An alternative hypothesis for the evolution of same-sex sexual behaviour in animals

@article{Monk2019AnAH,
  title={An alternative hypothesis for the evolution of same-sex sexual behaviour in animals},
  author={Julia D. Monk and Erin Giglio and Ambika Kamath and Max R. Lambert and Caitlin E. McDonough},
  journal={Nature Ecology \& Evolution},
  year={2019},
  volume={3},
  pages={1622 - 1631}
}
Same-sex sexual behaviour (SSB) has been recorded in over 1,500 animal species with a widespread distribution across most major clades. Evolutionary biologists have long sought to uncover the adaptive origins of ‘homosexual behaviour’ in an attempt to resolve this apparent Darwinian paradox: how has SSB repeatedly evolved and persisted despite its presumed fitness costs? This question implicitly assumes that ‘heterosexual’ or exclusive different-sex sexual behaviour (DSB) is the baseline… 

Same-sex sexual behaviour and selection for indiscriminate mating

A model of sexual reproduction is built and created, showing that indiscriminate mating is the optimal strategy under a wide range of conditions and supporting the hypothesis that same-sex sexual behaviour can be maintained by selection for indiscriminate sexual behaviour.

Understanding same-sex sexual behaviour requires thorough testing rather than reinvention of theory

This paper argues that an alternative hypothesis for same-sex sexual behaviour (SSB), whereby an ancestral condition of indiscriminate sexual behaviour would have led to the evolution of SSB in various lineages is outlined, and proposes that rather than reinventing theory, a thorough testing of existing hypotheses is needed.

Same-sex sexual behavior and selection for indiscriminate mating

A simple model of sexual reproduction is built and it is shown that indiscriminate mating is the optimal strategy under a wide range of conditions, which provides strong support for the hypothesis that SSB is likely maintained by selection for indiscriminate sexual behavior.

Ancestral sex-role plasticity facilitates the evolution of same-sex sexual behaviour

Data-based simulations confirmed that socially-cued plasticity contributes to pair maintenance because dimorphic movements improve reunion success upon accidental separation and may be of widespread importance to the evolutionary maintenance of SSB.

Genomic evidence consistent with antagonistic pleiotropy may help explain the evolutionary maintenance of same-sex sexual behaviour in humans.

It is shown that genetic effects associated with SSB may, in individuals who only engage in opposite-sex sexual behaviour (OSB individuals), confer a mating advantage, and computer simulations suggest that such a mating advantages could help explain how SSB has been evolutionarily maintained.

Ancestral primacy of same-sex sexual behaviour does not explain its stable prevalence in modern populations

The authors see this as a more parsimonious hypothesis compared to a traditional set, which sees current SSB as either a developmental error or conferring some indirect fitness benefits, and suggest that SSB expression is impacted by such factors as sex ratios, encounter rates and other ecological causes.

Anecdotal observation of a sexual encounter between two male naked mole-rats

Evidence of same-sex sexual behaviours in two male naked mole-rats for the first time is presented and it is speculated that dispersing individuals may be indiscriminatory in their mating strategy, copulating with conspecifics regardless of sex, to counter the risk of missed reproductive opportunities.

Diversifying Displays of Biological Sex and Sexual Behaviour in a Natural History Museum

Abstract Many natural history museums present species’ life histories in their galleries, which millions of visitors use to make meaning of the ‘natural world’ to which humans belong. Because

Darwin, sexual selection, and the brain

  • M. Ryan
  • Psychology, Biology
    Proceedings of the National Academy of Sciences
  • 2021
Progress is reviewed in the understanding of Darwin's conjecture of “a taste for the beautiful” by considering research from these diverse fields that have conspired to provide unparalleled insight into the chooser’s mate choices.

Sex-Biased Mortality and Sex Reversal Shape Wild Frog Sex Ratios

It is found that sex-biased mortality influences sex ratios within a population, and the findings imply that genotypic sex- biased mortality during tadpole development affects phenotypesic sex ratio variation at metamorphosis.

References

SHOWING 1-10 OF 116 REFERENCES

A test of genetic models for the evolutionary maintenance of same-sex sexual behaviour

An unexpected and strong paternal effect on the expression of SSB is found, suggesting possible Y-linkage of the trait and informing evolutionary genetic mechanisms that might maintain low but persistently observed levels of male SSB in D. melanogaster.

Same-sex sexual behavior in insects and arachnids: prevalence, causes, and consequences

Evidence is provided for same-sex sexual behavior in ~110 species of insects and arachnids based on mistaken identification and is probably maintained because the cost of rejecting a valid opportunity to mate with a female is greater than that of mistakenly mating with a male.

Same-sex sexual behavior and evolution.

High male sexual investment as a driver of extinction in fossil ostracods

Ostracod species (small, bivalved crustaceans) with high sexual dimorphism, and therefore high male investment, had markedly higher extinction rates than low-investment species, indicating that sexual selection can be a substantial risk factor for extinction.

Acceptance threshold theory can explain occurrence of homosexual behaviour

The results support the idea that in animal species, in which the recognition cues of females and males overlap to a certain degree, SSB is a consequence of an adaptive discrimination strategy to avoid the costs of making rejection errors.

Sexually antagonistic selection on genetic variation underlying both male and female same-sex sexual behavior

This study provides experimental support for the hypothesis that widespread pleiotropy generates pervasive intralocus sexual conflict governing the expression of SSBs, suggesting that SSB in one sex can occur due to the expressionof genes that carry benefits in the other sex.
...