The good genes sexual selection controversy: Does the Handicap Principal apply to modern humans?

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In 2017, an early version of this application received 'strong' across all categories and 'moderate' under merit of the proposal. As a result, I was awarded a two-year NSERC Discovery Development Grant (DDG) to foster development of the proposal toward full funding. I have since collected a large pilot study exploring the role of immune markers in predicting male secondary sexual characteristics. I have published groundwork for this proposal (Evolution and Human Behavior, IF=3.62) linking salivary Immunoglobulin-A to vocal masculinity.  I have also refined the application by proposing two new studies and incorporating the exploration of gene-immune marker interactions in predicting secondary sex characteristics. I also utilised my DDG funding to become trained in phlebotomy in order to maximise future funding use efficiency, highlighting my dedication to this important body of work. Ancestors who could identify healthy mates were at a substantial reproductive advantage. Of course, immune function cannot be observed directly. Rather, good-genes sexual selection hypothesis proposes that individuals rely on morphological cues to inform a potential mate's immunocompetence (Sugiyama, 2005). In turn, organisms might compete for mates by advertising their 'good genes' via traits that are immunologically-costly to produce (Zahavi, 1975). This immunocompetence handicap hypothesis (ICHH) is one of the most cited hypotheses in all of evolutionary biology. Yet disconcertingly, empirical evidence supporting a link between secondary sex characteristics and immune function is weak (Hamilton especially among humans.  The proposed program of research addresses this fundamental gap in knowledge by systematically assessing: 1) whether putative costly-to-develop secondary sex characteristics (e.g., male vocal and facial masculinity; height) do indeed indicate underlying immunocompetence at either the genetic (major histocompatability) or functional (innate and adaptive immunity) levels, 2) whether uniquely female secondary sexual traits (vocal and facial femininity, breast size and shape) inform immunocompetence, fertility, or both, 3) whether immune function pre-puberty predicts sex hormone-mediated development of secondary sex traits, whether parental secondary sexual characteristics actually predict offspring immunocompetence, and 4) whether female perceptions of male attractiveness inform their underlying immunocompetence. Together, this ambitious yet high-feasibility  program will provide the first comprehensive examination of diverse multi-level markers of immune function  in relation to prominent human secondary sexual characteristics. It will be the first large-scale test of  the ICHH in humans. Evidence from these studies will transform the field's understanding of sexual selection in humans by either supporting or calling into question one of the most widely-cited, yet poorly evidenced, hypotheses in contemporary evolutionary theory.