by Sue Black
The correlation between age and size in young children is reflected in the way we buy their clothes. These are sold by age rather than measurement because manufacturers can predict with some confidence that, say, between birth and six months, a baby will have a head-to-toe height of about 67cms (2ft 2ins). We don’t look for a dress for a 3ft 5ins child, but for a four-year-old. The age range widens as the child grows: baby clothes are labelled in sizes of three-month intervals, then six months. Sizes for toddlers and upwards will rise in one-or two-year increments to the age of about twelve. When puberty strikes, changes to the body make the relationship between age and size far less predictable.
So when we are examining the remains of a fetus or baby, the length of the long bones within the upper limb (humerus, radius and ulna), and the lower limb (femur, tibia and fibula) will allow us to calculate its age to within a few weeks. With a young child we will be accurate to within a few months, and in an older child to within a range of two or three years.
There is a little more to it than simple measurements, however. In children, some bones are comprised of several parts, to allow for growth, which will eventually fuse on maturity. As the pattern of growth and fusion is closely related to age, the stage these bones have reached is a reliable guide. The adult human femur (thigh bone), for example, is a single bone but in children it consists of four different components: shaft, distal articular end (at the knee), a proximal articular head (at the hip) and the greater trochanter on the side of the bone where the muscles attach. The first part of the femur to convert from cartilage into bone is the shaft, which shows bone formation in the seventh week of intrauterine life. The centre of ossification (where bone first forms) at the knee will be visible around birth – indeed, its presence on an X-ray was used in the past as an indicator that a baby had reached full term and that the fetus was therefore considered to be clinically viable. This was important in the prosecution of mothers who concealed full-term births, which carried a harsher penalty than concealing the stillbirth of a fetus.
The bony part of the head of the femur, which forms the hip joint, begins to convert into bone by the end of the first year of life and the top of the greater trochanter, where the gluteus medius and gluteus minimus muscles, vastus lateralis and others attach, appears as a bony centre between the ages of two and five years. Then the different parts start to grow towards each other and eventually fuse.
Between twelve and sixteen years in females, and fourteen and nineteen in males, the head of the femur will fuse to the shaft, followed, within another year or so, by the greater trochanter. The last bit to fuse, to complete the adult bone, is the distal end, at the knee, which occurs between sixteen and eighteen years in girls and between eighteen and twenty in boys. When all the components have fused together there will be no more growth in that bone. When all of the bones finish growing in length, we have reached our maximum height.
The growth and maturity of most bones in the developing skeleton follow a pattern that allows us to estimate a likely age, providing, of course, growth is proceeding as we expect. Some parts of the body offer more information than others. An adult hand, for example, has around twenty-seven bones, whereas in a child of ten these will be made up of at least forty-five separate parts. This makes it a good witness in establishing age in life as well as in death. As it is also easily accessible, and the most ethically acceptable part of the body to expose to the ionising radiation of X-ray, it is often used to determine whether someone presenting themselves as a juvenile for immigration or refugee purposes really is a child.
Over half of the world’s population is born without a birth certificate and therefore no documentary proof of their age. This causes little problem when people remain within a geographical area where the powers that be accept it as commonplace, but when someone who does not have such paperwork migrates to a country where the fabric of society is dependent on official evidence of identity, they can come into conflict with the authorities.
The countries who have signed up to the United Nations Convention on the Rights of the Child agree to protect children from harm, to house them, clothe them, feed them and educate them. When potentially bogus immigrant claimants, or children who have slipped through the net, are identified by the authorities, forensic anthropologists are sometimes asked to assess their age, especially if they come to the attention of the criminal court as either a perpetrator of an offence or a victim, such as a child suspected of having been trafficked.
My colleague Dr Lucina Hackman is one of only two practitioners qualified in the UK to perform age assessment in the living. She uses medical imaging of the skeleton – CT scans, X-rays or MRI – to determine an approximate age which may be brought before the courts as confirmation of the age of criminal responsibility or consent, or as evidence in cases dealing with the international rights of a child.
Once an individual is beyond childhood and adolescence, there is a weaker correlation between age-related features and actual chronological age. We can be reasonably accurate to within five years with people up to about forty years old, but after that changes in the human skeleton are largely degenerative and, to be honest, we all fall apart at different rates, depending on our genes, our lifestyle and our health. We probably all know a sixty-year-old who looks forty, and vice versa. In looking at remains of individuals in their fifth and sixth decades, we tend to resort to descriptions like ‘middle-aged adult’ – I hate that label, especially when it defines me – and when dealing with anyone over about sixty we talk about ‘elderly adults’. Outrageous! It just goes to show how bad we are at assigning age with confidence at the upper end of the scale, whether to a living individual, a dead body or skeletal remains.
