Does "Connection" in Monkey Societies Strengthen Through Sexual Intercourse? New Research on Same-Sex Behavior

Does "Connection" in Monkey Societies Strengthen Through Sexual Intercourse? New Research on Same-Sex Behavior

1) Why Do "Useless Behaviors" Persist?

When explaining animal behavior through evolutionary theory, we tend to use survival and reproduction as the primary measures. Eating, fighting, protecting offspring, and mating are straightforward behaviors. However, in nature, there are many behaviors that make us wonder, "What benefit does this serve?" Primate same-sex behavior has long been considered a prime example of this.


Same-sex intercourse does not directly lead to an increase in offspring. If there are genetic factors related to this tendency, shouldn't they be diminished through natural selection? This is the so-called "Darwin's Paradox." Recently, however, research has emerged that approaches this question from a different angle, suggesting that there might be a reason these behaviors persist, rather than simply remaining.


2) The "Conditions" Revealed by Surveying About 500 Species

The focus of this study was an analysis that aggregated extensive existing research and observational records on primates, statistically examining the relationship between species tendencies and environmental and social conditions. The key point is that it didn't just count "presence/absence," but also considered multiple factors such as climate, resource scarcity, predation pressure, lifespan, sexual dimorphism (such as body size differences), group structure, and hierarchy strength, while also accounting for phylogeny (similarities among closely related species) to explore correlations.


As a result, same-sex behavior does not appear uniformly across all species but tends to be associated with certain conditions. Broadly speaking,

  • Resource scarcity due to dryness, etc.

  • High predation pressure

  • Large sexual dimorphism (leading to intense competition)

  • Complex societies where hierarchy and alliances matter
    The more these elements are involved, the more likely same-sex behavior is to be observed.


It's important to note that this is not a simple story of "harsh environments lead to 'distraction'." The analysis suggests that factors like environment and lifespan have an "indirect" influence, while social complexity may be "directly" linked to the emergence of same-sex behavior. In other words, harsh environments change the nature of the group, and the nature of the group changes the role of sexual behavior—such a chain is being considered.


3) Sex Is Not Just for "Procreation": A Tool for Social Functioning

Primate societies are not just about living together. Relationships—who gets along with whom, who owes whom, who has more allies—directly affect food shares, the safety of offspring, and cooperation in times of danger. Here, same-sex behavior is discussed as potentially serving the following functions.

  • Reducing Tension/Avoiding Conflict
    In hierarchical societies, minor skirmishes can lead to fatal injuries. The more mechanisms there are to "soothe" relationships without direct confrontation, the more stable the group becomes.

  • Forming/Maintaining Alliances
    Solidarity among the same sex can be an advantage in territorial disputes, power struggles within the group, and vigilance/defense against predators.

  • "Practice" or Social Learning for Young Individuals
    Sexual behavior may function not only for reproduction but also as learning for future mating and relationship building.

  • Indirectly Contributing to Reproductive Success
    Individuals with more allies are safer, rise in rank, and have more opportunities for reproduction—this roundabout path could be the key to solving the paradox.


In other words, just because "offspring are not produced immediately" does not mean it is "evolutionarily meaningless." For primates, sexual behavior can be part of a repertoire of actions that reduce social friction, increase cooperation, and ultimately lay the "foundation" for survival and reproduction.


4) To Avoid Overextending to "Human Debates"

As such research gains attention, the inevitable question arises: "So what about human homosexuality?" Researchers are often cautious, emphasizing that observations of primates cannot simply explain human sexual orientation or identity. Human sexuality is intertwined with culture, history, norms, and individual experiences, not just biology.


On the other hand, the mere fact that "diverse sexual behaviors exist in nature" cannot be entirely separated from social value judgments. Given the history of "unnatural" being used as fuel for politics and prejudice, scientific discoveries do influence societal discourse. Therefore, science must carefully separate "observational facts" from "human societal norms" and craft explanations that prevent misuse.


5) Reactions on Social Media: Praise, Learning, and the "Usual" Twists

This topic spreads easily on social media for a simple reason: it has strong "surprise" value. Primates, evolutionary theory, and sexuality are all themes that easily evoke emotions, generating reactions even in short posts.


Reactions broadly fell into the following categories:

A. Scientific Surprise/Intellectual Curiosity
Many found the perspective that "sex is not just for reproduction" and "sex as a social maintenance tool" intriguing. Those familiar with primate sociality, in particular, found it easy to accept as a "mechanism to reduce conflict."


B. Emphasis on "Natural Diversity"
Posts treating "the existence of homosexual behavior in nature" as a counterargument to prejudice also increased. However, there is a caveat here. Animal behavior is not the basis for "human rights" (rights are a social contract), but it can be material to challenge prejudiced expressions. Supporters vary in how they discuss this balance.


C. Caution Against Anthropomorphism/Concerns About Misinterpretation of Research
There is a strong warning against linking "animal behavior = human sexual orientation." This serves as a healthy brake. The research discusses "functions" and "conditions," not the inner life or identity of individuals. Confusing these can lead to sloppy discussions in both science and society.


D. Twists Toward Political/Religious/Conspiracy Theory Directions (Potential for Controversy)
On public forums, the research content itself was sometimes consumed in the context of "culture wars" rather than its substance. For example, sarcastic comments like "Who imposed 'ideology' on primates?" or jibes about reconciling it with religious teachings were exchanged as jokes, derailing the topic. Such posts, due to their high spreadability, can obscure the main thrust of the research.


E. Reactions to the "Lightness" of Media Posts
While short introductions by news accounts are easy to understand, they are often perceived as "too assertive" or "sensationalist." This leads to media criticism such as "Researchers didn't make such definitive statements" or "Don't exaggerate conclusions." In reality, much of the research points to "possibilities" and "correlations," not definitive answers.


6) Ultimately, What Does This Research Change?

What makes this research interesting is its attempt to gradually dismantle the perspective of viewing same-sex behavior as a "mystery" or "exception" and reposition it as part of "behaviors that establish society." Eating, fighting, protecting offspring, mating with the opposite sex—now "sexual behavior including same-sex behavior" is lined up alongside these. To understand primate societies, explanations lacking this aspect are insufficient, according to this approach.


This perspective also serves as a lesson when considering "the evolution of behavior" beyond just primates. Evolution does not operate solely on visible "immediate benefits." Indirect benefits, benefits from relationships, benefits supported by the group—such complex bundles of gains can sometimes preserve behaviors. What seemed like a paradox was simply "our blueprint was too simplistic." This discussion suggests that possibility.


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