The evolution of same-sex sexual behaviour in mammals - PubMed (original) (raw)

The evolution of same-sex sexual behaviour in mammals

José M Gómez et al. Nat Commun. 2023.

Abstract

Same-sex sexual behaviour has attracted the attention of many scientists working in disparate areas, from sociology and psychology to behavioural and evolutionary biology. Since it does not contribute directly to reproduction, same-sex sexual behaviour is considered an evolutionary conundrum. Here, using phylogenetic analyses, we explore the evolution of same-sex sexual behaviour in mammals. According to currently available data, this behaviour is not randomly distributed across mammal lineages, but tends to be particularly prevalent in some clades, especially primates. Ancestral reconstruction suggests that same-sex sexual behaviour may have evolved multiple times, with its appearance being a recent phenomenon in most mammalian lineages. Our phylogenetically informed analyses testing for associations between same-sex sexual behaviour and other species characteristics suggest that it may play an adaptive role in maintaining social relationships and mitigating conflict.

© 2023. Springer Nature Limited.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1

Fig. 1. Evolution of same-sex sexual behaviour in non-human mammals.

Phylogenetic distribution of the presence of same-sex sexual behaviour in males and females in the subset III (see methods). The state of the mammalian ancestral nodes was assessed using maximum likelihood estimation (black: same-sex sexual behaviour displayed by females; yellow: same-sex sexual behaviour displayed by males; purple: same-sex sexual behaviour displayed by both sexes). The silhouettes of representative mammals (downloaded from

www.phylopic.org

) illustrate the main mammalian clades. They have a Public Domain license without copyright (

http://creativecommons.org/licenses/by/3.0

).

Fig. 2

Fig. 2. Same-sex sexual behaviour from mammalian root to Hominidae.

Boxplots showing the likelihood estimation across 100 phylogenetic trees of the states of the most common recent ancestors (mrca) of the clades giving rise to the lineages of Hominidae (centre line, median; box limits, upper and lower quartiles; whiskers, minimum and maximum values). We used for the analysis the subset III. Red: significant probability (p < 0.05), according to a one-sided z-score test, of the ancestor displaying same-sex sexual behaviour; Orange: marginally significant probability of the ancestor of displaying same-sex sexual behaviour; Blue: significant probability of the ancestor of not displaying same-sex sexual behaviour; Grey: state of the ancestor was equivocal. For exact _p_-value see Table S8. The silhouettes illustrate the ancestors (downloaded from

www.phylopic.org

). They have a Public Domain license without copyright (

http://creativecommons.org/licenses/by/3.0

).

Fig. 3

Fig. 3. Factors affecting evolution of same-sex sexual behaviour.

Proportion of species displaying same-sex sexual behaviour in social vs. non-social species and in adulticidal vs. non-adulticidal species. We used for the analysis the subset III. Sample size (total number of mammal species included in each group) is shown.

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