Age Determination in Human Beings
Age determination is an important aspect of forensic anthropology which helps in establishing the biological profile of an individual. Age classifies the persons in different groups which helps in limiting the area of investigation.
The methods usually involved in age estimation are based on the principles of forensic anthropology and are applied on deceased. However, there are certain methods which can be applied to living beings too. This article is based on the age determination of the deceased.
Determination of Age in Humans
If the particulars like birth records, identity proofs, etc. are found on the crime scene or with the deceased, then it is quite easy to determine the age of that person.
If the body is not decomposed or mutilated then by observing the morphological characteristics like the secondary sexual charcteristics, old age characteristics, etc. can be helpful in determining the age of the deceased.
For example, development of breasts and pubic hair in females whereas fine downy hair growth on the pubis and face in males are signs of puberty(age between 12-18 years). Loose skin, wrinkles on the face, arcus senilis in the eyes are the signs of old age(40 years and above). The height and weight measurements of the deceased are also helpful in estimating the age.
If the body is decomposed or mutilated, then the most effective methods applied in age estimation are the dental records and bones examination. The height and weight of the skeletal remains can be helpful in age determination.
Methods to Determine Age
1. Dental Records
The development of teeth in human beings is age dependent. The dentition of Homo sapiens is diphyodont and heterodont. Diphyodont means the detention gives rise to two sets of teeth- temporary teeth(deciduous teeth/milk teeth) and permanent teeth(adult teeth).
Heterodont refers to the dentition in which different types of teeth are found- incisors, canines, premolars and molars.
Dental records include the information about the two sets of teeth, the time of eruption of the teeth and their root calcification.
The two sets of teeth differ in their number, size and shape. The temporary teeth are 20 in number- 4 incisors, 2 canines and 4 molars in each jaw. They are small in size, delicate, narrow and light. The colour of the teeth is china-white. Molars are large with flat crowns and small divergent roots.
The permanent teeth are 32 in number- 4 incisors, 2 canines, 4 premolars and 3 molars in each jaw. They are comparatively large, heavy, broad and strong. The color of the teeth is ivory white. Molars are smaller with cusps on the crown and bigger straight roots.
The time of eruption of teeth is a good indicator of age till 18-25 years. Temporary teeth start erupting generally from 6 months after birth and continue till the age of 20-30 months(2 to 2 and half years). The sequence of eruption of temporary teeth is: central incisors(lower) → central incisors(upper) → lateral incisors(upper) → lateral incisors(lower) → first molars → canines → second molars.
The eruption of permanent teeth starts from the age of 6-7 years and continues till the age of 14-15 years. The sequence of eruption is: first molar → central incisors → lateral incisors → first bicuspid → second bicuspid → canines → second molars. The third molars, also called wisdom teeth which erupt between the age of 17-21 years and the last one to complete the dentition.
Root calcification is also an indicator of age and refers to deposition of calcium in the roots of the teeth. In temporary teeth it begins at the age of 1½-2 years and is completed till 3 years of age. While in permanent teeth the calcifican starts at the age of 9-10 years and continues till the age of 18-25 years of age.
The above mentioned information is obtained from the X-ray examination of teeth. These methods estimate the approximate age of an individual and cannot estimate the age above 25 years.
There are two methods of age estimation based on dental examination. They are Gustafson’s method and Boyde method.
- Gustafson’s method includes the microscopic examination of the longitudinal section of the central part of the tooth. This shows the changes in the teeth due to wear and tear with advancing age. The changes are categorised into 6 groups- attrition(gradual wearing of teeth) → periodontosis(loosening of teeth) → secondary dentition(in filling of normal root cavity)→ cement apposition(increase in tissue holding tooth in place) → root resorption → root transparency. This method is helpful in age estimation between 25-60 years.
- Boyde’s method is based on the incremental lines which can be seen in the histological section of teeth. These are also called neonatal lines, which are formed at birth and increase in number till death. Counting these lines can give the accurate age of an individual.
2. Ossification of Bones
It is referred to the fusion of ossification centres of the bones which is age dependent. The changes are studied by the means of X-rays. There are various ossification centres in the skeletal system categorized as primary and secondary ossification centres.
Primary centres are the one where the bones start their formation and are usually the long bones. Certain bones have multiple centres of ossification which are responsible for secondary ossification. The ossification centres are found in- skull, vertebral column, sternum, ribs, pectoral and pelvic girdles, upper limbs(elbow, wrist and phalanges) and lower limbs(knee, ankle and phalanges).
Ossification of bones starts immediately after the birth of the infant and continues till the age of 25 years. After 25 years of age there are few specific regions of the skeleton which can indicate the approximate age of an individual till the age of 60 years.
Closure of Skull Sutures– The closure of fontanelles and sutures of the skull are great indicators of age of an individual. The fontanelles the first one to close which begins at the age of 2 months and completed till the age of 3-5 years. The sutures started closing at the age of 2-3 years and completed till 60 years of age. The sequence of suture closure- metopic sutures(2-3 years) → basioccipital-basisphenoid(18-21 years) → sagittal(25-40 years) → lambdoid(25-45 years) → coronal(25-60 years).
Age is a crucial factor in biological profiling of the deceased. There are various methods developed to estimate the age of an individual as mentioned above in the article. But still there is a need to refine the existing methods and develop the new ones to aid the accurate age estimation.