Evolution and human sexuality

Psychosexual development, sexual functioning and sexual satisfaction in long-term childhood cancer survivors: DCCSS-LATER 2 sexuality substudy

OBJECTIVES

Childhood cancer may negatively impact childhood cancer survivors' (CCS) sexuality. However, this is an understudied research area. We aimed to describe the psychosexual development, sexual functioning and sexual satisfaction of CCS, and identify determinants for these outcomes. Secondarily, we compared the outcomes of a subsample of emerging adult CCS to the Dutch general population.

METHODS

From the Dutch Childhood Cancer Survivor Study LATER cohort (diagnosed 1963-2001), 1912 CCS (18-71 years, 50.8% male) completed questions on sexuality, psychosocial development, body perception, mental and physical health. Multivariable linear regressions were used to identify determinants. Sexuality of CCS age 18-24 (N = 243) was compared to same-aged references using binomial tests and t-tests.

RESULTS

One third of all CCS reported hindered sexuality due to childhood cancer, with insecure body the most often reported reason (44.8%). Older age at study, lower education, surviving central nervous system cancer, poorer mental health and negative body perception were identified as determinants for later sexual debut, worse sexual functioning and/or sexual satisfaction. CCS age 18-24 showed significantly less experience with kissing (p = 0.014), petting under clothes (p = 0.002), oral (p = 0.016) and anal sex (p = 0.032) when compared to references. No significant differences with references were found for sexual functioning and sexual satisfaction, neither among female CCS nor male CCS age 18-24.

CONCLUSIONS

Emerging adult CCS reported less experience with psychosexual development, but similar sexual functioning and sexual satisfaction compared to references. We identified determinants for sexuality, which could be integrated in clinical interventions for CCS at risk for reduced sexuality.

Sexual dysfunction and disorders as a consequence of infertility: a systematic review and meta-analysis

BACKGROUND

Sexuality has a key impact on quality of life and on reproductive health. Infertility often results in sexual dysfunction. Despite this close association, addressing sexuality is not a standard component of infertility counselling, especially since in most countries sexual medicine is not a core element of specialist training. Even today, many doctors and patients consider discussing sexuality to be more challenging than other aspects of reproductive medicine. The present review addresses the complex consequences of infertility on sexuality.

OBJECTIVE AND RATIONALE

Our goals were: (i) to identify the prevalence of sexual problems resulting from infertility, (ii) to evaluate characteristics of sexual difficulties and disorders resulting from infertility and (iii) to analyse factors involved in the complex association between sexual problems and infertility.

SEARCH METHODS

A systematic search for publications containing keywords related to sexual disorders and infertility was performed via PubMed, Web of Science and Psyndex. A total of 170 manuscripts published between January 1966 and April 2021 were identified after verification of inclusion and exclusion criteria. The reference lists in these manuscripts were searched for further relevant literature. Studies were reviewed for quality-related methodological details.

OUTCOMES

Couples diagnosed with infertility have an increased risk of sexual disorders. Loss of sexual desire and erectile dysfunction are among the most frequent sexual disorders resulting from infertility. Currently available literature reflects only fragmentarily the complexity of the diverse interactions. Sexuality plays out against the backdrop of interactions among personal, cultural, infertility-related and sexuality-related factors. Considering this complexity, it is crucial to evaluate individual profiles as well as partnership interactions to avoid a negative impact of infertility on a couple's sexual life.

WIDER IMPLICATIONS

Identifying sexual disorders as relevant considerations in the context of infertility and exploring their impact during the entire course of diagnosis and treatment constitute an important contribution to comprehensively care for the couples concerned. Counselling should focus on preventing the onset and aggravation of sexual disorders. As sexuality represents a major component of quality of life and of partnership, such support may improve not only the current overall wellbeing but also the chances of a satisfactory long-term partnership and family life.

