Analysis of Skeletal Remains - Worksheet Return to The Crime Lab See also the Analysis of Skeletal Remains Lab, which involves the use of bone models, as well as actual bones. In this activity, skeletons will be examined for how they vary according to the following: Gender Race Age Height (based on the pelvis & skull) (based on the maxilla, and other characteristics of the skull) (based on general characteristics) (calculated based on the length of individual bones) Students will be evaluated as to whether or not they correctly identified the gender, age, and race of the individual. Being able to determine Left and Right is also crucial to the practice of forensic anthropology, not only for skeletal reconstruction, but also to determine the number of casualties. Reference to a complete skeleton is helpful, but one is never around when you need one (as would happen if you are investigating a skeleton in the woods. That will not be a part of this activity, but it easily could be. GENDER One of the issues of concern to the forensic anthropologist is the gender of the human remains. There are several things than may, on the surface, be useful to gender determination, but, on upon closer examination, are not very useful. For example, females are, on average, shorter than males, but a short skeleton can easily be male. This is due very simply to the fact that each gender follows a Gaussian distribution (a.k.a. a Bell Curve). When one graphs the data (as a histogram, or calculated to a bell curve), there is clearly gender overlap. Histogram, the formula to calculate a bell curve, and the bell curve images are from http://www.usablestats.com/lessons/normal As such, it is easily possible to have a female at the tall end of the height curve, and a male at the short end of the height curve. The curves for gender overlap, for the most part, with the peak of each curve slightly off-set. It is easy to say that the average height is shorter for females than it is for males, but that information is useless when we examine two individual skeletons. There are several ways to more accurately determine the gender of a skeleton. One of them is by examining the pelvis, which can be identified accurately 95% of the time. Images from http://www.clipart.com/, and adapted by Mr. Lazaroff Original images from http://www.boneclones.com/ Circle or highlight the Appropriate Answer Angle > 90 degrees or < 90 degrees Angle > 90 degrees or < 90 degrees Sacrum Forward or Backward Sacrum Forward or Backward Pelvic Outlet Small or Large Pelvic Outlet Small or Large Ilia Close or Spread Ilia Close or Spread Female or Male Female or Male Another way is to examine the skull. This is still fairly accurate, but not as accurate as the pelvis. Forensic anthropologists can accurately identify the skull somewhere between 85 and 90% of the times. This can be complicated by several factors. If a skull is incomplete, then, of course, there is less to work from. Some of the distinguishing characteristics, such as larger bone landmarks for muscle attachments in males, can be easily confused with the landmarks of more athletic females. To put it simply, since the landmarks are often for the attachment of muscles, the larger the muscles, or the more one uses the muscles, the larger the landmarks. Landmarks Female Male Chin Mastoid Process Rounded Square Small Large Small Large (Not Prominent) (Prominent) General Anatomy Gracile (i.e., Graceful) Forehead Vertical Robust Receding (Behind Ear) External Occipital Protuberance (Back of Skull) Brow Ridges (Location of Eyebrows) Muscle Lines Orbital Margins (Edge of Eye Socket) Angle of Ascending Ramus (Back Corner of the Jaw) (Careful with the comments . . .) Slightly Developed Prominent Slightly Developed Prominent Sharp Rounded Obtuse Close to 90 degrees Now try to identify the skulls below by gender: Original images from http://www.boneclones.com/ Circle or highlight the Appropriate Answer Chin Rounded or Square Chin Rounded or Square Mastoid Process Small or Large Mastoid Process Small or Large Occipital Protuberance Small or Large Occipital Protuberance Small or Large General Anatomy Gracile or Robust General Anatomy Gracile or Robust Forehead Vertical or Receding Forehead Vertical or Receding Brow Ridges Slight or Prominent Brow Ridges Slight or Prominent Muscle Lines Slight or Prominent Muscle Lines Slight or Prominent Orbital Margins Sharp or Rounded Orbital Margins Sharp or Rounded Angle of Ramus 90 degrees or Obtuse Angle of Ramus 90 degrees or Obtuse Gender Female or Male Gender Female or Male Now that