Abstract The Challenge Hypothesis (Wingfield et al., 1990) originally focused on adult male
avian testosterone elevated in response to same-sex competition in reproductive contexts …

Care of infants is a hallmark of mammals. Whereas parental care by mothers is obligatory for
offspring survival in virtually all mammals, fathers provide care for their offspring in only an …

Humans are sexually dimorphic: men and women differ in body build and composition,
craniofacial structure, and voice pitch, likely mediated in part by developmental testosterone …

Across vertebrates, testosterone is an important mediator of reproductive trade-offs, shaping
how energy and time are devoted to parenting versus mating/competition. Based on early …

There is widespread concern in both the popular and academic literature that a surplus of
men in a population intensifies mating competition between men, particularly unpartnered …

Objective Male aging is characterized by a decline in testosterone (TS) levels with a
substantial variability between subjects. However, it is unclear whether differences in age …

Background Exposure to environmental pollution via different mechanisms is associated
with multiple endocrine dysfunctions. Organophosphate esters (OPEs) are endocrine …

Male testosterone (T) decreases in response to childbirth. Longitudinal support for this has
come from samples across cultures. In this study, we look at individual differences in this …

Objective Cross‐culturally, men's T declines in response to pairbonding and fatherhood, but
less is known about what happens to T during and after life history transitions that …

Sociosexuality is defined as an individual's interest in uncommitted sexual activity and can
be measured in terms of both psychological orientations and behavioral expression. In socio …