So we are adept at determining sex in the adult, less so in the juvenile; quite impressive at establishing the age of a child but mediocre when it comes to grown-ups. What about the other two biological categories, stature and ancestry? One we are really good at and the other pretty poor, by and large. Ideally, the assessment we are best at would be of the most value in establishing the identity of the deceased. Oh, if only nature were so kind! Unfortunately, the one we are really good at, stature estimation, is probably the least important of all four of the biological characteristics.
This isn’t exactly showing the glories of forensic anthropology in the way the television shows do, is it? But in the real world it is important to recognise that if the identity of an individual is not easy to determine, the solution will come down to experience, expertise and probability across all four identifiers. The anthropologist who asserts absolute confidence in the sex, age, stature and ancestry of a skeleton is a dangerous and inexperienced scientist who doesn’t understand human variability.
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In the UK, the height of most adult individuals falls within a range of sixteen inches, between 5ft and 6ft 4ins (1.5m to 1.93m). Anyone outside that bracket might be considered unusually short or unusually tall. The average height for a female is 5ft 5ins (1.65m) and for a male 5ft 10ins (1.78m). Of course, stature is strongly influenced by genetics and environment. If you have tall parents, you will probably be tall, and if they are short you are likely to be short, too. We can predict the adult height of a child either by doubling their stature at the age of two (isn’t it incredible that we grow to half our full adult height within our first two years?) or by calculating what is called MPH (mid-parental height). For a boy, in centimetres, the equation is: father’s height + mother’s height + 13 ÷ 2; for a girl: father’s height – 13 + mother’s height ÷ 2.
To illustrate the influence of genetics we need only look at the variations in average height in different parts of the world. The tallest men are the Dutch, who are on average 6ft (1.83m), and the shortest are from East Timor, at 5ft 3ins (1.6m). Latvia has the tallest women, pipping the Dutch ladies to the post at 5ft 7ins (1.70m), and Guatemala the shortest at 4ft 11ins (1.5m).
The tallest person ever recorded for whose height there is reliable proof wa
s Robert Pershing Wadlow from Illinois in the US, who was 8ft 11ins (2.72m) at the time of his early death at twenty-two. He unfortunately suffered from an excess of human growth hormone, and was still growing when he died in 1940. The record-holder at the opposite end of the scale is Chandra Bahadur Dangi from Nepal, at 1ft 9½ins (54.6cm), a primordial dwarf who enjoyed a long life for those with his condition – he died in 2015 at the age of seventy-five.
As is demonstrated by these examples, genetics is not the only influence on our adult stature. As well as the rarer impact of growth disorders, more commonplace factors such as nutrition, altitude, disease burden, growth variations, alcohol, nicotine, birth weight and hormones will all affect how tall we will be as an adult. With fully favourable conditions, a child will reach their height potential. If they experience adverse conditions in their first fifteen years or so, they are likely to be shorter than expected.
As Western culture views tallness as desirable and shortness as a disadvantage, most of us have a tendency to overestimate our own height. And when we estimate the height of others, we base our assessment on our perception of our own height and so overestimate theirs, too. Unwilling to acknowledge that we shrink with age, we continue through our lives to claim the height we were in our prime, even though we become shorter whether we like it or not. Once we pass forty we lose about a centimetre every decade and, after seventy, a further three to eight centimetres.
Our height is made up of the length and thickness of all of the components of our body, from the skin on the soles of our feet to the skin on the top of our heads, encompassing bone heights and lengths (calcaneus, talus, tibia, femur, pelvis, sacrum, twenty-four vertebrae and skull), plus joint spaces between these bones and also the thickness of the cartilage between the bones of each joint. With age, cartilage thins and some of the joint spaces collapse. Clinical conditions such as arthritis and osteoporosis will also alter the bones and joints and reduce overall height. And believe it or not, our height varies according to the time of day: we are on average half an inch shorter by the time we go to bed than we were when we got up. We lose most of that height within three hours of rising, as our cartilages settle and compress and decrease our joint spaces.
It would be quite a challenge if, when trying to determine the height of an individual from a skeleton, we were to attempt to add together the measurements of all the different bones, cartilage and spaces that contribute to it. When a body is found with all the bones pretty much where they should be, there will be a lot of soft tissue still present, so we will get out our tape measure and record the recumbent stature there and then. In the mortuary, we will follow the same procedures as we do to calculate the age of a child from their long bones. It stands to reason that if you have long arms, and especially if you have long legs, you will be tall and the opposite is also true. We measure the length of each of the twelve long bones (the femora, tibiae, fibulae, humeri, radii and ulnae, of which we have two apiece) on a device called an osteometric board and place the values into appropriate statistical regression formulae for the sex and ancestry of the individual. The resulting living stature will be estimated to within about three or four centimetres of the person’s living height.
The reality is, though, that in a forensic investigation, stature is unlikely to be a major identifying feature in its own right unless you are exceptionally tall or small. I have known of families who have latched on to the vain hope that remains we have examined are not those of their son, even questioning a DNA result confirming his identity, purely because they have been given a most likely height of around 5ft 6ins and he was actually 5ft 7½ins. That is why we provide the full margin of error and suggest a range.
