TY - JOUR
T1 - Intralocus sexual conflict in humans: Physically and hormonally masculine individuals have more attractive brothers relative to sisters
AU - Garver-Apgar, C.E
AU - Heap, G.A.
AU - Tybur, J.M.
AU - Emery-Thompson, M.
PY - 2011
Y1 - 2011
N2 - Intralocus sexual conflict (IASC) occurs when sex-specific selection favors genes that increase fitness in one sex and decrease fitness in the other sex. The current study was designed to explore whether IASC occurs in humans. In a sample of siblings, we identified and measured sexually dimorphic traits and hormones within each sex that are related to fitness and are likely coded for by antagonistic genes: waist-to-hip ratio (WHR) and breast size in women, WHR and bicep size (an index of muscularity) in men, and estradiol (E) and testosterone (T) in both sexes. If these traits and hormones are coded for by genes under IASC, masculine or feminine expression of traits and hormones should differentially predict brothers' and sisters' fitness. Consistent with an IASC model, both men and women who were physically masculine for their sex reported higher mate value brothers relative to sisters. Similarly, in normal-weight individuals, E levels positively predicted the mate value of sisters relative to brothers and T levels positively predicted the mate value of brothers relative to sisters. We found no evidence that individuals with indicators of high genetic quality (i.e., physically masculine men and physically feminine women) share high mate value with all siblings, regardless of sibling sex. Results are novel and demonstrate for the first time that intralocus conflict in humans may influence the fitness of related individuals. © 2011 Elsevier Inc.
AB - Intralocus sexual conflict (IASC) occurs when sex-specific selection favors genes that increase fitness in one sex and decrease fitness in the other sex. The current study was designed to explore whether IASC occurs in humans. In a sample of siblings, we identified and measured sexually dimorphic traits and hormones within each sex that are related to fitness and are likely coded for by antagonistic genes: waist-to-hip ratio (WHR) and breast size in women, WHR and bicep size (an index of muscularity) in men, and estradiol (E) and testosterone (T) in both sexes. If these traits and hormones are coded for by genes under IASC, masculine or feminine expression of traits and hormones should differentially predict brothers' and sisters' fitness. Consistent with an IASC model, both men and women who were physically masculine for their sex reported higher mate value brothers relative to sisters. Similarly, in normal-weight individuals, E levels positively predicted the mate value of sisters relative to brothers and T levels positively predicted the mate value of brothers relative to sisters. We found no evidence that individuals with indicators of high genetic quality (i.e., physically masculine men and physically feminine women) share high mate value with all siblings, regardless of sibling sex. Results are novel and demonstrate for the first time that intralocus conflict in humans may influence the fitness of related individuals. © 2011 Elsevier Inc.
U2 - 10.1016/j.evolhumbehav.2011.03.005
DO - 10.1016/j.evolhumbehav.2011.03.005
M3 - Article
SN - 1090-5138
VL - 32
SP - 423
EP - 432
JO - Evolution and Human Behavior
JF - Evolution and Human Behavior
ER -