Estimation of Ancestry 11 5 PDF

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Summary

Estimation of Ancestry: Lecture Notes, Examples, Practice Work...

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Estimation of Ancestry “Race”: Is It A Valid Concept? ●

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The term “race” is defined as “a division of a species that differs from other divisions by the frequency with which certain hereditary traits appear among its members” ○ Different populations of species have certain characteristics that other populations do not have In the past, anywhere from three (3) to fifty (50) distinct races have been described Is race a valid concept biologically?

Problems With the “Race” Concept: ● ● ● ●

The number of races cannot be agreed upon Continuous Variation: traits do not naturally divide themselves into discrete categories Every trait will produce a different set of “racial” groupings Greater genetic variation between individuals of a population than between populations

Population Group and Ancestry ● ●

Population Group defines a group of people living in a geographic area at a certain time Ancestry refers to the geographic history of an individual - it can be defined broadly or it can be defined specifically (i.e. tracing an individual's family back to a specific village hundreds of years ago…)

Methods for Estimation of Ancestry ● ● ● ●

Dental characteristics Morphological characteristics of the cranial and postcranial skeleton Multi-regression formula/ FORDISC DNA, osteon counting

Dental Characteristics ● ● ●

Traits

Two (2) dental characteristics are found at high frequency among certain population groups 1. Carabelli's Cusp (85% in some European Populations) 2. Shovel Shaped Incisors (Asian and American Groups)

African American 1. Wide-set eye orbits 2. Alveolar Prognathism (example ~ PEN test/ African American: pen will tilt forward, asian = pen will be straight up) 3. Sagittal ridge (narrow skull, parietal bones will be elevated a bit?) 4. Generally, a long skull (Asian + Europeans = nasal guttering/ ridge/ nasal cil but in African Americans this is missing) European 1. Close-set eye orbits 2. Orthognathous face (pen should touch mandible, teeth and nasal spine // aka lack of prognathism) 3. Retreating Zygomatics (folding back) 4. Generally, a tall skull (large forehead) Asian / Native American 1. Projecting Zygomatics (short idstance between zygomatic and nasal bone?) 2. Edge-to-edge bite 3. Generally, a broad skull (brachiocephalic)

Postcranial Traits ● Best bones to use for estimating ancestry are the long bones ● Populations vary in the proportions of the long bones; allows the use of various indices to infer ancestry ● The curve of the femur is also useful for estimating ancestry Indices (lab 2 and four) Curve of the Femur African american - fairly straight White (european) - slight curvature (relativly close to proximal end) Asians/ Native Americans - curvature begins at mid shaft or distal end of femur Multiple Regression ● Combines a number of measurements simultaneously to produce an estimate of ancestry ● The most common method is Giles and Elliot, 1962; generates two factors, which when plotted, indicate ancestry...