Sex Determination from Skeletal Remains

Introduction

One of the first biological characteristics determined from the adult bones is a person’s sex. Because some methods for determining other differentiating characteristics, such as age at death and size, are gender-specific. Furthermore, knowing the sex of a deceased person eliminates a huge percentage of possible identifications in the forensic area.

Although several macroscopic methods for determining the sex of infant and juvenile skeletal remains have been developed, current standards generally recommend that this is not attempted. This is because the procedures have been demonstrated to be unreliable when used on skeletons from various times and locations. DNA analysis and peptide analysis can be used to determine the sex of children.

The sexually dimorphic traits of skeleton size and shape are examined to determine sex. The combination between heredity, hormonal fluctuation, culture, and environment causes differences in male and female skeletons. Sex determination of skeletal remains is considered reliable for individuals who have reached skeletal maturity. It’s important to note, though, that skeletal traits aren’t necessarily polarised in terms of sexual dimorphism – skeletons can’t always be divided into neat categories. Instead, sex-determining features are found on a spectrum ranging from very feminine to moderate to very masculine.

Biological characterization based on Sex

Sex is a discrete variable in the normal living and yet fleshed dead – one is either male or female. In the skeleton, where both morphologic and metric manifestations combine to produce a continuum, differences between the sexes are significantly less distinct. For example, there is no exact size above which all men are male and below which all women are female. Again, if the adult skeleton is complete or at least has an intact pelvis, sex can usually be determined with 100% accuracy.

Although primary sexual features (e.g., external genitalia) are present in the soft tissue before birth, no such definitive marker has yet been identified in the skeleton. Although sex differences in immature skeletons have been quantified, they remain minor until secondary sex characteristics develop during adolescence. Measurements of growth-based differences between males and females have been used to try to sex prepubescent bones, but the results are far from definitive.

Sex determination by the human pelvis

The simplest and most accurate way to determine sex in an adult is to examine the pelvis morphologically. The most sexually dimorphic part of the skeleton is the pelvic girdle. It has a high degree of accuracy when it comes to determining sex. The primary cause of sexual dimorphism of the pelvis is reproductive mechanics. It does not become apparent until adolescence.

The male pelvic region is larger and more robust than the female pelvic region in terms of overall appearance. The hips are more vertical in males than the female. The coccyx is located at the back of the pelvis. The male coccyx is larger than the females. The angle at the front of hips where both sides join is obtuse in the female, and closer to ninety-degree in the male. The pubic bones and sciatic notch are wider in females, resulting in an obtuse sub-pubic angle and a more open pelvic inlet to facilitate childbirth. The male pelvis is narrower. It is constructed only for support and locomotion. Thorough knowledge of cranial morphology can allow experts to approach 90 to 95% accuracy.

 MaleFemale
Pelvis as a wholeThick, heavy, markedly muscularSmoother, lighter, more spacious
ShapeHeart shapedCircular or elliptical
Body of pubisTriangular shapeQuadrangular
Sub pubic archInverted V-shapedInverted U shaped
Greater sciatic notchDeep and narrowBroad and shallow
Sacro iliac jointLargeSmall
sacrumLong and narrowShort and wide

Five features in innominate that indicate sex in the pubic region are;

  1. Width of the sciatic notch [inferior ilium]
  2. Subpubic angle [concavity]
  3. Ventral arc [on the pubis, near the symphysis, ventral]
  4. Ischiopubic ramus [bone connecting pubis and ischium]
  5. Acetabulum diameter [lateral innominate]

However, because sex-related features differ from one group to the next, the observer must be familiar with population-specific variances. Males, on the other hand, have rougher bones with larger crests and ridges, which are frequently used as muscle attachment points. New research has led to the discovery that the mandible alone is near as sexually dimorphic as a complete pelvis. In adult males, it has been observed that the posterior ramus has a distinct angulation or flexure at the level of the occlusal surface of the molars, while females retain the straight, juvenile configuration.

Quantification of size differentials sometimes allows a reasonable degree of separation of the sexes. Although there are several metric techniques from the skull and pelvis, this type of analysis is especially useful in long bones where morphological differences are not obvious. Even within the three primary race groups, discriminant function formulae have been calculated using the dimensions of several bones and their substructures, although these methods are largely population-specific.

Asian Indians, for example, are Caucasoid, although they are shorter and gracile than white Americans or Europeans. As a result, if American standards are utilized, most Indian males will be misdiagnosed as females. Interestingly, head diameter, shaft circumference, and distal epiphyseal breadth are frequently better discriminators than the total length of a long bone.

