Biological Anthropology Lab Report

Biological Anthropology Lab Report

Digital Lab Workbook Introduction to Biological Anthropology Laboratory Lab 7: Human Osteology Lab Objectives ● Learn major anatomical features of the human skull and postcrania. ● Calculate indices for the cranium and postcrania. ● Use anthropometric methods to estimate sex and stature. ● Understand the use of standard error in statistical measures. Lab Assignment Overview Welcome to Lab 7! You will need a computer and wifi connection to complete this assignment. You might also need a calculator; you can find a web-based scientific calculator here. This web-based consists of one major exercise and a set of assessment questions you will answer on your own time. During each exercise, you will navigate through a slide deck containing descriptive information, diagrams, images and video. Read all information in full. Use these tools, what you’ve learned in lecture, and your textbook to assist you in answering questions in the assessment portion. Below is a breakdown of the concepts covered in this workbook: EXERCISE 1 Human Skeletal Variation 1. Concept Introduction 2. The Human Skeletal System 3. Osteology & Estimation Assessment Once you’ve read through each exercise, you will complete a set of assessment questions based on the review material. You can find these questions at the end of this workbook. You will type and submit your answers into a google form where your TA will grade them. You are encouraged to review the assessment questions and prepare your answers before accessing the google form. Concept Introduction LAB 7 | EXERCISE 1 Human Skeletal Variation Bones provide a means to study the nature and degree of variation in the human body. Using clues and information from the skeletal system, practitioners in skeletal biology, osteology, and forensic anthropology study variation across an individual’s life span, between populations and even across evolutionary time. Bones are highly durable, vary between individuals in appearance (in the same way our faces and bodies do) and also they remodel several times throughout a person’s life. Additionally, because bones change in response to the environmental and biomechanical pressures placed on them, they provide a helpful model for the study of human anatomical and physiological variability. In forensic anthropological contexts, practitioners identify morphological markers in the skeleton to build a biological profile that includes traits about an individual including their age at death, sex, ancestry, stature, occupational details, pathological conditions, or traumatic injuries. This information is given to law enforcement in medico-legal situations to identify deceased or missing people. In the Exercise 1 assessment portion, you will employ osteological techniques to measure and describe human skeletal variation. 1 LAB 7 | EXERCISE 1 An Anatomical Review Human Skeletal System The human skeleton is a mechanically optimized biological system whose composition and organization reflect the functional demands placed upon it. The role of the osteologist is to identify Skull human bones from those of non-human material (i.e. animal bones) and to determine as much additional information about the bones they are confronted with. Examine the diagram on the right and the below 3D model of the human skeleton, see if you can identify the three regions specified: Pelvis, Skull, and Long Bones (Femur, Tibia, Fibula, Humerus, Radius, & Ulna). Pelvis 3D Model 3D models are a helpful tool to Femur (Long Bone example) illuminate the spatial relationships and surface structure of anatomical components. Explore and rotate a 3D model of the human skeleton below. Click Here The pelvis, skull, and (4 )long bones are a few of the most helpful parts of the body used to infer, sex, age, stature, and ancestry information. 2 Concept Introduction LAB 7 | EXERCISE 1 Osteology & Estimation A single skeleton can provide an abundance of data on an individual’s life from their age, sex, and stature all the way to past struggles like disease, accidents, and developmental instability. The most basic of inferences are estimations on the individual’s age, sex, and stature. As a person ages, their skeletal morphology will grow and change; long bones, for example, grow dramatically from childhood to adolescence as individuals grow taller. There are also subtle differences between the sexes in the morphology of some parts of the skeleton, notably the skull and pelvis. Sex Estimation Using the Skull: Sexual dimorphism constitutes the morphological differences in size and shape between males and females. The marked appearance of sexually dimorphic traits within the skull appear at puberty and progress into adulthood. We use skull traits in combination with other skeletal traits to infer the sex of a skeleton. Sex Estimation Using the Pelvis: The pelvis is a basin-shaped bone that sits between the trunk and the lower limbs. It is extremely useful in the estimation of sex because it offers the most accurate determinations. Anatomically, the male pelvis is longer, more robust, and displays more rugged features with marked muscle insertions whereas the female pelvis shows a wider sciatic notch with an obtuse angle. Stature Estimation Using the Long Bones: The stature, or individual’s height, can be inferred using measurements of an individual’s long bones, namely the humerus, femur, and tibia. When these bones are unavailable, other long bones – the ulna, radius, and fibula can also provide a range. There are several methodologies that are used within osteology to determine these estimates. 