Measuring Finger Ratios in Hands and Bones: Testing the Reliability and Accuracy of Post-mortem Methods of Second-to-Fourth Digit Ratio Assessment in Primates

Presenter: Josie Beavers

Co-Presenters: Enrique Gomez

Faculty Mentor: Frances White, Stephen Frost

Presentation Type: Poster 46

Primary Research Area: Science

Major: Biological Anthropology

The ratio of length of the second digit to fourth digit indicates individual exposure to gonadal hormones in utero (Manning 2002). 2D:4D is therefore used as a proxy for prenatal androgen exposure; a lower 2D:4D indicates more prenatal androgen exposure, and a higher 2D:4D indicates less prenatal androgen exposure (Manning 2002). The most accurate way to measure 2D:4D is to measure from the proximal crease to the most distal end of the digit in living and recently deceased individuals (Manning 2002). However, in many cases an individual may be mummified or decomposed prior to measuring 2D:4D. Our research seeks to determine the accuracy of different 2D:4D measurement methods by comparing obtained 2D:4D values from the fully fleshed, skinned, disarticulated, and articulated phalangeal bones of the same rhesus macaque individual (Macaca mulatta). We also determined if the position of the hand (i.e. flattened palm or curled fingers) yielded significantly different 2D:4D ratios. Our findings indicate that the 2D:4D values obtained in all flattened measurements closely correlated (r = 0.997 – 0.999), but the measurements obtained from the curled hands were not as closely correlated (r = 0.962 – 0.982). These results suggest that 2D:4D measurements on articulated bones are most closely correlated to the fully fleshed 2D:4D measurement. These findings will allow scientists to more accurately obtain 2D:4D measurements on non-living specimens in the future.

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