title: The Paternal Provisioning Hypothesis: effects of workload and testosterone production on men's musculature.
abstract: OBJECTIVE
  Testosterone supports male reproduction through a broad range of behavioral and physiological effects, including the maintenance of sexually dimorphic muscle used in male-male competition. Although it is often assumed that a persistent relationship exists between men's testosterone production and musculature, most studies either fail to find evidence for such a relationship, or document very weak associations. In nonhuman primates, by contrast, correlations between testosterone and muscle mass are higher. Here, we propose the "Paternal Provisioning Hypothesis," which predicts that men's skeletal muscle is less dependent on the effects of androgens than that of other primates, and more sensitive to the physical demands of men's work. This permits human fathers to downregulate testosterone, which has negative impacts on pair-bonding and parenting effort, but without sacrificing the strength and musculature necessary to provision mates and offspring.
  
  
  METHODS
  We tested predictions of the Paternal Provisioning Hypothesis by assessing parental status, salivary testosterone levels, anthropometry, and strength among 122 men (ages 18-78) at the Mogielica Human Ecology Study Site in rural Poland. We chose this population because men practice subsistence agriculture, regularly engaging in physically demanding labor. Grip and chest strength were assessed using a dynamometer, and upper-body musculature was estimated from arm muscle circumference.
  
  
  RESULTS
  In this population, testosterone showed no association with measures of strength or musculature, and was lower in older men and pair-bonded fathers. Marital and parental status and workload, by contrast, were positive predictors of muscle mass and strength measures.
  
  
  CONCLUSIONS
  These findings offer support for the Paternal Provisioning Hypothesis.
authors.affiliation: Department of Anthropology, University of New Mexico, Albuquerque, 87131, NM.
authors.forename: Louis Calistro
authors.initials: LC
authors.lastname: Alvarado
authors.affiliation: Department of Anthropology, University of New Mexico, Albuquerque, 87131, NM.
authors.forename: Martin N
authors.initials: MN
authors.lastname: Muller
authors.affiliation: Department of Anthropology, University of New Mexico, Albuquerque, 87131, NM.
authors.forename: Melissa
authors.initials: M
authors.lastname: Emery Thompson
authors.affiliation: Department of Environmental Health, Jagiellonian University, 31-007, Kraków, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Klimek
authors.affiliation: Department of Environmental Health, Jagiellonian University, 31-007, Kraków, Poland.
authors.forename: Ilona
authors.initials: I
authors.lastname: Nenko
authors.affiliation: Department of Environmental Health, Jagiellonian University, 31-007, Kraków, Poland.
authors.forename: Grazyna
authors.initials: G
authors.lastname: Jasienska
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D005220:Fathers / Q000706:statistics & numerical data; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D011044:Poland / Q000453:epidemiology; D012463:Saliva / Q000737:chemistry; D013739:Testosterone / Q000032:analysis*; D055815:Young Adult
chemical_list: D013739:Testosterone
keywords: men's life history; muscle mass; parental investment; steroid physiology; workload