Written by Etta Coleman

“Age” in itself is a relative term: it can refer to how many years have passed since birth, known as chronological age, or it can reference the toll environment and genetics have taken on the body. The former is the most common conception of an individual’s age during assessment. However, lifestyle also alters the human body, particularly during later life. Whether it be work habits, lifestyle choices, dietary habits, or substance use, each individual’s body reacts and adapts uniquely to its set of physical circumstances. This results in ageing more or less quickly than is considered typical for the chronological age category, which can lead to potentially skewed age estimations when using the chronological age category, since osteologists are actually assessing how well the individual’s skeleton has resisted degradation. This is known as biological age.

Assessing age at death is a crucial part of building demographic profiles both for individuals and for the wider population. Age estimates are commonly employed to plot the mean age-at-death of a population in order to determine fertility rates, mortality rates, and the extent of pathological intensity. By misinterpreting an individual’s age at death, these profiles are in danger of wildly misrepresenting past populations and influencing the way we view the evolution of disease and health today. In order to fully understand the issue at hand and how it can be mitigated, this article strives to lay out standard methods of ageing and how the markers under assessment may be influenced by external factors. It will also discuss potential solutions to this issue, and how future research should move forward.

It is important to note here that many methods of age estimation are developed for use on communities from the medieval period and earlier, as the industrialisation of the world was accompanied by a vast change in the alteration of the skeleton. For example, the introduction of softer, processed foods across the globe during the industrial revolution minimized occlusal tooth wear, rendering archaeological age-at-death analysis unsuitable for modern populations. There are alternative methods of ageing that are developed for more recently deceased individuals, but they are typically utilised in forensic cases, and will not be discussed here. Traditional osteological assessment of age takes place under macroscopic examination of several key elements of an individual’s skeleton. The primary locations in the body which are utilised for age estimation are: the cranium, pelvic region, dentition, and ribs. These analyses are often reliant on assessment of the extent of degeneration in these areas as a baseline for age. Because the skeleton is still in the process of ossifying until roughly the age of 25, age estimation of juvenile remains is relatively straightforward. Thereafter, age estimation is reliant on the degradation of certain parts of the body, and the relative rate at which this is purported to happen.

Issues arise with these techniques when the resultant age estimates are proposed as a chronological age at death. Because the elements under investigation are also very prone to alteration by behavioural, dietary, occupational, and genetic factors, the assessment of age against a standardised concept of the way a person’s body should age is more reflective of the biological age – how old their skeleton is in relation to the “normal” – than chronological age. In addition to this, taphonomic damage and differential preservation cause some estimations to be wildly skewed, as the elements required to estimate age may be heavily eroded post-mortem, or even lost in the depositional process.

In recent years, more attention has been paid to this issue, and several studies have been undertaken which aim to determine how detrimental to ancient demographic studies it may be to not distinguish between chronological and biological age when performing estimates and generating demographic statistics.

Couoh found that the difference between chronological age and biological age in modern populations can be as much as 10 years. In ancient populations, this error range is likely even higher. Focus on chronological age has allowed the oversimplification of adult individuals, and the subsequent erasure of very old individuals because of the lack of definitive skeletal traits. Appleby proposes that numbered age estimates be done away with completely, so as to focus on the ageing process of the human body within archaeology and its relationship to its environment. Not only do the very old contribute to demographic profiles and mortality plots, but analysis of their remains can also contribute to our understanding of social structure, and cultural practices surrounding ageing. In most age estimation models, the oldest category available for scoring is 60+ years of age. By continuing to utilise numbered age ranges and estimates, bioarchaeologists may be contributing to the growing estrangement of chronological from biological age. Focusing more on the ways in which the body ages within a society, and understanding the forces, both internal and external, that contribute to skeletal and biological ageing, will hopefully result in a more inclusive view of age in the time of osteology, as well as a better understanding of demographic structure in ancient societies.

It can undoubtedly be said that the attempt to identify the chronological age of an individual is helpful in several ways, not least of which is tracking premature ageing and identifying the reasons behind the acceleration of the ageing process. In the same way, it helps to identify individuals who have aged particularly well, although this is much more rare in bioarchaeological contexts. On the other hand, chronological age estimates can help to identify the progression and stages of terminal diseases, including the effect they have on the skeleton. In this way, chronological age can be compared against biological age to great effect. Overall, especially in “healthy”  individuals, it is more harmful than positive to only account for chronological ageing. In any case, chronological age should always be assessed in addition to, and separately from, biological age. Whether true chronological age estimation is realistic, possible, or reliable, remains to be seen.

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Bibliography

Appleby, Jo. 2018. “Ageing and the Body in Archaeology”. Cambridge Archaeological Journal 28 (1): 145–163. doi:10.1017/S0959774317000610.

Couoh, Lourdes R. 2017. “Differences between Biological and Chronological Age-at-Death in Human Skeletal Remains: A Change of Perspective.” American Journal of Physical Anthropology 163, no. 4: 671–95. doi: 10.1002/ajpa.23236.

Gowland, Rebecca. 2009. “Ageing the Past: Examining Age Identity from Funerary Evidence.” Essay. In Social Archaeology of Funerary Remains, 143–54. Oxford, UK: Oxbow Books.

Gowland, Rebecca. 2007. ‘Age, ageism and osteological bias: the evidence from late Roman Britain.’, Journal of Roman archaeology; supplementary series, 65. pp. 153-169.