Spreading rumors or intentionally excluding a peer from a social group is often considered undesirable behavior. New research suggests that this type of covert hostility is associated with being more likely to be in a romantic relationship and have more children. The study, published in the journal Evolutionary Psychological Science, shows that subtle forms of aggression may provide a reproductive advantage in modern humans.
Evolutionary psychologists track the number of children people have to measure evolutionary fitness. This indicator reflects how well an individual passes on his or her genetic material to the next generation. If a particular inherited trait produces more offspring, its underlying genetics become more common in a population over time. This process is the basic mechanism of natural selection.
Researchers are studying a variety of psychological traits to see if they are actively shaped by modern natural selection. Traits such as extraversion and neuroticism have already been shown to be associated with reproductive outcomes. Evolutionists have proposed that aggressive behavior may also be an adaptive trait. Aggression helps individuals defend territory, secure limited resources, and compete for mating opportunities.
Human aggression can be divided into two broad categories depending on how it is expressed. Direct aggression includes overt physical or verbal aggression, such as hitting or yelling. Indirect attacks rely on covert tactics to inflict harm. A particular type of indirect aggression, known as relational aggression, focuses on damaging the victim’s social status and interpersonal relationships.
Relational aggression includes gossiping, withholding friendships, and manipulating others to isolate rivals. From an evolutionary perspective, direct physical attacks carry high risks. Those who are overtly aggressive may suffer physical injury, face social ostracism, or face legal penalties. Relational aggression maximizes harm to the victim while keeping the aggressor relatively safe from physical retaliation and direct blame.
Previous research has struggled to directly link aggression to actual reproductive success in modern humans. Evolutionary studies have often relied on reproductive indicators, such as number of mates and age at first sexual experience. When data on actual fertility were available, researchers frequently used biological proxies for aggression, such as upper body strength.
Marcin Molon, a researcher at the Institute of Psychology at the University of Silesia in Poland, designed a study to test whether relational aggression has quantifiable reproductive benefits in modern societies. His research aimed to test the evolutionary adaptability of covert hostility by focusing on actual fertility rather than surrogate dating.
Moron analyzed data from 1,497 Polish adults who participated through an online survey platform. Participants ranged in age from 18 to 81 years, with a mean age of approximately 48 years. Just over half of the respondents were women. Participants completed a demographic survey asking about their socioeconomic status, relationship status, and number of biological children.
Participants also completed a series of questions assessing their disposition toward relational aggression. The study divided these hostile behaviors into two different categories. One category measured aggression directed toward peers, asking whether participants tried to embarrass someone or threatened to withdraw a friendship to get their way. The other category measured aggression directed toward a romantic partner, such as intentionally trying to make a spouse jealous.
Moron used a statistical model called Poisson regression to examine the relationship between these aggressive tendencies and the participants’ reported number of children. These statistical models are specifically designed to analyze numerical data such as number of offspring. The model took into account demographic variables such as age, gender, socio-economic status, and whether the respondent was currently in a romantic relationship.
Those who reported higher levels of relational aggression from peers were found to be more frequently involved in romantic relationships than those with lower levels. After controlling for age and socio-economic factors, higher levels of peer aggression were found to be associated with higher number of biological children. The data showed a positive association between covert peer aggression and fertility for both men and women.
The study then isolated participants who were currently in a romantic relationship. Within this particular group, higher levels of relational aggression directed toward romantic partners were also associated with having more children. Looking at simple statistical correlations, this particular association appeared primarily among men.
Formal regression models assessing all overlapping variables simultaneously did not identify any clear differences between men and women in this regard. In the final model, the interaction between gender and relational aggression was not statistically significant. Moron noted that these sex differences are not clear-cut, so the proposed explanations for these behaviors may apply equally to men and women.
Relational aggression may serve as an evolutionary strategy to compete with members of the same sex. Lowering your romantic rival’s social status increases your chances of attracting a desirable partner. This strategy is known in evolutionary biology as rival neglect. If these strategies improve mating success, they may ultimately be able to produce more offspring over their lifetime.
Within established relationships, relational aggression can function as a tactic to maintain a spouse. Behaviors aimed at manipulating partners or deterring external rivals can stabilize long-term relationships and generally predict increased fertility. Alternatively, this aggressive behavior may push your partner away. This may cause the aggressive person to break up, find a new partner, and have children in multiple relationships.
The study results were based on a cross-sectional design, meaning that data were collected at a single point in time. This type of observational data prevents researchers from determining simple cause and effect. Being in a relationship may initially make you more interpersonally aggressive as you try to protect your partner, rather than aggression leading to romantic success.
The study also relied on self-report questionnaires. People may underestimate or underreport how often they use manipulative tactics because they want to appear favorable to researchers. Future research could use reports from peers and partners to more objectively measure a person’s aggressive tendencies.
The observed effects of relational aggression on fertility were relatively small in magnitude. Factors such as a person’s age and relationship status played a much larger role in predicting the number of children. The study also lacked data on variables such as voluntary childlessness and contraceptive use. Tracking these factors reveals exactly how aggressive individuals navigate modern family planning.
Future research should examine these social dynamics over continuous time scales rather than single snapshots. Longitudinal studies can follow individuals from adolescence to reproductive age to see how aggressive strategies change over time. Despite the limitations, the current findings suggest that subtle covert aggression may continue to play a role in human reproductive success.
The study, “Relational Aggression and Lifelong Offspring: A Preliminary Study in a Large Community-Based Sample of Polish Adults,” was authored by Marcin Moron.
