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Teeth and Skull: Function and Variation

Explore the function of teeth and how they provide evidence for age, sex, health, and evolutionary relationships. Learn about measuring human biological variation and the correlation between body proportions and climate.

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Teeth and Skull: Function and Variation

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  1. Lab 6 & 8 Today, lets do part of dentition, exercise 8 Then Exam 1 prep

  2. Evidence from teeth and skull • Agnathans: first vertebrates, had no teeth or jaws • Because we’re mammals, we have heterodont teeth • Form of teeth reflects function of animal’s diet • Teeth are most common fossil found and tell: • Age • Sex • Health • Mating systems • Behaviors • Evolutionary relationships • Diet

  3. Tooth function • Aid the digestive system • Anterior dentition (incisors and canines) is responsible for digestion and posterior dentition (premolars and molars) physically process food, called mechanical digestion • For many mammals, anterior teeth have other functions • Grooming, threat displays, fighting

  4. Tooth function • For mechanical digestion, there are 4 types: • Puncture/piercing (insects) • Small, sharp, needle-like • Shearing (leaves) • One side of molars is higher and sharper than the other • Crushing/grinding (fruit/omnivore) • Rounded, worn-down cusps • Tearing (meat) • Interlocking triangles

  5. Measuring Human Biological Variation • Anthropometry: measurement of humans • Osteometry: measurement of skeletons

  6. Anthropometry • Racist history • American Anthropological Association • 1930’s Franz Boaz, others • No differences in intelligence, athletic ability between races • Science offers limited definition of race • http://www.understandingrace.org/history/index.html

  7. Human morphology varies Human physiology varies Human behavior varies Caused by: Genes (inherited from parents) Environment ALWAYS interact! Humans are adapted to have lots of variation

  8. How do we measure variation? 1) biochemical: we can find evidence of gene flow and/or natural selection by looking at allele frequencies. 2) genetic distance data: the average measure of relatedness based on a number of traits. 3) demographic measures: e.g. migration patterns, birth and mortality rates 4) environmental correspondence: when looking for evidence of the effects of natural selection 5) anthropometrics: height, weight, and other measurements

  9. M. fuscata, Japan M. sinica, Sri Lanka Natural Selection shapes body proportions • Animals in cold places are large and stocky, with short limbs • Animals in hot places are smaller, thinner, longer limbed

  10. Femur Tibia Contemporary human populations reflect this principle • Reduction of surface area  less heat lost • Increase in body volume  more heat produced • Body proportions are associated with climate • Crural index = tibia/femur ratio • Crural index correlated with height

  11. People in warm climates tend to have long limbs in proportion to height

  12. Lets Get Down to Business; Measuring • Metric system!!! • Millimeters!!! • Don’t round off • 8.1 • Standing height • Sitting height • Popliteal height (PH) • Seat height

  13. 8.1 Comparing bodies to furniture: Do we fit? • Comfortable range for knee when sitting • Leg shouldn’t be hanging • Knees shouldn’t be up too high • Seat height needs to fall within that range to be good fit Ah, just right! Ouch!

  14. 8.1 Comparing bodies to furniture: Do we fit? • PH + 3 cm = height of knees • Minimum angle of knees = (PH + 3cm) * 0.866 = PHmin • Maximum angle of knees = (PH + 3 cm) * 0.996 = Phmax • Seat height needs to fall between the PHmin – PHmax range for comfort Ah, just right! Ouch!

  15. Lab Groups • May work in all male/all female groups OR • KEEP data by sex separate • We will use the wooden chair for Seat Height • Enter your data in the table on the board

  16. The Plan • For Exercise 6, just do 6.1 and read pgs. 63-64 • Exercise 8, enter data into Excel file • Work on the Handout, for exam prep for bones. • Each group has been given a box of bones to work with

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