Why People Keep an Intimate Relationship : Investigating Ultimate and Proximate Reasons

Forming long-term intimate relationships constitutes an important aspect of human nature. Within the context of an evolutionary theoretical framework, the current research has attempted to investigate what motivates people to keep an intimate relationship. Using a combination of qualitative research methods in a sample of 131 Greek-speaking participants, 58 reasons that motivated individuals to keep their intimate relationship were identified. Using quantitative research methods in a sample of 789 Greek-speaking participants who were in an intimate relationship, these reasons were classified in nine broad factors and two broader domains. Having a supporting and compatible partner with whom one shares similar goals, and with whom one has good sex and a strong emotional attachment, were rated among the most important factors motivating participants to keep their relationship. Moreover, as indicated by the domain means, participants were more strongly motivated to keep their intimate relationship if their partners had desirable attributes, such as providing them with support, and less so by their own attributes, such as fear of loneliness. Significant effects of sex, age, marital status, presence of children, and years in a relationship were found for several factors.

Changes in prenatal testosterone and sexual desire in expectant couples

During the transition to parenthood (TTP), both women and men report declines in sexual desire, which are thought to reflect an evolutionarily adaptive focus on parenting over mating. New parents also show changes in testosterone, a steroid hormone implicated in both parenting and mating, suggesting that changes in sexual desire may be associated with changes in testosterone. To test these associations, we followed a sample of heterosexual couples expecting their first child across the prenatal period. We examined prenatal changes in testosterone and two forms of sexual desire (solitary, dyadic). Expectant mothers showed prenatal increases in testosterone, and women's higher testosterone was associated with lower dyadic desire. Expectant fathers showed prenatal decreases in testosterone, and declines in men's testosterone were associated with lower dyadic desire. Testosterone was unrelated to men's or women's solitary desire. Our findings provide support for the idea that prenatal changes in testosterone contribute to an evolutionarily adaptive focus on parenting over mating during the TTP.

A Close and Supportive Interparental Bond During Pregnancy Predicts Greater Decline in Sexual Activity From Pregnancy to Postpartum: Applying an Evolutionary Perspective

A common topic for advice given to parents after childbirth – both from relationship experts and popular media – is how to “bounce back” to one’s pre-pregnancy sexuality, with warnings that postpartum declines in sexual frequency will take a serious toll on one’s relationship. However, these admonishments may not accurately reflect the ways in which the unique reproductive context of pregnancy and the postpartum transition alter associations between sexual frequency and relationship quality. Evolutionary perspectives on reproductive strategies would suggest that in the postpartum context, decreased sexual activity would help target parental investment in the current offspring (rather than creating new offspring); however, if the parental relationship is lacking in intimacy and support, continued sexual activity may help seal the cracks in the bond. We tested this theory in a longitudinal dyadic study of changes in relationship quality and sexual frequency from pregnancy to 6 months postpartum among 159 heterosexual couples. We found that across three different measures of relationship quality taken from interviews and behavioral observation of couple interactions, higher relationship quality (i.e., greater support, intimacy, and responsiveness) predicted greater decline in sexual frequency whereas sexual frequency remained relatively stable in lower quality relationships. These findings suggest that, during the postpartum transition, decreased sexual frequency may not be a reliable signal of poor relationship quality.

Mate Preferences and Their Behavioral Manifestations

Evolved mate preferences comprise a central causal process in Darwin's theory of sexual selection. Their powerful influences have been documented in all sexually reproducing species, including in sexual strategies in humans. This article reviews the science of human mate preferences and their myriad behavioral manifestations. We discuss sex differences and sex similarities in human sexual psychology, which vary according to short-term and long-term mating contexts. We review context-specific shifts in mating strategy depending on individual, social, and ecological qualities such as mate value, life history strategy, sex ratio, gender economic inequality, and cultural norms. We review the empirical evidence for the impact of mate preferences on actual mating decisions. Mate preferences also dramatically influence tactics of mate attraction, tactics of mate retention, patterns of deception, causes of sexual regret, attraction to cues to sexual exploitability, attraction to cues to fertility, attraction to cues to resources and protection, derogation of competitors, causes of breakups, and patterns of remarriage. We conclude by articulating unresolved issues and offer a future agenda for the science of human mating, including how humans invent novel cultural technologies to better implement ancient sexual strategies and how cultural evolution may be dramatically influencing our evolved mating psychology.

