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Age estimation

Estimation of the age of a person at death from skeletal remains has been studied many times (Stewart and Trotter 1954; Krogman 1962; Stewart 1979; Bass 1987; White 1991). Numerous techniques are available to the forensic osteologist, allowing age to be estimated with varying degrees of accuracy (Bass 1987). Presented below is a review of the most common and reliable techniques available for age estimation.

Estimation of age from the juvenile skeleton

In juvenile skeletal material, age estimation is best determined from the state of dental formation and eruption (Moorees et al. 1963a; 1963b; Demirjian et al. 1973; Gustafson and Koch 1974; Anderson et al. 1976). In cases where no cranium or mandible can be found, long bone length (Ubelaker 1989) and epiphysial union (McKern and Stewart 1957) observations provide the best estimations (Stewart 1979; Krogman and Iscan 1986; Ubelaker 1987).

1. Estimating juvenile age from the dentition

Eruption and wear of teeth play an extensive role in the determination of age in a juvenile skeleton. Tooth eruption is more closely related to chronological age than the development of most other skeletal parts, and seems to be under 'tighter genetic control' (White 1991).

2. Estimating juvenile age from long bone length

In the absence of teeth and other epiphysial indicators, juvenile age can be estimated by the diaphysial length of long bones. However, these procedures should always be applied to the same population from which the techniques were derived. Ubelaker (1989) lists comparative data useful in the age assessment of juvenile long bones.

3. Estimating juvenile age from epiphysial closure

The fusion of postcranial epiphyses is an orderly process and, if evident, can provide the forensic osteologist with the means of estimating the minimum and maximum possible age brackets. This is done by making as many observations as possible of the state of epiphysial closure in the skeleton. It is important to note that although each epiphysis is observed to fuse at an average known age, the exact timing varies by individual, sex, and population (White 1991). The metabolic state of the individual is also known to affect the rate and timing of epiphysial closure (Wood pers. comm.). When all epiphyses have fused, usually under the age of 28, growth ceases. As a result, fewer age indicators exist for the postcranial skeleton in the adult. McKern and Stewart (1957) provide an extensive summary of the various ages and rates for epiphysial fusion. Other authors have described similar tables detailing epiphysial closure (Stevensen 1924; Mensforth and Lovejoy 1985; Webb and Suchey 1985; Krogman and Iscan 1986).

Estimation of age from the adult skeleton

Several techniques are also available for the determination of age from the adult skeleton. These methods include examination of the adult dentition (Lovejoy 1985; McKee and Molnar 1988), the pubic symphysis (McKern and Stewart 1957; Suchey et al. 1988), the sternal rib (Iscan and Loth 1986), closure of cranial sutures (Meindl and Lovejoy 1985; Krogman and Iscan 1986), and the auricular surface of the hip bone (Lovejoy et al. 1985). Brief summaries of each are provided below.

1. Estimating adult age from the dentition

Estimation of age from the adult dentition is based on tooth wear. The rates and patterns of wear are governed by tooth development sequences, tooth morphology and size, internal crown structure, tooth angulation, non-dietary tooth use, the biomechanics of chewing, and diet (McKee and Molnar 1988; White 1991). The rate of wear has been shown to be reasonably homologous within a population (Lovejoy 1985), and it follows that the extent of such wear is a function of age. Lovejoy (1985) states that dental wear is the best single indicator for determining age of death in skeletal populations.

2. Estimating age from the surface of the pubic symphysis

Certainly amongst the best, and most widely used, methods for determining the age of an unknown adult skeleton, is by examination of the surface of the pubic symphysis (McKern and Stewart 1957; Suchey et al. 1988). Specific age-related changes continue to be expressed in this region after the individual has reached full stature, and epiphysial closure is complete (White 1991). Although a large amount of variation exists between individuals and populations, representative examples of symphysial changes have been published. Ten phases of pubis symphysis modification are described (Todd 1920; McKern and Stewart 1957; Gilbert and McKern 1973; Reichs 1986; White 1991). These phases describe specific patterning of ridges, grooves and ossification nodules on the surface of the pubic symphysis, and standard casts are available for comparison with an unknown individual. There is no intact pubic symphysis in the Pandora collection to utilise this technique.

3. Estimating adult age from the sternal rib

Iscan and Loth (1986) have studied metamorphosis of the sternal end of the fourth rib and found that these changes can be used to assess age but not sex. They define a series of phases, similar to those given for the pubic symphysis, that describe set characteristics of the rib. This method, however, relies on the presence of a fourth rib in good condition among the remains (White 1991). Standard casts are available for the comparison with an unknown individual.

4. Estimating adult age from cranial suture closure

It has been appreciated since the 1500s that the various cranial sutures progressively fuse, from the internal surface outwards, with increasing age (White 1991). This field, however, is largely discredited for use in estimating adult skeletal age. Meindl and Lovejoy (1985) revised this method, but its reliability is yet to be proven.

5. Estimating adult age from the auricular surface of the ilium

Lovejoy et al. (1985) examined the auricular surface of the ilium in an attempt to correlate its features with chronological age. They describe age-related changes in surface granulation, microporosity, macroporosity, transverse organisation, ridging, and striations similar to those described of the pubic symphysis. Lovejoy et al. (1985) note that this method is less reliable than techniques based on the pubic symphysis.

