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Phenotypic variation and thermoregulation of the human hand

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cam.restrictionthesis_access_open
cam.supervisorStock, Jay
cam.thesis.confidentialfalse
cam.thesis.fundingfalse
dc.contributor.authorPayne, Stephanie
dc.contributor.orcidPayne, Stephanie [0000-0002-7173-9262]
dc.date.accessioned2018-11-21T10:13:48Z
dc.date.available2018-11-21T10:13:48Z
dc.date.issued2018-11-30
dc.date.submitted2018-05-21
dc.date.updated2018-11-20T16:58:48Z
dc.description.abstractThe hand has the highest surface area-to-volume ratio of any body part. This property offers the potential for the hand to serve an important function in thermoregulation through radiative heat loss. Theoretically, the capacity for heat loss may be influenced by hand and digit proportions, but the extent to which these proportions influence the hand’s radiative properties remains under-investigated. Although hand morphology is highly constrained by both integration and functional dexterity, phenotypic variation in hand and digit proportions across human populations shows broad ecogeographic patterns. These patterns have been associated with climate adaptation. However, the theory linking climate adaptation to such ecogeographic patterns is based on underlying assumptions relating to thermodynamic principles, which have not been tested in vivo. This study sought to determine the influence of hand and digit proportions on heat loss from the hands directly, the additional anthropometric factors that may affect this relationship, and the impact of variation in hand proportions on dexterity in the cold. The relationship between hand proportions and thermoregulation was tested through both laboratory-based investigation and a field study. The laboratory investigation assessed the relationship between hand proportions and heat loss, the influence of body size and composition on this relationship, and the effect of morphological variation on manual dexterity. Participants (N=114; 18-50 years of age), underwent a 3-minute ice-water hand-immersion. Thermal imaging analysis was used to quantify heat loss. Hand and digit proportions were quantified using 2D and 3D scanning techniques; body size and composition were measured using established anthropometric methods and bio-impedance analysis. After accounting for body size, hand width, digit-to-palm length ratio, and skeletal muscle mass were significant predictors of heat loss from the hand, whilsthand length and fat mass were not. A separate set of participants (N=40) performed a Purdue pegboard dexterity test before and after the immersion test, which demonstrated that digit width alone negatively correlated with dexterity. The field study tested whether phenotypic variation in upper limb proportions could be attributed to cold adaptation or selection for dexterity in living populations exposed to significant energetic stress. Upper limb segment lengths were obtained from participants (N=254; 18-59 years of age), from highland and lowland regions of the Nepalese Himalayas using established anthropometric methods, and relative hand proportions were assessed in relation to severe energetic stress associated with life at high altitude. Relative to height, hand length and hand width were not reduced with altitude stress, whilst ulna length was. This indicates that cold adaptation is not shaping hand proportions in this case, although phenotypic variation in other limb segments may be attributed to cold adaptation or a thrifty phenotype mechanism. The current study provides empirical evidence to support the link between surface area-to-volume ratio, thermodynamic principles and ecogeographical patterns in human hand morphology. However, this research also demonstrates the complexity of the hand’s role in thermoregulation; not only do other factors such as muscularity affect heat loss from the hand, but hand morphology is also highly constrained by integration and dexterity.
dc.description.sponsorshipTrinity Hall Studentship
dc.identifier.doi10.17863/CAM.32917
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/285561
dc.language.isoen
dc.publisher.collegeTrinity Hall
dc.publisher.departmentDepartment of Archaeology
dc.publisher.institutionUniversity of Cambridge
dc.rightsAll rights reserved
dc.rightsAll Rights Reserveden
dc.rights.urihttps://www.rioxx.net/licenses/all-rights-reserved/en
dc.subjectHand
dc.subjectdexterity
dc.subjectthermal imaging
dc.subjectHimalayas
dc.subjectsurface area-to-volume ratio
dc.subjectcold
dc.subjectice-water immersion
dc.subjecttemperature
dc.subjectradiation
dc.subjectheat loss
dc.subjectdigits
dc.subjectproportions
dc.subjectecogeographic patterns
dc.subjectphenotypic variation
dc.subjectclimate adaptation
dc.subjectanthropometry
dc.subjectbody size
dc.subjectmuscle mass
dc.subjectenergetic stress
dc.subjectthrifty phenotype
dc.titlePhenotypic variation and thermoregulation of the human hand
dc.typeThesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnameDoctor of Philosophy (PhD)
dc.type.qualificationtitlePhD in Biological Anthropology

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