Our fourth biological identifier is ancestry, or what may in the past have been called ‘race’. We now avoid this more emotive term because of its negative associations with social inequalities, and the risks such connotations carry of preconceptions and misconceptions, and also because the biological evidence for which we are looking is of a long-past origin. Assignation of ancestry is potentially of enormous interest to the investigative process but often forensic anthropologists are not talking the same language as the police. What the police will want to know is whether they should speak to members of, say, a Polish or a Chinese community. Unfortunately, we are unable to distinguish between groups such as these and others of close biological proximity just from looking at skeletal remains.
We categorise people on the basis of a variety of physical traits: the colour of their skin, their hair or their eyes, the shape of the nose or eyes, the type of hair they have or their language. Clusters of multi-locus genetic data have largely confirmed the accepted premise that, notwithstanding a bleed of features across geographical regions, we used to be able to genetically separate the world into four basic ancestral origins. The ‘out of Africa’ concept, which classified the first ancestral group as people originating from sub-Saharan Africa, still holds firm. The second group stretched from North Africa across Europe and east to the border with China. The third encompassed the eastern regions of the Asiatic land mass and, across the North Pacific Ocean, the North and South Americas and Greenland. The fourth, more geographically isolated, region consisted of the South Pacific Islands, Australia and New Zealand. This resulted in the four archaic classifications of Negroid, Caucasoid, Mongoloid and Australoid.
While we may quite easily categorise the origins of our ancestors, things have become trickier in the more recent past and I suspect many of us would get a few surprises regarding our own histories if we investigated our genes. In our palaeo-distant pasts, it is likely that cross-linkage between these groups was limited, but in our smaller, modern world, where interactions have been more common and more frequent over the generations, the genetic signal for each of the four discrete classifications is becoming ever fainter.
What genetics cannot tell us with any reliability is the difference between a man from China and a man from Korea, or a British woman and one from Germany. Therefore it is of no value whatsoever in assisting us with assessing the ancestry of a person descended, for example, from an Indian maternal grandfather, English maternal grandmother, Nigerian paternal grandfather and Japanese paternal grandmother.
There are some basic characteristic differences, particularly in the facial region of the skull, that can be detected in individuals in whom the manifestations of ancestral origin are more protected. We do have computer-based systems that can process a variety of skull measurements and give us suggestions as to the most likely ancestry for an individual, but these must be viewed with some caution. What we will be hoping in such circumstances is that hair or other soft tissue survives that can assist us, or that clues may be provided by personal effects such as clothing, documents or religious jewellery. DNA analysis is our best chance but it will only tell us about ancestral origin, not nationality. It cannot tell us whether a person of Indian ancestry was born in Mumbai or London. Only stable isotope analysis offers us any help here.
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Once the four biological parameters have been determined, our next job is to find individual identifiers that will enable us to focus on a single person to the virtual exclusion of all others, using one or all of the INTERPOL-approved primary methods: DNA comparison, dental records or fingerprints. Fingerprints are unlikely to be obtainable from skeletal remains but it is sometimes possible to retrieve them from even quite badly decomposed bodies.
If DNA databases provide no matches, the police may go public with the information to try to generate leads. To establish the personal identity of the deceased – their name – we need intelligence to follow, and it is hoped that the community will respond with suggestions that can be eliminated or pursued further by investigators. When the police put out the message that the deceased is, say, a male aged between thirty and forty, around 5ft 8ins in height and black, they are obviously narrowing the range of possibilities by ruling out females, children, old people, the short, the tall and the other umbrella
ancestral groups. But there will, as discussed previously, still be thousands of individuals registered as missing who will fit that broad biological profile.
Missing person posters circulated by the police will probably include an image of what the person may have looked like based on a reconstruction of their face, like the one that helped to identify our woodland suicide in Chapter 2. The forensic artist or reconstruction expert will rely on the biological characteristics that we have provided being correct. If we say the body is that of a woman when it is a man, or we say they are black when they are white, or around twenty years old when they are more like fifty, then the reconstructed face is never going to resemble the person it should depict.
An illustration of how dramatically these reconstructions can help to accelerate identification is provided by a 2013 Edinburgh case in which dismembered female remains were found in a shallow grave on Corstorphine Hill. The only clues were some distinctive rings on the fingers and some extensive dental work. A likeness produced by my craniofacial colleague Professor Caroline Wilkinson and circulated internationally was recognised by a relative in Ireland as Phyllis Dunleavy from Dublin. Mrs Dunleavy had been in Edinburgh staying with her son, who had claimed she had returned to Ireland. The identification led to him being charged with her murder within a month of the discovery of the body, and subsequently convicted.
The shorter the time between a death, the deposition of remains and the identification of the deceased, the greater the potential for retrieval of evidence will be. In this case, the speed with which the body was identified unquestionably enhanced the investigative process and was key to the success of the prosecution.