Dermatoglyphics, handedness sex, and sexual orientation

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  • 1. • Dermatoglyphics, Handedness Sex, and Sexual Orientation• Journal article by J. Michael Bailey, Sarah Kaspar, Brian S. Mustanski; Archives of Sexual Behavior, Vol. 31, 2002 Dermatoglyphics, handedness, sex, and sexual orientation by Brian S. Mustanski , J. Michael Bailey , Sarah Kaspar Brian S. Mustanski (1,3) J. Michael Bailey (2) Sarah Kaspar (2) INTRODUCTION A growing body of evidence implicates biological influences on the development of sexual orientation in humans. This evidence includes studies from a variety of disciplines: behavior genetics (Bailey & Pillard, 1991), molecular genetics (Hamer, Hu, Magnuson, Hu, & Pattatucci, 1993; Hu et al., 1995; see Rice, Anderson, Risch, & Ebers, 1999 for failed replication), neuroanatomy (Byne et al., 2001; LeVay, 1991), neuropsychology (McCormick & Witelson, 1991), endocrinology (Zucker et al., 1996), and anthropometry (Williams et al., 2000). However, there is still little understanding of the time period during which sexual orientation is programmed into the developing neural circuitry. Furthermore, the precise biological mechanisms remain controversial (Dyne & Parsons, 1993). One way to localize the timing of sexual orientation differentiation is to examine correlated characteristics for which the critical period of formation is known. This study focuses on dermatoglyphics and handedness as characteristics that may h elp in localizing the timing of sexual orientation differentiation and further inform the route through which it occurs. Furthermore, it represents an attempt to replicate and extend prior findings. Timing of Fingerprint Formation and Handedness Differentiation Skin ridges, or dermatoglyphics, are found on the palms and soles of all primates and, in humans, are determined between the 8th and 16th week of fetal life (Holt, 1968). In the postnatal period, the ridge patterns are not affected by development or the environment and can only be altered by severe mechanical damage (Cummins & Midlo, 1961), making them a good source of information about the timing of prenatal events that are correlated with their eventual pattern. At present, less is known about the timing of handedness development. Increasingly, however, handedness has been hypothesized to depend primarily on prenatal factors, such as genetics (Annett, 1985; Gangestad et al., 1996; McManus, 1985; Yeo, Gangestad, & Daniel, 1993) and prenatal or perinatal environmental events (Bishop, 1990; for a critical review see Searleman, Porac, & Coren, 1989). Indirect evidence for the early ontogeny of handedness includes studies of fetuses that disproportionately move their right hands (McCartney & Hepper, 1999) and suck their right thumbs (Hepper, Shahidullah, & White, 1991). Theoretical Associations Among Dermatoglyphic Asymmetry, Handedness, and Sexual Orientation Two distinct mechanisms might account for an association between sexual orientation and either dermatoglyphic asymmetry or handedness: neurohormonal influences and developmental instability. The most influential theory about the origins of sexual orientation is that homosexuality is caused by atypical androgen