What is the primary job of a forensic anthropologist? What are the three main things that can determined from a skeleton?

Transcription

1

2 What is the primary job of a forensic anthropologist? What are the three main things that can determined from a skeleton? What three areas of a skeleton can be used to determine sex?

3 Physical anthropologists (study of the skeleton and how it evolved) Forensic anthropologists Physical anthropologists who specialize in recovering and examining human skeletal remains where legal questions are involved (particularly a crime has been committed) Began in Used in the 1940 s to identify dead WWII soldiers. First book was written in 1939 by William Krogman

4 The first time a forensic anthropologist was called to testify in court involved a case in A Chicago murderer turned his victim s body into sausage leaving behind no body to tie him to the crime. Luckily, bone fragments were found at the factory and a physical anthropologist was able to identify them as human remains.

5 Usually, Universities and major research facilities (like the Smithsonian). They are usually consulted on a as needed basis by forensic laboratories.

6 Osteobiography (your history told by your bones) Age Sex Height Ancestry Right or left handed Behavioral information Medical conditions Childbirth Past injuries or accidents Occasionally: Time of death Cause of death

7 About 25% of the time, the remains are actually nonhuman. Can be distinguished by size, structure, or under a microscope.

8

9 Try to identify the minimum number that must be present. Duplication of bones is the easiest way Differences in age, size, structure, and preservation DNA can be used to confirm

10 Much easier once puberty has been reached. Skeletons of children often remain unsexed. Male skeletons are thicker, more robust, and bumpier because of their larger muscles. What s the best bone to use to determine sex? The Pelvis It is much wider in women to allow for childbirth The sacrum is shorter and wider in a female The coccyx is more moveable in a female Pelvic bones are lighter and smoother in a female

11

12

13

14

15

16 Differences can also be seen in the skull

17

18

19

20

21

22

23

24 Femurs can be used to indicate sex. Male femurs are larger. Female femurs join the pelvis at a sharper angle.

25 Easiest to determine on infants and children since growth rate is pretty standard. From toddler to 21 the best indicator of age is teeth Harder to determine after puberty. In adults the best indicator of age is the pelvis Bones remain constant in length as a adult until about 35 after which bone loss occurs faster than repair and bones get shorter.

26 A baby's bones begin to grow in the womb. At birth, the skeleton is partially formed. Many bones are still in "parts. The ends (epiphyses) and bony shafts (diaphyses) of long bones form separately in the womb. At birth, the ends of the long bones are mainly cartilage, with centers of bone beginning to form inside. As a child grows, the shafts get longer, and bone gradually replaces the cartilage epiphyses. Through the growing years, a layer of cartilage (the growth plate) separates each epiphyses from the bone shaft.

27 Between 17 and 25 years, normal growth stops. The development and union of separate bone parts is complete. At this point, you and your skeleton are as tall as you are going to get - with many fewer bone parts than you started with! Measuring the length of long bones can give an estimate of age for children, but this technique is useful only until bones have stopped growing.

28 The clavicle (collar bone)is the last bone to complete growth, at about age 25. The tibia completes growth at about age 16 or 17 in girls, and 18 or 19 in boys.

29 Like many other mammals, humans have two sets of teeth. "Baby" teeth (also called milk or deciduous teeth) start coming in at about 6 months, beginning with the central incisors in the mandible (lower jaw). Each tooth type (incisors, canines, premolars, molars) erupts on a predictable schedule. Permanent teeth begin to replace deciduous teeth at about 6 years and finish erupting by about 21 years of age. X-rays provide views of the unerupted permanent teeth and tooth roots still within the bone. The crown of a tooth forms first, followed by the root. Scientists estimate age by comparing the stage of tooth formation in the X-rays and bone with know dental growth standards.

30

31

32 Skeletons record an adult's age in several ways. The surfaces of the cranium, pubic bones, and rib ends hold clues. At the microscopic level, investigators can see the bone "remodeling" that takes place throughout life, as well as age-related bone breakdown.

33

34 Even after childhood growth stops, bone "remodeling" continues. Throughout a lifetime, bone makes new osteons minute tubes containing blood vessels. Microscopic exams show these changes, which can indicate adult age to within 5 to 10 years. Younger adults have fewer and larger osteons. Older adults have smaller osteons and more osteon fragments, as new ones form and disrupt older ones.

35

36 The bones that enclose the brain grow together during childhood along lines called cranial sutures. During adulthood, bone "remodeling" may gradually erase these lines, at variable rates. Closure of cranial sutures gives general information about a person's age. It is best used with additional indicators to estimate age, or when other age indicators are unavailable.

37 In children the skull is different At birth the bones are not fused together as they are for adults. They are separated by membranous areas called fontanels or soft-spots. Why is this important?

38 Wear and tear on a body throughout a lifetime affects the skeleton. Arthritis of the spine and joints can reflect increasing age. Scientists also recognize many other clues to aging, such as the appearance of the rib ends and the cartilage that joins them to the sternum. In a young adult, the rib end walls are thick and smooth, with a scalloped or rounded edge. In an older adult, the walls are thin, with sharp edges, and the rim often has bony, irregular projections.

39 Skulls bear various characteristics that provide clues about the person's ancestry/race to experienced anthropologists. Individuals with Native American ancestry have proportionately wider faces and shorter, broader cranial vaults. Individuals with European ancestry tend to have straight facial profiles and narrower faces with projecting, sharply angled nasal bones. Individuals with sub-saharan African ancestry generally show greater facial projection in the area of the mouth, wider distance between the eyes, and a wider nasal cavity.

40

41 Bones that are used a lot grow larger while bones that are seldom used become smaller. What could this tell us?

42 Pregnancy does not modify a woman's bones, with one exception. During childbirth, the pubic bones separate to allow an infant to pass through the birth canal. The ligaments connecting the pubic bones must stretch; they can tear and cause bleeding where they attach to bone. Later, bone remodeling at these sites can leave small circular or linear grooves on the inside surface of the pubic bones. These parturition pits show that a female has given birth vaginally.

43

44