Skeletal biologists have been looking for evidence of childbearing in the pelvis for many years. Angel scientists knew that both pregnancy and parturition are associated with tearing and reattachment of the ligaments on the dorsal surface of the pubic bone. He reasoned that the degree of scarring caused may be used to calculate the number of births. Houghton (1974, 1975) and Dunlap (1981) supported this concept and applied it to the pre-auricular sulcus. However, further observations have revealed similar pitting in childless females. It is leading to the conclusion that other factors may also be responsible for these formations.

Sex determination by Human skull

In an adult, the simplest and most accurate determination of sex can be done by the human skull.

Difference between Male and Female Skull

  • General size

The Size of the masculine skull is larger whereas the female skull is comparatively smaller than the male skull.

  • Structure

The male skull is rugged or rough and the female skull is smooth and gracile.

  • Supraorbital ridges

It is the region that is directly above the orbit and nose of the brow ridges.

  • Orbits

The male orbits are squarish with rounded margins and in females, it is distinguished by roundish shape and sharp margins.

  • Frontal bone

the forehead is known as the frontal bone. In males, the skull forehead is steeper or sloping whereas in females it is more vertical and rounded.

  • Glabella

It is the point between eyebrows where females use to put kumkum/tika/bindi in Indian culture. In males, glabella is well developed and ill-developed in females.

  • Zygomatic arches

It is the bony arch below the eye socket, formed by fusion of the cheekbone and the zygomatic process of the temporal bone. It is the special characteristic that is more pronounced or robust and tends to extend in males and whereas in females it is less pronounced and tends not to extend beyond the external auditory meatus.

  • Mastoid process

It is located on the inferior portion of the temporal bone, just posterior to the external auditory meatus. In males, it is larger and massive but in females, it is smaller and more pointed.

  • External occipital protuberance

It is the prominent feature of the masculine skull it shows good development whereas in females it is less developed.

  • Maxillary bone (cheekbone)

In males, it shows a more massive, heavier appearance and is placed more laterally and in females, it is slender, lighter, and more compressed.

Sex determination from Mandible

Mandible is not a part of skull. It is attached to skull with the help of cartilage materials.

ParameterMaleFemale
ChinSquare shapeRounded shape
Height of body of mandibleMore in malesLess in females
Ascending ramusBroadLess broad
Condyloid processMore massive in malesLess massive in females
GonionEverted in malesInverted in females
Anatomical angleMore acuteMore obtuse

Biological Characterization based on Race

Race can be considered as a rough classification system for biological characteristics. Caucasoid, Mongoloid, and Negroid are the three major race categories to which most people belong.

However, there will always be equivocal cases because of admixture. Moreover, there is a great deal of variation within each group, and skin color is only one aspect of racial classification. Swedes, Italians, Egyptians, and Asian Indians look very different but are all skeletally “white” even though some Indians may have dark brown skin.

Finally, even if a skeleton is Caucasoid, there is no skeletal indicator of soft-tissue features such as eye color or hair form. In the skeleton, craniofacial morphology is the best indicator of racial phenotype. Black people have a long, low, narrow skull with alveolar prognathism (forward protrusion of the jaws) and a wide, flat nose with smooth sills. A high, round, or square cranium, an orthognathic or straight face, and a long, narrow, projecting nose with sharp sills characterize whites.

It must be kept in mind that these are archetypal or ideal descriptions and many variations within each group overlap with the others. It’s also important to note that bones don’t necessarily indicate the intensity or shade of skin tone within a race. Furthermore, the color of the bones themselves only reflects what the remains were exposed to since death. Racial distinctions can be detected morphologically and metrically in many places of the body, however, they are less visible.

When opposed to the straighter femora of blacks, whites have a notable anterior curve of the femur. Blacks have a narrower pelvis, which can be detected through measurements. Disparities in total body proportions are reflected in size differences. Size differentials reflect disparities in total body proportions. On average, blacks have proportionally longer limbs than whites; the reverse holds for Mongoloids. Like sexual dimorphism, the existence of racial dimorphism has led to the development of discriminant function formulae from measurements of many parts of the skeleton, but these methods are both sex and subpopulation specific. In the end, even the most experienced practitioners can be confounded by multiracial admixtures, and even the most advanced approaches cannot definitively classify them since the range of normal variation is so large that all possible variants cannot be anticipated.

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