Testosterone and Jamaican Fathers : Exploring Links to Relationship Dynamics and Paternal Care

This paper investigates relationships between men's testosterone and family life in a sample of approximately 350 Jamaican fathers of children 18-24 months of age. The study recognizes the role of testosterone as a proximate mechanism coordinating and reflecting male life history allocations within specific family and cultural contexts. A sample of Jamaican fathers and/or father figures reported to an assessment center for an interview based on a standardized questionnaire and provided a saliva sample for measuring testosterone level. Outcomes measured include subject demographics such as age and relationship status as well as partnership quality and sexuality and paternal attitudes and behavior. The variation in these fathers' relationship status (e.g., married co-residential fathers, fathers in new non-residential relationships) was not associated with men's testosterone. Too few stepfathers participated to enable a direct test of the prediction that stepfathers would have higher testosterone than biological fathers, although fathers who reported living with partners' (but not his own) children did not have higher testosterone than fathers not reporting residing with a non-biological child. Fathers' relationship quality was negatively related to their testosterone. Measures of paternal attitudes and behavior were not related to fathers' testosterone. Consistent with previous ethnography, this sample of Jamaican fathers exhibited variable life history profiles, including residential status. We discuss why fathers' relationship quality was found to be negatively related to their testosterone level, but other predictions were not upheld.

Humans as a model species for sexual selection research

Ever since Darwin, questions about humans have driven sexual selection research. While studies of other organisms are often justified as useful for improving understanding of humans, humans themselves can be useful models. Although humans present some drawbacks as model organisms (complicated societies, slow reproduction and strong ethical constraints on experimental options), humans nonetheless offer many advantages (being abundant, accessible and having detailed historical records for some populations). As an additional challenge, humans exhibit a rather puzzling combination of traits. Some traits (pair-bonding, biparental care and modest sexual dimorphism in body size) suggest selection for monogamous mating, while other traits (including sexual dimorphism in body composition and appearance) suggest selection for polygyny. Such puzzles have motivated research on other species, resulting in a rich set of comparative data that provides insights into humans and other species. Recent studies of visual trait dimorphism suggest that human appearance reflects adaptation for multi-level societies, rather than high levels of polygyny. In addition to biological traits, human cultural traits have undergone rapid evolution. Changes in subsistence strategies profoundly affect opportunities for sexual selection. The enormous variability of human behaviour and ecology provides abundant opportunities to test key hypotheses, and poses challenging puzzles for future research.

A review of human male field studies of hormones and behavioral reproductive effort

The purpose of this paper is to review field studies of human male hormones and reproductive behavior. We first discuss life history theory and related conceptual considerations. As illustrations, distinctive features of human male life histories such as coalitional aggression, long-term partnering and paternal care are noted, along with their relevance to overall reproductive effort and developmental plasticity. We address broad questions about what constitutes a human male field study of hormones and behavior, including the kinds of hormone and behavioral measures employed in existing studies. Turning to several sections of empirical review, we present and discuss evidence for links between prenatal and juvenile androgens and sexual attraction and aggression. This includes the proposal that adrenal androgens-DHEA and androstenedione-may play functional roles during juvenility as part of a life-stage specific system. We next review studies of adult male testosterone responses to competition, with these studies emphasizing men's involvement in individual and team sports. These studies show that men's testosterone responses differ with respect to variables such as playing home/away, winning/losing, and motivation. Field studies of human male hormones and sexual behavior also focus on testosterone, showing some evidence of patterned changes in men's testosterone to sexual activity. Moreover, life stage-specific changes in male androgens may structure age-related differences in sexual behavior, including decreases in sexual behavior with senescence. We overview the considerable body of research on male testosterone, partnerships and paternal care, noting the variation in social context and refinements in research design. A few field studies provide insight into relationships between partnering and paternal behavior and prolactin, oxytocin, and vasopressin. In the third section of the review, we discuss patterns, limitations and directions for future research. This includes discussion of conceptual and methodological issues future research might consider as well as opportunities for contributions in under-researched male life stages (juvenility, senescence) and hormones (e.g., vasopressin).

