THE HUMAN SKELETON Can reveal basic information about the individual and about the population The first two things you want to know about any individual skeleton are AGE and SEX Sexing a skeleton Depends on sexual dimorphism Not possible until secondary sexual characteristics develop or until after puberty Sexing a skeleton FEMALES MALES Generally are more gracile Generally are more smaller less heavily robust larger more muscled heavily muscled The more muscle the denser the bone and more prominent muscle attachments female Two adult mandibles from same Eskimo site Greenland Canada Whitehead et al 2005 255 male Male more robust Female more gracile brow ridge supraorbital ridge Skull 2nd best area to use to determine sex of skeleton France 1998 90 Female Male nuchal crest chin mastoid process Brow ridges more prominent in males Chin is more square in males Female skull smaller smoother and more gracile Nuchal crest a muscle attachment point larger on males Mastoid processes larger in males chin square nuchal crest larger in male mastoid process larger in male Bass 1987 82 Pelvis best area for determining sex sciatic notch Male pubis Female ilium France 1998 90 Male Female Male pelvis narrower female is broader in female ilia flare out more resulting in Female have longer pubic portion and subpubic angle is greater Sciatic notch wide in female narrow in male Aging a skeleton Can get a pretty good age for young but from about 25 30 years onward estimation of age depends almost entirely on degenerative changes 1 Tooth eruption 2 Epiphyseal closure 3 Skull suture closure 4 Pubic symphasis roughness Age Estimation tooth eruption Steele Bramblett 1988 103 Cross section of 6 year old child s mandible showing developing but unerupted permanent teeth Humans have deciduous and permanent teeth that tend to erupt at known ages Deciduous teeth 20 of them erupt between 7 24 months of age 2 6 years the roots ossify Permanent teeth erupt between 6 18 years of age the third molar may never erupt or erupt late Tooth wear is NOT reliable for aging depends on diet use of teeth as tools Whitehead et al 2005 257 Age estimation epiphyseal closure A child has 300 bones yet an adult has only 206 Long bones grow in three sections diaphysis shaft plural diaphyses epiphyses two ends singular epiphysis When growth is complete the cartilaginous disks ossify We know when this happens when the epiphyses unite with the diaphysis because the cartilaginous disks ossified Age estimation epiphyseal closure Ossification centers in a subadult femur epiphysis Adult femur Newborn epiphysis diaphysis bone shaft An adult human has 206 bones During the first 16 18 years of life we more than triple in length epiphysis This growth takes place between the epiphysis end of bone and the diaphysis shaft of bone When the epiphysis unites with the diaphysis growth stops diaphysis Premature union results in dwarfism Failure of union results in gigantism Growth plate 16 23 15 22 23 28 12 16 13 18 19 25 17 20 18 23 14 18 18 25 14 18 14 19 16 20 17 22 France 1998 96 Years for epiphyseal union Skull Sutures Human babies are born with 300 bones Infant s head has fontanelles Fontanelles fill in with bone Where bone meets form sutures Age estimation skull suture closure Just as long bones grow so does the skull The plates eventually join together and with age the sutures between the plates smooth out But skull suture closure is not considered very reliable From the outside of the skull if all sutures are completely open the individual is less than 84 years of age If all sutures are completely closed the individual is 36 or older Age estimation pubic symphysis This is where the two pelvic bones join in the front Ten age phases of changes established based on how rugged or smooth the surface is Male younger older SUMMARY First two things you want to know about a skeleton SEX Pelvis female wide male narrow Skull male bigger brow ridge muscle attachments more square chin Males generally more robust females gracile AGE Dental eruption teeth erupt at known ages Epiphyseal closure diaphyses epiphyses unite Pubic symphysis change in roughness Cranial suture closure least exact What else can we learn from a skeleton Stature Injuries that affect bones Cause of death maybe Diseases maybe General health and nutrition Diet Cultural practices Genetic relationship Reconstruct face maybe What else can we learn from a skeleton Stature height from length of long bones Injuries and whether you lived to heal or not Whitehead et al 2005 246 Wounds Accidents Medical Treatment Fractures dislocations and amputations revealed in bones Trephining Prehistoric surgery Large holes cut into skull Cause of death if it affected bones Diseases that affect bones General health and nutrition Whitehead et al 2005 247 Rickets dietary cause Growth Arrest Lines AKA Harris lines Lengthwise growth of child s long bones halted during periods of malnutrition When nutrition restored bones recommence growing Interruption marked by horizontal lines at ends of long bones Enamel Hypoplasia Buds of adult teeth susceptible to health and nutrition problems of early childhood Permanently scarred from malnutrition Presence of growth lines and or enamel hypoplasia provides direct evidence of dietary problems Diet You are what you eat The isotopes you ingest become part of your bones C12 C13 C14 heavy carbon isotopes C14 is unstable used for dating C12 and C13 are stable used to tell about your diet DIET Plants have different photosynthetic pathways resulting in different isotopes of carbon For example maize is a tropical plant that produces C13 whereas wheat is a temperate plant that produces C12 If you ate wheat but no maize or maize but no wheat we could tell from the ratio of C12 to C13 in your bones Diet Other isotopes and elements are also used to tell about diet Heavy nitrogen N isotopes ratio of C to N speaks to carnivorous vegetarian Elements such as strontium Cultural practices Whitehead et al 2005 235 Genetic relationship Parietal foramina on both sides of the sagittal suture Whitehead et al 2005 252 Could reconstruct face if know ethnicity John Gurche What can we learn from a population of skeletons Paleodemography basic population statistics to understand the structure of the population Mean life span age at which half dead half alive Sex ratio Looking at population better than just one individual gives you idea of range of variation for that population Paleopathology diseases
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