) All our subjects with MRB values below 0.39 mm were sub-adults under 15 years of age, all those with MRB values over 0.52 mm were adult males. MRB values between these two figures represent people of both sexes from an age of 8.83 years

19 Epidermal ridge breadth: an indicator of age and sex in paleodermatoglyphics 23 Fig. 8. The relationship between age and mean epidermal ridge breadth, all groups combined (a boy) to an old age. Therefore all estimations of age from MRB over 0.39 mm lie in the zone of overlap with adults. The difference between female subjects 15 to 20 years old (n = 12, mean = mm, SD = 0.023) and adults (n = 27, mean = mm, SD = 0.031) was significant ( permutations, two-sample randomization test: p = 0.039; two sample bootstrap t-test: p = 0.039). In males, the difference was not tested due to the small number of boys. Discussion and conclusion Our results are in agreement with most other studies, in that the measurement of the epidermal ridge breadth of fingerprints on ceramics might be used as an indicator of the ceramists age and sex. These biological trends are present not only on controlled laboratory samples in experimental conditions but also in retrospectively ascertained conditions of contemporary ceramic production. We have to note some disproportion in sexes among present ceramists in favor of females, both in children and in adults. The question is if this situation is specific only for our recent conditions or if it is a general trend in ceramic manufacturing.

20 24 M. Králík, V. Novotný Concerning the age estimation, using the regression model by Kamp et al. (1999) resulted in errors of the same variability as the model based directly on the present data (PM1). After correcting for shrinkage of clay (7.5%) Kamp s model (KAmod) yielded results with mean value of errors near zero even though our sample came from a different population and we used a different measurement technique. However, we have to comment on a very surprising correlation (r = ) between errors of the present model and the model by Kamp et al. (1999). Theoretically, if the sexes in our sample were in proportion, the regression line for our model (PM1) would shift slightly. The correlation coefficient would then be lower. Some differences between the two samples are also apparent from the results based on true shrinkage (KAts results). Let us assume an equal proportion of females and males in the study of Kamp at al. (1999). The shrinkage rate assumed in the KAts model is based on empirical values therefore it should be optimal. Thus, when the KAts model is applied to our sample (overrepresented by females), it is more likely to underestimate age than to overestimate it because of sexual dimorphism; lower values in females should lower the estimations. Despite these expectations, the KAts model slightly overestimated the age. This could indicate some systematic shift either due to differences between the techniques and/or differences between the populations. So the above-mentioned unusually high correlation coefficient is a result of an accidental interplay of several factors; nevertheless, the similarity of the two models (KAmod and PM1) is a good indicator of the applicability of this biological trend to age estimation. Since the actual shrinkage rates of prehistoric ceramic artifacts are unknown we consider the equation by Kamp et al. (1999), when corrected for shrinkage by 7.5% (Králík 2000), the best tool for estimates of age in paleodermatoglyphics today. In future, it would be very beneficial if methods allowing accurate detection of the shrinkage rate of a particular piece of ancient ceramics, could be developed. Equation by Loesch and Czyżewska (1972) severely underestimated the actual age. After modifying this equation (from palm to fingers and from paper to ceramics), the estimations substantially improved the mean error so the compensation was almost optimal. The slope of the regression line changed after correcting of the equation (i.e. multiplying the ridge breadth); this increased the variability of errors. At first sight it may seem that adding (rather than multiplying) a constant is a better modification. Since the size of imprints on ceramics changes proportionally (i.e. we cannot correct for it by adding a constant) the increase of variability after our correction may indicate actual differences between our sample and the Polish sample (this also applies to the differences between KA and KAmod). From the available data it is not possible to determine whether the low predictive power of LCmod is because it was originally not developed for this purpose (i.e. fingerprints on ceramics), or because it uses the MRB as the dependent variable. However, the similarity of the LCmod regression line with the line of our second model (PM2) may also indicate that using ridge breadth as dependent variable in regression is entirely inappropriate for age estimates.

21 Epidermal ridge breadth: an indicator of age and sex in paleodermatoglyphics 25 Changes in MRB connected with age during growing up consistently peter out around the age when sexual differences are established. Tendencies for higher values in boys are apparent from the age of ten. Based on the summary graph, women reach adult values before men. However, the low number of men in our age sample may cause this pattern. On average, ridge breadth is 9% thinner in women compared to men, however the overlap is marked. The threshold between children and maturity seems to be the value of 0.4 mm. Above this value, MRB on its own is not an adequate indicator of age. For example, a print with MRB value of 0.43 mm can belong to an immature individual or an adult, but is more likely to be a female than a male. The graph (Fig. 8) also shows that a 12 year-old female can have an MRB value above 0.46 mm, even though we only know of one such case. Although it is not out of question that some of these borderline cases can indicate the presence of more than one subject, in our opinion, age estimates from MRB values higher than 0.4 mm will always be uncertain, because age and sexual dimorphism can be acting together. This is not only the case in estimates in individual artifacts but also in a more general sense when comparing groups of prints or artifacts. It would be helpful if the sex of the author of the prints could be determined. Although the difference between professional ceramists and non-professionals was not statistically significant, it is consistent in both men and women. This could indicate that this is a real trend, regardless of whether it is caused by differences in clay molding or actual biological differences. The oldest female subject in our sample, who spent her life laboring on the land, had coarser ridges than the majority of the male subjects. So the question is, to what extent can high loading on the hands over a long-term period change the epidermal ridges. Can it be postulated that hard labor was more common in past agricultural societies than today? Our procedure assumes a simple relationship: 1 artifact = 1 individual, in other words, in a particular artifact we expect to find prints of a single producer/creator. Since several people usually work in a ceramic workshop together, this assumption is somewhat uncertain. However, the biological trends in question were still apparent even though we could not be quite certain whether all the prints on artifacts belong to their respective authors. This could indicate that despite the presence of more than one person in the workshop, the actual molding and shaping of soft printable clay is a one (wo)man show. However, in ancient cultures this may not always be the case, e.g. if the ceramic object is produced during a ritual. Kamp et al. (1999) pointed out that it is likely that certain fingers and finger portions are preferentially represented, in other words the homogeneity of MRB is likely to be caused by similar use of fingers and palms in molding, which may be related to a particular molding process. It is interesting then, that age changes and sexual dimorphism in adults are still perceptible, even though the ceramists used a variety of ceramic clays and molding procedures. If we compare the variability in MRB in adults in our sample with previous research, it does not appear, that the variability increases with greater variety of ceramic clays used.