3 END OF EXERCISE 1 Take a break, then move to the assessment. Lab 7 Assessment Preview the assessment questions for Exercise 1 on the next few pages. You will type your answers to each question into a google form where your TA will grade them. You are encouraged to prepare your answers in a word document or on paper before submitting. To access the google form, use the link provided on Blackboard. Be sure you are logged in with your GW email and password. Exercise 1 Assessment Neocranium Section 1: The Cranium The human skull is composed of three regions: the neurocranium (cranial vault or braincase), basicranium (cranial base), and face. Examine this Basicranium interactive 3D Human Skull noting the definitions of each bone. Once you’ve done this, fill in each blank (below) with the name of the appropriate bone. Face View in 3D Neurocranium The _________________ are two paired bones that form the upper lateral surfaces of the skull. The _________________ forms the front of the cerebral cranium. This bone is comprised of the squama frontalis, orbital and nasal portions and sits supra-orbitally (above the orbital eye ridges). Face The _________________ are small paired bones that connect the frontal bone with the upper jaw and temporal bones. These bones intersect with the temporal bone to form an arch. The _________________ are paired bones forming the bridge of the nasal cavity. Basicranium The _________________ are paired bones that form the basal and lateral walls of the skull. These bones house the structures of the organ of hearing and vestibular system. The _________________ bone sits at the rear of the cerebral cranium and features a large hole at its base called the foramen magnum, through which the cranial cavity communicates with the vertebral canal. 4 Exercise 1 Assessment Section 2: Stature Estimation using Long Bones Using the long bones of the arm (humerus, radius, and ulna) and the long bones of the leg (femur, tibia, fibula) we can estimate an individual’s stature (~height). To do this we measure the total length of each long bone at specific locations on the bone. Examine each bone below, you’ll find a measurement table you need to estimate stature on the next page. Long Bones Arm Bones Humerus Radius 1 Leg Bones Ulna 2 Tibia Fibula Femur 3 4 5 6 5 Exercise 1 Assessment Section 2: Stature Estimation using Long Bones Measurement Type Description Measurement (cm) 1 Maximum length of the humerus: Measure from the distal to proximal end. 34.5 2 Maximum length of the radius: Measure from the distal to proximal end. 23.8 3 Maximum length of the ulna: Measure from the distal to proximal end. 25.1 4 Maximum length of the tibia: Measure diagonally from the lateral condyle to the medial malleolus. 34.5 5 Maximum length of the fibula: Measure from the distal to proximal end. 35.1 6 Bicondylar length of the femur: Set both condyles firmly against the stationary upright. Note that a condyle is a round protuberance at the end of a bone that often forms a joint. 34.7 Question 1: Using the long bone measurements provided in the table above (in red), calculate the three most common cranial indices. Brachial index (radius length / humerus length) × 100 = ? Crural index (tibia length / bicondylar femur length) × 100 = ? Intermembral index (humerus length+radius length / bicondylar femur length+tibia length)× 100 = ? 6 Exercise 1 Assessment Section 2: Stature Estimation using Long Bones Question 2: Assuming these bones belong to the same Stature formulae for Females SE individual and assuming this individual was female, use the 3.08 × Humerus Length + 64.67 4.25 2.75 × Radius Length + 94.51 5.05 3.31 × Ulnar Length + 75.38 4.83 2.28 × Femur Length + 59.76 3.41 2.45 × Tibia Length + 72.65 3.70 2.49 × Fibular Length + 70.90 3.80 stature formulae in the table to the right to estimate her stature during life. Calculate stature for the humerus and femur only. All formulae are followed by their standard error (SE) in red; this indicates how much variation is in the estimate. The lower the SE, the better the estimate. These formulae report results in centimeters. Stature estimate for humerus (cm) = ? Stature estimate for femur (cm) = ? Question 3: Let’s say the stature estimates you calculated for the humerus differed from those you calculated for the femur. What would this suggest? 7 Exercise 1 Assessment Section 3: Qualitative Sex Estimation In primates, males are usually larger than females. Modern humans also exhibit a degree of sexual dimorphism, described as differences in shape or size due to sex. In humans, sexually dimorphic traits vary within and between populations. It is common in our culture to refer to sex and gender interchangeably, but sex here refers to biological traits and gender refers to the behavioral, cultural, and psychological traits we associate with a sex. The best skeletal areas for estimating sex are the skull and the pelvis. High quality diagrams and images of skull and pelvic anatomy are included in the back of this digital workbook. Review each image and come back to answer the below questions. Question 1: Why do you think these two areas are the best to use for sex determination? Question 2: Which skeletal element (skull or pelvis) do you think provides higher accuracy in determining sex? Question 3: Examine the two 3-dimensional mystery skulls linked below. Based on your review of the images and qualitative skull traits, decide which skull is female and which is male (multiple choice-matching question). View Mystery Skulls Question 4: Describe 2 traits you used to determine the sex of the two mystery skulls. Question 5: Examine the two 3-dimensional mystery pelvi (singular pelvis) below. Based on your review of the images and qualitative pelvic traits, decide which pelvis is female and which is male (multiple choice-matching question). View Mystery Pelvi Question 6: Describe 2 traits you used to determine the sex of the two mystery pelvi. 