Female sexual dysfunction (FSD): Prevalence and impact on quality of life (QoL)

Female sexual dysfunction (FSD) and quality of life (QOL) are both multidimensional and have a bidirectional relationship across the reproductive life span and beyond. Methodological difficulties exist in estimating the real prevalence of FSD because it is hard to determine the level of distress associated with sexual symptoms in a large-scale survey. Approximately 40-50% of all women report at least one sexual symptom, and some conditions associated with hormonal changes at menopause, such as vulvovaginal atrophy (VVA) and hypoactive sexual desire disorder (HSDD), have a significant impact on sexual function and QOL. Sexual distress peaks at midlife, declines with age and is strongly partner-related. Many postmenopausal women are still sexually active, especially if they are in a stable partnership. Even though sexual functioning is impaired, a variety of psychosocial factors may maintain sexual satisfaction. That being so, health care providers (HCPs) should proactively address sexual symptoms at midlife and in older women, from a balanced perspective. Adequate counselling should be offered. Women with distressing symptoms may benefit from tailored hormonal and non-hormonal therapies, whereas women without distress related to their sexual experiences should not receive any specific treatment.

Sleep intensity and the evolution of human cognition

Over the past four decades, scientists have made substantial progress in understanding the evolution of sleep patterns across the Tree of Life. Remarkably, the specifics of sleep along the human lineage have been slow to emerge. This is surprising, given our unique mental and behavioral capacity and the importance of sleep for individual cognitive performance. One view is that our species' sleep architecture is in accord with patterns documented in other mammals. We promote an alternative view, that human sleep is highly derived relative to that of other primates. Based on new and existing evidence, we specifically propose that humans are more efficient in their sleep patterns than are other primates, and that human sleep is shorter, deeper, and exhibits a higher proportion of REM than expected. Thus, we propose the sleep intensity hypothesis: Early humans experienced selective pressure to fulfill sleep needs in the shortest time possible. Several factors likely served as selective pressures for more efficient sleep, including increased predation risk in terrestrial environments, threats from intergroup conflict, and benefits arising from increased social interaction. Less sleep would enable longer active periods in which to acquire and transmit new skills and knowledge, while deeper sleep may be critical for the consolidation of those skills, leading to enhanced cognitive abilities in early humans.

Disruption of parenting behaviors in california mice, a monogamous rodent species, by endocrine disrupting chemicals

The nature and extent of care received by an infant can affect social, emotional and cognitive development, features that endure into adulthood. Here we employed the monogamous, California mouse (Peromyscus californicus), a species, like the human, where both parents invest in offspring care, to determine whether early exposure to endocrine disrupting chemicals (EDC: bisphenol A, BPA; ethinyl estradiol, EE) of one or both parents altered their behaviors towards their pups. Females exposed to either compound spent less time nursing, grooming and being associated with their pups than controls, although there was little consequence on their weight gain. Care of pups by males was less affected by exposure to BPA and EE, but control, non-exposed females appeared able to “sense” a male partner previously exposed to either compound and, as a consequence, reduced their own parental investment in offspring from such pairings. The data emphasize the potential vulnerability of pups born to parents that had been exposed during their own early development to EDC, and that effects on the male, although subtle, also have consequences on overall parental care due to lack of full acceptance of the male by the female partner.

Pseudogenization of testis-specific Lfg5 predates human/Neanderthal divergence

Recent reviews discussed the critical roles of apoptosis in human spermatogenesis and infertility. These reviews highlight the FasL-induced caspase cascade in apoptosis lending importance to our discovery of the pseudogene status of the Lfg5 gene in modern humans, Neanderthal and the Denisovan. This gene is a member of the ancient and highly conserved apoptosis Lifeguard family. This pseudogenization is the result of a premature stop codon at the 3'-end of exon 8 not found in any other ortholog. With the current exception of the domesticated bovine and buffalo, Lfg5's expression in mammals is testis-specific. A full analysis of this gene, its phylogenetic context and its recent hominin changes suggest its inactivation was likely under selection in human evolution.