Estimation of Gender from Human Skeletal remains

Estimation of gender from skeletal remains is another major aspect that a forensic anthropologist deals with. Determining gender precisely using anthropological evidences like skeletal remains delimits the area of investigation and guides the investigator on the right track as to whether the cadaver belongs to a male or female human. Since human beings exhibit sexual dimorphism i.e. different characteristics apart from sexual organs within the two sexes of same species, there are numerous conspicuous variations in male and female skeleton.

The differences in skeletal structures, form, length and weight of bones comprise some of these notable distinguishing features that help a forensic anthropologist to conclusively estimate whether a skeleton or bone sample belongs to a male or female human. The differences in skeleton forms of the two sexes in humans is due to an altogether slightly different mode of development that occurs due to varying hormonal secretions from the onset of puberty, also a reason being adaptations for parturition in adult females.  

Pelvis, skull, ribs and sternum are the major bases that provide grounds for distinguishing male and female skull. Numerous researches have stated that a distinction between male and female skull based on pelvis provides the highest accuracy (about 98%) followed by skull whose accuracy of results is limited by the factor of age as some of the features on which the comparison is based are not developed till the age of 18-20 years. Let us discuss the major features that can be used to estimate the gender from human skeleton or a part of it:

1-Pelvis 

Pelvis provides the most accurate ground of sexual dimorphism. If a pelvic remain is found at the crime scene, as a whole or in part it can be used to estimate the gender with great degree of certainity. Basic differences that can be seen between male and female pelvis are summarized in the table below:

Picture 1: Male pelvis 
Picture Reference : Source

Picture 2: Female pelvis
Picture Reference : Source

2-Skull 

Sex determination using examination of skull features is highly accurate, but slightly than that provided by pelvis. Hence, sex determination using features of skull is coupled with the data provided by pelvic examination and the combined accuracy ranges up to 99%. Some of the features of skull that distinguish males and females are summarized in the table below:

Picture 3: Male skull (left) vs Female skull (right)
Picture Reference : Source

3-Dimensions of long bones

An alternate method of sex determination involves the measurement of various dimensions of long bones on the basis of which it is estimated whether the bones belong to a male or female. This method is useful in cases where limited number of bone samples are recovered from the crime scene, but there is a limitation that bone samples should be that of long bones like humerus, radius, ulna, femur, tibia, fibula etc., also the dimensions of long bones are subjective to the type of population, race, nutrition and various other factors. The accuracy of gender estimation from this method ranges from 60-90%. Various anthropometric measurements of bones are taken on the basis of which sex determination occurs. These measurements of various bone samples are summarized in the tables below on the basis of researches conducted in the past:

1. Humerus (Indian bone samples)

1. Radius

1. Ulna

1. Femur

1. Tibia

1. Pelvic measurements (right pelvis)

4-Sternal end of 4^th Rib

When it comes to sex determination using bones, skull and pelvis are the first choice as gender estimation using these specimens is easy and highly accurate. However, it is not always necessary that two of the above-mentioned samples are always found, or if found, are in a state that they can be used to determine gender. Sex determination using 4^th rib is another tool that can be used for gender estimation in cases where fragments of ribs are found at the scene of crime. An advantage of this technique is that it offers a good degree of accuracy with an additive that its accuracy increases with the age of samples recovered. This also indicates that the technique can be conveniently used for samples that belong to higher age group. The accuracy of the technique ranges up to 94%. The technique is based on the principle of bone decalcification as the age increases and involves comparison of osteometric measurements to determine sex. Some of the measurements are:

1. Maximum superior inferior height (SI)
2. Maximum anterior posterior width (APW)
3. Maximum pit depth (PD)

The mean values of the above-mentioned parameters are summarized in the tables below for different age groups:

1. 16-30 years (accuracy 61.8%)

1. 31-45 years (accuracy 84 %)

1. 46-60 years (accuracy (94%)

*All the measurements are based on researches, these do not display the absolute value that a bone sample recovered will display if measured for the same parameter.