SEX DETERMINATION FROM HUMAN SKELETAL REMAINS {SKULL , PELVIS , STERNUM}

As humans, we have three basic social groups. These groups are Caucasoid, Mongoloid, and Negroid. With the addition of inter-breeding, many other subgroups can be found. Each group possesses unique skeletal characteristics which allow us to "race" the remains of person. In addition to race, we can also estimate age, stature, and sex.

It consists of a five phase procedure:

1) A general description and confirmation of the human origins of the material.

2) The estimation and segregation of the minimum number of individuals.

3) The determination of sex.

4) The estimation of age.

5) The estimation of stature.

Using Bones for Identification

The human skeleton consists of both fused and individual bone. Fused bones include those of the pelvis and the cranium.At birth a newborn baby has approximately 300 bones, whereas on average an adult human has 206 bones . The difference comes from a number of small bones that fuse together during growth, such as the sacrum and coccyx of the vertebral column.

IntroductionSkeleton is an excellent material in living and non-living population for genetic, anthropological, odontologic and forensic investigations. Skull and bone features vary from male to female and differentiation is usually based on the male features that are typically more pronounced and marked than female features.

Krongman ranks accuracy of sex determination using the pelvis at 95% , the skull at 90%, the pelvis and skull at 98% and long bones at 80%.

The determination of sex by examination of the skeleton is based upon the appearances of:1. Pelvis (innominates + sacrum )2. Skull (cranium + mandible )3. Long bones (Humerus , Femur )4. Sternum5. Scapula , metacarpal bones

SEXUAL DIMORPHISMDifferences between men and women include all the features related to reproductive role, notably the endocrine (hormonal) systems and their physical, psychological and behavioral effects.

SEXUAL DIMORPHISM – BASIC PRINCIPLES

The evaluation of sexual dimorphism in skeleton is generally based on two factors:1. Size difference2. Function related differences.

Determination of sex is based on two methodological approaches:

1.Morphological (based on Shape ) Adult males and females differ in both general size and shape, and this variation is reflected in the skeletal anatomy.

2. Osteometric (based on bone dimensions) Males longer or larger than females.

The skull is a bony structure which serves as the general framework for the head. The skull supports the structures of the face and protects the head against injury.The skull can be subdivided into two parts: the cranium and the mandible.

SKULLThe features that indicate sex are :1.General appearance2.Supra orbital ridges3.Orbits4.Glabella5.Zygomatic arches6.Mastoid processes7.External occipital protuberance8.Mandible9.Palate

MALE FEMALE

When compared, the female skull appears smaller and more gracile. The male skull is usually larger and more rugged.

This is the region directly above the orbit and nose, or the "brow ridge“.Less pronounced=femaleMore pronounced=male

Supraorbital ridges

ROUNDISH WITH SHARP MARGINS

MALE FEMALE

SQUARISH WITH ROUNDISH MARGINS

ORBITS

The frontal bone (forehead) of males tends to be slanted back and on females it tends to be more rounded

GLABELLA

WELL DEVELOPED ILL DEVELOPED

MALE FEMALE

Zygomatic arches

In females, the zygomatic arch is less pronounced, and tends to not extend posteriorly beyond the external auditory meatus.

In males, the zygomatic arch is more pronounced or robust, and tends to extend posteriorly beyond the external auditory meatus.

MASTOID PROCESSESThe mastoid processes are located on the inferior portion of the temporal bone, just posterior to the external auditory meatus.

EXTERNAL OCCIPITAL PROTUBERANCE

MALE FEMALE

The mandible together with the maxilla, the largest and strongest bone of the face . It forms the lower jaw and holds the lower teeth in place.

The male mandible tends to have a “square” shape.

Mandible of female tends to have a pointed chin.

Chin (anterior mandible)

Mandible in the male is closer to a right angle than the female. In the female, the ramus is an obtuse angle to the lower jaw bone, i.e., greater than 90 degrees. The ramus in the male is wider and larger.

RAMUS (rear of the mandible)

MALE FEMALE

LARGER,WIDER AND BROADER

SMALLER AND NARROWER

PALATE

MALE FEMALE

The pelvis comprises the two innominates and the sacrum.

PELVIS

The hip bone (or innominate bone) is a large, flattened, irregularly shaped bone.Together with the sacrum and coccyx, it comprises the pelvis.ComponentsIt consists of three parts, the ilium, ischium, and pubis, which are distinct from each other in the young subject, but are fused in the adult.

The best indicator of sex on the adult skeleton is the shape of the pubic bone of the pelvis.

HIP BONE

Sex Determination from Pelvic Morphology

The pelvic girdle is the most sexually dimorphic region of the skeleton, and it can be used to determine sex with a high degree of accuracy. The sexual dimorphism of the pelvis is primarily the result of reproductive mechanics, and is not readily apparent until adolescence.

Sex differentiation in the human pelvis

1. Overall appearance between the two pelvic regions .The male pelvis is larger and more robust than the female pelvis. 2. The size of the opening between the hips (A). The female skeleton requires this additional room for birthing. 3. The hips in the male (B) are more vertical than the female's.4.At the rear of the pelvis is the coccyx (C), the male coccyx is larger than the female's. 5.The angle at the front of hips (D), where both sides join (pubic symphysis) is an obtuse angle in the female, and closer to 90 degrees in the male. The female obtuse angle is in-line with the broader birthing canal.

Five features in innominate that indicate sex in pubic region are:

(1) width of sciatic notch (inferior ilium)

(2) subpubic angle (concavity)

(3) ventral arc (on the pubis, near the symphysis, ventral)(4) ischio-pubic ramus (bone connecting pubis and ischium)

PELVIS

(5) acetabulum diameter (lateral innominate)

MALE FEMALE

SMALL AND DEEP WIDER AND SHALLOWER

SCIATIC NOTCH

SCIATIC NOTCH

Generally, the sciatic notch tends to be wider in the female and narrower in the male.

The subpubic angle is much wider in females than in males, typically more that 90 degrees and less than 90

degrees, respectively.

LESS AND “V” SHAPED WIDE AND TEND TO “U” SHAPEDSUB-

PUBIC ANGLE

MALE FEMALE

It is the curved ridge of bone on anterior surface of the pubic bone.It is common in females and almost never seen in males.

The space in the middle of the pelvic bone (the pelvic inlet) is larger in women to facilitate birthing.

The pelvic inlet is the space you see when both innominates and sacrum are articulated.

PELVIC INLET

The sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity.

The sacrum articulates with four bones:•the last lumbar vertebra above •the coccyx below •the hip bone on either side

Sexual dimorphismThe sacrum is noticeably sexually dimorphic .In the female the sacrum is shorter and wider than in the male.The bone is also directed more obliquely backward; this increases the size of the pelvic cavity.Straighter in males & curved in females.

MALE FEMALE

The sternum is an elongated, flattened bone, forming the middle portion of the anterior wall of the thorax. Its upper end supports the clavicles and its margins articulate with the cartilages of the first seven pairs of ribs. It consists of three parts, from above downward:•Manubrium •Body of sternum •Xiphoid process

<125 mm = female>155 mm = maleThese figures are from Bass

• The Essentials of Forensic Medicine By : Cyril John Polson , D.J.Gee , Bernard Knight

• Encyclopedia of Forensic Sciences

• Clinical Anatomy for Medical Students By : Richard S . Snell

• Wikipedia

• Personal Identification from skeleton or its remains By : G.S. Kaler & N.A. Butt