Does human ejaculate quality relate to phenotypic traits?

Abstract

A given man's phenotype embodies cues of his ancestral ability to effectively defend himself and his kin from harm, to survive adverse conditions, and to acquire status and mating opportunities. In this review, we explore the hypothesis that a man's phenotype also embodies cues to fertility or the probability that an ejaculate will fertilize ova. Female mate choice depends on the ability to discern the quality of a male reproductive partner through his phenotype, and male fertility may be among the traits that females have evolved to detect. A female who selects as mates males that deliver higher quality ejaculates will, on average, be more fecund than her competitors. Data on several non-human species demonstrate correlations between ejaculate quality and secondary sexual characteristics that inform female mate choice, suggesting that females may select mates in part on the basis of fertility. While the non-human literature on this topic has advanced, the human literature remains limited in scope and there is no clear consensus on appropriate methodologies or theoretical positions. We provide a comprehensive review and meta-analysis of this literature, and conclude by proposing solutions to the many issues that impede progress in the field. In the process, we hope to encourage interest and insight from investigators in other areas of human mating and reproductive biology. Am. J. Hum. Biol. 28:318-329, 2016. © 2015 Wiley Periodicals, Inc.

Quality of seminal fluids varies with type of stimulus at ejaculation

“…The origins of such strong male effects are unclear. It has been suggested that reproductive parameters may reveal variance in health and vigour, but this hypothesis is little supported in humans34 (apart from several infertility aetiologies35 or the damaging effects of cigarette smoking and other life-style factors36) or in species with secondary sexual traits that may serve as quality indicators37. The housing conditions that our stallions experience at the stud are expected to minimize variance in health and vigour, and we found no correlations between reproductive parameters and stallion age or size.…”

The relationship between health and mating success in humans

“…Oxidative stress also negatively impacts immune function and sperm quality by damaging immune and sperm cells [16,19]. Finally, the phenotype-linked fertility hypothesis proposes that male signals provide information about semen quality [20,21], which is an indicator of male reproductive health and fertility, as well as more general health [22,23].…”

Life history correlates of human (Homo sapiens) ejaculate quality.

“…Research on human ejaculate quality has focused on testing the phenotype-linked fertility hypothesis on the assumption that ancestral men pursuing short-term mating would have produced higher quality ejaculates more capable of fertilizing ova (Jeffery et al, 2016). Guided by a life history perspective, however, the current results suggest that ejaculate quality accords more strongly with parenting effort than with mating effort (Simmons et al, 2017).…”

“…The results of the current study are preliminary. Additional research is needed to identify which phenotypic traits of men are reliably associated with ejaculate quality (see Jeffery et al, 2016, for an extended discussion) and to confirm whether ejaculate quality is reliably associated with other measures and indicators of life history strategies. Measurement of within-human variation of life history strategy has been the subject of debate since the data reported here were collected (Richardson et al, 2017).…”

“…Ejaculate quality may also be associated with phenotypic indicators of life history strategies. Human ejaculate quality has been shown in some studies to be correlated with men’s trait attractiveness (see Jeffery, Pham, Shackelford, & Fink, 2016, for a review). Trait attractiveness, in turn, has been shown to be correlated with relatively fast life history strategy indicators in humans, including greater number of offspring and greater number of sexual partners in traditional and contemporary populations (Jokela, 2009; Waynforth, 1998).…”