8 Exercise 1 Assessment Section 4: Metric Sex Estimation Both quantitative and qualitative data can be useful for evaluating scientific phenomena. In Section 3, the characteristics we used to describe male and female skulls and pelvi are qualitative. If we had measured the bones and provided numerical values, these data would be quantitative. We could have measured the same sex traits we described in Station 5 to yield quantitative data. We will perform a quantitative analysis of one feature on a pelvis – the width of the greater sciatic notch. Recall from the Section 3 images that the greater sciatic notch is usually wider in modern human females and more narrow in males. Here we will use actual measurements of this notch to make a sex determination. In a normal lab setting, you and other members of your lab group would take a set of repeated measurements. Below, a sample set of measurements has been provided for you in red. Using these measurements, determine the mean for your sample. Trial 1 Measurement (cm): 8.1 Trial 2 Measurement (cm): 8.3 Trial 3 Measurement (cm): 8.1 Trial 4 Measurement (cm): 8.2 Question 1: Mean = ? Greater Sciatic Notch 9 Exercise 1 Assessment Section 4: Metric Sex Estimation Because error can occur in measurements, particularly when they are taken by different observers, it is sometimes helpful to report the standard error of a measurement. Standard error (SE) indicates how much variation is in the estimate. To calculate the standard error of this set of pelvic measurements, use the following formula: Standard Error of the Mean (SEM) = √S²/N First, plug in the information you have, then use the SEM formula! Variance = s2 → (SS) / (V) ? SS = Sum of Squares → (X1 − Z) 2 + (X2 − Z) 2 + (X3 − Z) 2 + (X4 − Z) 2 ? Z = Mean ? V = degrees of freedom → N − 1 ? N = the number of observations ? Xsubscript = The trial number ? Question 2: What is your SEM _________? Question 3: A “good” standard error depends on the questions you are asking and the data you use. For our purposes, your SEM should be less than 10% of your mean measurement (Z) for the greater sciatic notch. Would your SEM be considered “good” for our experiment? 10 Skull Traits If it seems like the variation here is slight… IT IS! The morphological differences between males and females within and across populations are highly variable and often minute. Frontal Bone Upper Eye Margin Eye Orbits What other differences can you identify? Check out additional images on the following pages. Jawline Chin Typical Female Typical Male Smaller and lighter or more gracile skull Larger, heavier or more robust skull Rounded frontal bone when viewed in profile (forehead) Sloping less rounded forehead in profile (frontal bone) Smooth supraorbital ridge (brow) Raised/ prominent supraorbital ridge (brow) Round eye orbits Eye orbits that are more square in shape Sharp upper eye margins Blunt upper eye margins Pointed chin Square chin Sloping (obtuse) angle of the jaw Vertical (acute) angle of the jaw 11 Supraorbital Ridge Mastoid Process Jawline Chin Typical Female Typical Male Smaller and lighter or more gracile skull Larger, heavier or more robust skull Rounded frontal bone when viewed in profile (forehead) Sloping less rounded forehead in profile (frontal bone) Smooth supraorbital ridge (brow) Raised/ prominent supraorbital ridge (brow) Round eye orbits Eye orbits that are more square in shape Sharp upper eye margins Blunt upper eye margins Pointed chin Square chin Sloping (obtuse) angle of the jaw Vertical (acute) angle of the jaw 12 Female Male Female 13 Female Male Female 14 Female Male Female 15 Female Male Female 16 Female Male Female 17 Female Male Female 18 Female Male Female 19 Female Male Female 20 Iliac Blade Sacrum Pelvic Inlet Pelvic Traits Typical Female Typical Male Wider, shorter sacrum with less curvature Longer more curved sacrum Larger sub pubic angle Smaller sub pubic angle Wider, flared iliac blades More narrow, vertically pointed iliac blades Larger, more oval shaped pelvic inlet Smaller, more heart-shaped pelvic inlet Triangular shaped obturator foramen Oval shaped obturator foramen Greater sciatic notch opening is wider in profile Greater sciatic notch opening is more closed in profile Smaller acetabulum that faces anteriorly Larger acetabulum that faces laterally 21 Iliac Blade Sacrum Sub Pubic Angle Typical Female Typical Male Wider, shorter sacrum with less curvature Longer more curved sacrum Larger sub pubic angle Smaller sub pubic angle Wider, flared iliac blades More narrow, vertically pointed iliac blades Larger, more oval shaped pelvic inlet Smaller, more heart-shaped pelvic inlet Triangular shaped obturator foramen Oval shaped obturator foramen Greater sciatic notch opening is wider in profile Greater sciatic notch opening is more closed in profile Smaller acetabulum that faces anteriorly Larger acetabulum that faces laterally 22 Greater Sciatic Notch Acetabulum Typical Female Typical Male Wider, shorter sacrum with less curvature Longer more curved sacrum Larger sub pubic angle Smaller sub pubic angle Wider, flared iliac blades More narrow, vertically pointed iliac blades Larger, more oval shaped pelvic inlet Smaller, more heart-shaped pelvic inlet Triangular shaped obturator foramen Oval shaped obturator foramen Greater sciatic notch opening is wider in profile Greater sciatic notch opening is more closed in profile Smaller acetabulum that faces anteriorly Larger acetabulum that faces laterally 23 Female Male Female 24 Female Male Female 25 Female Male Female 26 Female Male Female 27 Female Male Female 28 Female Male Female 29 Female Male Female 30 Female Male Female 31 END OF LAB 7 Submit your assessment questions and you’re all set!





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