you have had some practice, what about this lone skull? Circle or highlight the Appropriate Answer Chin Rounded or Square Mastoid Process Small or Large Occipital Protuberance Small or Large General Anatomy Gracile or Robust Forehead Vertical or Receding Brow Ridges Slight or Prominent Muscle Lines Slight or Prominent Orbital Margins Sharp or Rounded Angle of Ramus 90 degrees or Obtuse Gender Female or Male Original image from http://www.boneclones.com/ For more information on "sexing" the skeleton, see the following page: http://www.uic.edu/classes/osci/osci590/7_07Notes%20for%20Week%207.htm In addition to determining gender, there are characteristics of the skull that can be used to determine the race of an individual. Many of these features are quite subtle, and require detailed examination of the skull. A couple of features, however, are more easily seen. For example, in people of African ancestry, the nasal opening is more flared. Another example is that of the zygomatic arch (or cheek bone), which is angled more forward in people of Asian ancestry, thus giving the person a slightly more flattened face.. Unfortunately, a true examination of racial characteristics is not possible on a worksheet. Original images from http://www.boneclones.com/ African Male Nose Asian Male Cheek (Note Flaring) (Note how it is angled forward) Now Compare Examples of Skulls from these three Races Asian African European AGE The idea of age being represented by the skeleton was introduced in the Skeletons as Forensic Evidence website we looked at earlier. One way we could tell was by looking at the condition of the bones themselves, with the older bones being more likely to be arthritic. Examine the bones below, and label which is arthritic (and therefore older), and which is the younger: Original image from http://www.boneclones.com/ Circle or highlight the Appropriate Answer Arthritic Yes or No Arthritic Yes or No Younger or Older Younger or Older Another way to determine age is by looking at the development of the sutures: Images from http://www.clipart.com/, and adapted by Mr. Lazaroff Note, for example, that the adult skull has no remaining suture (called the frontal suture) in the middle of the Frontal bone. Remember, also, that all the sutures ultimately become more filled-in ("closed") as we age. Compare the two skulls below to determine which skull is from an adult, and which is from an adolescent: Original images from http://www.boneclones.com/ Circle or highlight the Appropriate Answer Frontal Suture Present or Absent Frontal Suture Present or Absent Other Sutures "Open" or "Closed" Other Sutures "Open" or "Closed" Adolescent or Adult Adolescent or Adult Can you see the fontanels in the image below? Note how many places in the infant skeleton are still made of cartilage, which appears blue. The indicates how much of the skeleton is still developing. Please note that the pelvis is still divided into the three parts: ilium, ischium, and pubis; these will ultimately fuse into a single pelvic bone (a.k.a., Os coxa, or Innominate). Note the many bones in the sternum, which will ultimately fuse into one. Remember that the total number of bones in the skeleton, 206, is based on an adult skeleton. The actual number in an infant is much higher! Please also note that there is a great deal of cartilage at the end of each of the long bones, an area called the epiphysis (see the image below). (If each end is called the epiphysis, how do we show one end of the humerus from the other end in the name? Easy: Proximal epiphysis& Distal epiphysis!) The cartilage at all the epiphyses (pl.) indicates that a great deal of growth in long bones is actually happening at the ends (thus making the bones longer. Another way to determine age is to look at the epiphysis (end) of a long bone (the shape of which should be self-explanatory). First of all, an x-ray is actually a film negative. When light (Don't forget that x-rays are a form of light!) hits photographic film, it turns the film black; in making a print (i.e., making a negative of the negative, which is therefore a positive), the image printed will look white. The more light, the darker the negative, and the brighter the developed image. X-rays pass easily through muscle and most organs, butnot through bone; this will make the bones appear lighter in the negative (which works well for us, as bones are already white!). An x-ray image (radiograph) of a child will reveal a dark area where the growth plates are still made of cartilage (more x-rays can pass through cartilage, which is less