Other techniques for age estimation of the adult skeleton have been developed, including microscopic analysis of cortical bone (Simmons 1985; Frost 1987; Ubelaker 1989). The consensus remains that age determination from a juvenile, or adult, skeleton must be multifactorial if a satisfactory determination of age at death is to be achieved. Often the techniques used depend on what skeletal material is available.

For the Pandora skeletal material, age estimation was largely concluded from the state of epiphysial union and the extent of dental attrition. The best techniques for estimating adult age come from the observation of pubic symphysial surface and were not applicable to this collection of remains. Osteological characteristics used for age, estimation and the conclusions drawn for each individual are summarised below.

Age estimation for Tom

Tom's skeletal remains consistently demonstrated incompletely fused epiphysial plates on numerous bones. In some cases, the state of fragmentation was accelerated due to epiphyses separation. Clearly, Tom was younger than both Dick and Harry. A summary of epiphysial closure stages is provided in Table 1. Included in the table is the degree of fusion observed and the estimated age (McKern and Stewart 1957; Rathbun and Buikstra 1984; Bass 1987).

Table 1: Stages of epiphysial fusion evident on Tom's skeletal remains

The stages of epiphysial union seen in Tom's remains most strongly indicated his age to be somewhere between 15 and 19 years. Estimation of age could also be performed on the state of dental attrition on teeth from the maxillary fragment and mandible. Using data from Lovejoy (1985), the degree of occlusal wear indicated an age of about 20 to 24 years. This figure is slightly higher than was indicated by the postcranial skeleton, which could be due to excessive tooth wear as a function of the diet. Microscopic analysis of the teeth showed an extensively scratched occlusal surface which would support this theory (labial surfaces of the teeth were unmarked). In summary, Tom's age was most accurately determined by the various stages of epiphysial fusion and was estimated at 17 +/-2 years at the time of death.

Age estimation for Dick

Amongst the remains of Dick, few incompletely fused epiphyses were found which could be used to estimate age accurately. However, eliminations could be made considering many epiphyses were already fused. These data are summarised in Table 2. Included in the table is the degree of fusion observed and the estimated age (McKern and Stewart 1957; Rathbun and Buikstra 1984; Bass 1987).

Table 2: Stages of epiphysial fusion evident on Dick's skeletal remains

The stages of epiphysial fusion indicate Dick was aged somewhere between 20 and 26 years at the time of death. The incompletely fused distal radius was examined by X-ray, and was the only epiphysis incompletely fused. This bone provided a more reliable estimate. The dental attrition was examined from the mandible, and using data from Lovejoy (1985), age was estimated between 24 and 30 years of age. In summary, observations indicate Dick's age at death to be approximately 22 +/-3 years. This figure is supported by the analysis performed by Wood and Hodgson (1996) on the original skeletal material from Dick, who also estimated age at 22 +/-3 years.

Age estimation for Harry

Examination of Harry's skeletal remains showed no indication of incompletely fused or unfused epiphyses. This feature reduced the reliability of age estimation. The data are summarised in Table 3. Included in the table is the degree of fusion observed and the estimated age (McKern and Stewart 1957; Rathbun and Buikstra 1984; Bass 1987).

Table 3: Stages of epiphysial fusion evident on Harry's skeletal remains

Age estimation was not possible from the clavicle because of its fragmentation. In addition, the basi-occipit of the cranium was completely fused, indicating an age greater than 19 years.

To provide a better estimate of age, the state of dental attrition on the skull was examined. Using data from Lovejoy (1985), age was estimated from the dentition at 24 to 30 years. It was difficult to determine the rate of dental wear, however, since the occlusal plane between the mandible and cranium was considered abnormal. This angulated plane was caused by the underdeveloped nature of the maxilla and may have led to a reduced wearing of the teeth through the restriction of medial-lateral mandibular movements. However, a forensic odontologist was consulted who agreed with the postcranial age estimate. The internal cranial sutures were examined and found to exhibit the first signs of fusion. This alone might place the individual in his early thirties (Krogman and Iscan 1986).

In summary, the precise age estimation of this skeleton was difficult and unreliable. This was primarily because of the abnormal developmental state of the skull, the absence of an intact pubic symphysis, and completely fused epiphyses. It is the authors' opinion that Harry was aged approximately 28 +/-4 years.

It is important to remember that the individuals to whom the Pandora skeletons belonged were born approximately 230 years ago, and cannot be assumed necessarily to parallel a modern-day population. Many of the current techniques available for age determination from epiphysial union were derived from skeletal populations of early last century.

People of today are known to mature earlier physically, and at a faster rate than populations over two centuries ago (Wood pers. comm.). Clegg (1968) states that over the past 150 years, English schoolboys have shown a steady increase in height at any age, due to an increased rate of growth during childhood. Furthermore, this trend is not confined to any one country or continent (Tanner 1962). This results in modern-day individuals attaining a greater height and an earlier rate of epiphysial fusion than populations of the 18th and 19th centuries. Therefore, it should be noted that the approximate ages given for Tom, Dick, and Harry are probably slightly underestimated.

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