Determination of Sex. Tips to keep in mind. Sex Differences in Os Coxae

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Elfrieda Jenkins
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1 Dead Men DO Tell Tales: An Introduction to Determining Age and Sex of the Human Skeleton Based on a lecture by Valerie Dean O Loughlin, Ph.D. Assistant Professor of Anatomy Indiana University Presented at HAPS 2002 Determination of Sex Male and female human skeletons differ both in general shape and size. However, patterns of sexual dimorphism can vary among groups. For example, male Asian skeletal remains can be less robust than female Native American skeletal remains. Thus, one cannot use size as the only factor to determine sex. The most reliable indicator of sex is the os coxae (hip bones), followed by the skull. Tips to keep in mind Multiple features on each bone can be used to determine sex. It is common for some of these features to appear more male and others female if this happens, sex is determined by the greatest number of features. For example, if the skull demonstrates 4 male-like traits, and 7 female-like traits, then you would classify the skull as females. It is difficult to impossible to determine the sex of infant and juvenile remains. Most infant/juvenile remains appear female-like until well after puberty. Sex determination should be made with respect to the general size/robusticity patterns of the population from which the skeletal remains came. Like reading an EKG, determining sex of a skeleton is an art. It takes great practice to precisely determine sex. Sex Differences in Os Coxae Os Coxae Feature Male Characteristic Female Characteristic Superior Inlet Heart shaped Spacious, wide and oval General Size More robust and muscle-marked Less robust Obturator Foramen Larger and oval Smaller and triangular Acetabulum Larger, directed more forward/ Smaller, directed more Anteriorly Laterally Greater Sciatic Notch Narrow and deep Wide and shallow Body of Pubis Short, triangular Longer, more rectangular Subpubic Angle (area underneath the two pubic bones) Preauricular Sulcus (depression between greater sciatic notch and sacroiliac articulation) Narrow, V-shaped Usually absent Broader, more convex Usually present 1

2 Aging by Pubic Symphysis The surface of the pubic symphysis undergoes changes as we age. It has proven to be a good, reliable indicator of age. Typically, the young adult pubic symphysis appears billowed and rugged, but by age 35 it becomes more worn and develops a rim. After age 35, the surface further erodes and degenerates. 2

3 Sex Differences in the Skull Skull Feature Male Characteristic Female Characteristic General size More robust More gracile/delicate Nuchal Crest (prominence on back of skull, in occipital region) Mastoid Process Supra-orbital margin (upper orbit rim) Supra-orbital ridge ( brow ridges ) Mental Eminence (chin) Gonial Angle (side of jaw angle) Well-demarcated nuchal lines and a prominent bump or hook Large, projects below the external auditory canal Thick, rounded, blunt border Prominent Squarish, greater forward projection Flared, Less obtuse, <125 degrees (typically, about 90 degrees) External surface of occipital bone is smooth, with no bony projections here Smaller Thin, sharp border Little or no prominence More pointed (versus squarish), little forward projection Typically > 125 degrees 3

4 Determination of Age There are many methods to determine the age at death of a skeleton. Some of these methods work best for juvenile/immature remains, whereas others may work best for adult skeletal remains. Classes commonly used for skeletal remains: 1) fetal (before birth), 2) infant (birth 3 yrs), 3) child (4-12 yrs), 4) adolescent (13-19 yrs), 5) young adult (20-34 yrs), 6) middle adult (35-49 yrs), 7) old adult (50+ yrs) Aging by the Skull After the os coxae, the skull (cranium plus mandible) is the next most reliable structure from which to determine the sex. The skull exhibits a varying degree of sexual dimorphism. However, this dimorphism can vary from population to population. Thus, one should realize that sex determination from the skull is dependent upon the population. Aging by Cranial Suture Closure Cranial sutures fuse progressively as one ages. Typically, the anteriorly-placed sutures (coronal) fuse first, followed by the more posteriorly-placed sutures (i.e., sagittal and lambdoidal, respectively). However, there is considerable variability in closure rates, so this aging method should be used in conjunction with another methods. One cranial feature that has a high reliability rate is the spheno-occipital synchondrosis (at the base of the skull), which fuses between 20 and 25 years for over 95% of populations studied. 4

5 The figure below shows the 10 areas where sutures should be examined. Each suture should be graded with the following scale: 0=open suture, 1=minimal closure, 2=significant closure of suture, 3=completely obliterated suture. The numbers should be added together and a raw score is given, which with the two tables, could be used to estimate age. Other Age Determination Methods Subadult/Juvenile remains can be aged with the following methods: Dental eruption Epiphyseal union Dental attrition (wear) sometimes Composite score Mean Age Standard Deviation (yrs) Adult remains can be aged with the following methods: Dental attrition (wear) Cranial suture closure Pubic symphysis changes Aging by Dental Eruption Aging by Epiphysial Fusion 5

6 Determination of Stature There is a correlation between long bone length and stature. This correlation varies among populations; even between males and females. Researchers have used skeletal remains from modern populations to develop formulas to estimate stature. Formulas are both sex and population dependent. It is unclear what error is introduced when these formulas are used with archaeological specimens The following table lists formulas for three populations. All measurements of the bones should be maximum length measurements. These bone measurements preferably should be taken with an osteometric board. Of the bones listed, the femur typically provides the most accurate stature estimation. Paleopathology The study of diseases in ancient populations, as revealed by skeletal remains. While many pathologies can be detected in the skeleton, these cases typically represent the more severe forms of pathologies. For example, only the more severe cases of tuberculosis will leave evidence of such on the skeleton. Thus, when examining evidence of pathology in skeletal remains, one must realize that some less serious forms will not be detected. 6

7 Paleopathology What are some pathologies/anomalies that can be detected in the skeleton? Trauma (recent or healed fractures, dislocations, subluxations) Some infectious diseases, like tuberculosis, osteomyelitis (infection/inflammation of the bone), leprosy, syphilis, other infections Metabolic/nutritional disorders, like scurvy, rickets, osteoporosis, osteomalacia Blood (hemopoietic) disorders, such as anemias, leukemias (sometimes), myelomas Endocrine disorders, such as pituitary gigantism, dwarfism Benign and malignant tumors Arthritis (osteoarthritis, gout, rheumatoid arthritis, ankylosing spondylitis which causes the characteristic bamboo spine ) Caries (cavities) and other dental pathologies Skeletal dysplasias, such as achondroplasia (dwarfism), osteogenesis imperfecta (characterized by numerous fractures) Scoliosis (lateral curvature of spine), kyphosis (increased anterior curvature in thoracic spine) 7

FORENSIC ANTHROPOLOGY NOTES

FORENSIC ANTHROPOLOGY NOTES Forensic Anthropology = the examinations of human skeletal remains for law enforcement agencies to determine the identity of unidentified bones. Questions asked: 1. Are the