dense, thus making a dark area); these areas are the epiphyseal plates. An x-ray radiograph of an adult will reveal a white area where the growth plates have been turned into bone (fewer x-rays can pass through bone, which is more dense, thus making a white line); these areas are the epiphyseal lines. Examine the radiographs below, and determine whether they are from adults or children: Images are from http://www.dartmouth.edu/~anatomy/knee/radiographs/radio3.html Circle or highlight the Appropriate Answer Epiphyseal Plate or Line Epiphyseal Plate or Line Adult or Child Adult or Child HEIGHT Lastly, often a skeleton is incomplete. Despite this, it is still possible to calculate, with a certain amount of accuracy, the height of a skeleton, even if the calculation is based upon a single bone! Apart from height, average weight can be calculated based on not only the general size of the bones, but also by evidence of the weight borne by the bones. These weight calculations, however, are too complex to demonstrate without detailed examination of the bones, which obviously cannot be done on a paper worksheet. Any of the major bones of the arm or leg can be used to determine height. The major bones of the arm are the humerus, ulna, and radius. The major bones of the leg are the femur, tibia, and fibula. The Given that not everyone's arm to leg ratio is exact, height is usually estimated by using more than one bone, if possible. Granted, a complete skeleton does not require calculation, but skeletons are not always complete, especially ancient skeletons. The calculations we will be looking at will be of the femur, humerus, and radius. SmartDraw Image adapted by Mr. Lazaroff In order to calculate the height, in inches, follow the formulas below for each of the bones. Be sure to indicate height not only in the total number of inches, but in terms of feet and inches (i.e., a person who is 62 inches is also described as being 5 feet, 2 inches tall, or 5' 2"). NOTE: The calculations, of course, are different when measurements are in centimeters. Bone (See Image) Formula for calculating Body Height (in inches), but only if you use the, "uh, 'merican" system! Female Male Femur Height equals (length of femur x 1.94) + 28.7 Height equals (length of femur x 1.88) + 32 Humerus Height equals (length of humerus x 2.8) + 28.1 Height equals (length of humerus x 2.9) + 27.8 Height equals (length of radius x 3.3) + 34 Radius Height equals (length of radius x 3.3) + 32 In order to calculate the height, in cm, as most of the world does, follow the slightly different formulas below for each of the bones. Formula for calculating Body Height (in cm) . . . The System EVERYONE ELSE Uses! (See Image) Female Male Femur Height equals (length of femur x 1.94) + 72.9 Height equals (length of femur x 1.88) + 81.3 Humerus Height equals (length of humerus x 2.8) + 71.4 Height equals (length of humerus x 2.9) + 70.6 Radius Height equals (length of radius x 3.3) + 81.3 Height equals (length of radius x 3.3) + 86.4 Bone Now plug in the following numbers into the formula to determine the height to the nearest 1/2 inch (expressed both as inches -- x" -- and as feet and inches -- x' + y") of the deceased: Gender Bone Length Female Femur Male Femur Calculations SHOW YOUR WORK! Height x" in Inches Height Multiply by x' + y" 2.54 to get (Feet + the Height Inches) in cm 17.9" 17.9" NOTE: The same length is shown to illustrate the different calculations required for the same measurements, depending on the gender of the deceased. Female Humerus 11.5" Male Humerus 11.5" Female Radius Male Radius 9.3" 9.3" Check Your Work using our Bone Length to Body Height Calculator Gender Bone Length Calculations SHOW YOUR WORK! Height in cm Multiply by 0.3937 Height in to get the Feet & Height Inches in inches Female Femur 45.5 cm Male Femur 45.5 cm NOTE: The same length is shown to illustrate the different calculations required for the same measurements, depending on the gender of the deceased. Female Humerus 29.2 cm Male Humerus 29.2 cm Female Radius 23.6 cm Male Radius 23.6 cm QUESTIONS: 1. What is the easiest way to determine the gender (using the skeleton) of an individual, and why? 2. What is the easiest way to tell (using the skeleton) whether a teenager is lying about her/his age, and why? 3. Why can determining gender from a skull be difficult? 4. Why should a forensic anthropologist use more than one bone (if possible) to determine the height of an individual? 5. What other issue is important to question four, especially if there is only one bone from which to work?