The team tested 137 purebred dogs representing 49 breeds across two classic ethological paradigms: the so-called unsolvable task and an indoor separation test. In the unsolvable task, a dog is presented with a container holding food that it cannot open. After a brief period of solvable trials, the apparatus is secretly locked, and researchers record how the dog responds. Does it persist alone, or does it turn to the nearest human, alternating its gaze between the person and the apparatus in what ethologists call the two-stage gaze alternation? This looking-back response is widely interpreted as a solicitation of human help, a hallmark of the dog’s uniquely human-directed social attention. The separation test, meanwhile, measures how a dog copes when its owner steps out of sight, capturing behaviors such as whining, barking, and physical agitation that are associated with fear, frustration, and in extreme cases, separation-related disorder.

The first factor the researchers examined was functional selection, the historical division of breeds into those developed for cooperative work with humans, such as herding and sledding dogs, and those bred for independent work, such as livestock guarding and hunting breeds that must make decisions far from human direction. The logic of this division is straightforward: a sheepdog must constantly coordinate with its handler, while a guard dog left alone with a flock cannot afford to keep checking in with people. Decades of selective breeding for these contrasting working styles were expected to leave a measurable imprint on social cognition. The new data confirmed that expectation. Cooperative breeds displayed significantly more human-dependent behaviors in the unsolvable task than independent breeds did, turning more readily to people when the puzzle became impossible.

Yet the study’s most striking insight came from its second factor: the division within breeds. Modern pedigree breeding has split many breeds into working lines and show lines, sometimes for more than a century. Working-line dogs are still selected for performance in their original functional roles, while show-line dogs are selected primarily for conformation to breed standards and success in the ring. The researchers found that this within-breed division had a strong modifying effect on human-dependency. Working-line dogs showed weaker human-dependency than their show-line counterparts, a result that may seem counterintuitive at first glance, since working dogs are precisely the ones trained to collaborate with people. But the authors interpret this pattern through the lens of task independence: dogs bred for demanding practical work are expected to solve problems on their own and only then recruit human assistance, whereas show-line dogs, whose daily lives revolve around close handling, grooming, and constant human management, may have experienced intensified selection or simply accumulated experience favoring persistent human orientation.

The third factor moved the analysis from the breeding kennel to the dog’s own biography: regular engagement in dog sports. Whether a dog participated in activities such as agility, obedience, or other structured training turned out to be far more than a footnote. Sports engagement could actually mask the influence of the breeding lines, reshaping dependency in opposite directions depending on the dog’s genetic background. Among show-line dogs, participation in sports was associated with lower human-dependency, plausibly because these dogs learned to work through challenges with a handler’s guidance rather than defaulting to helpless solicitation. Among working-line dogs, however, sports involvement came with increased reliance on humans. The authors suggest that intensive shared training may amplify the cooperative tendencies already latent in these breeds, teaching dogs that human attention is a highly effective problem-solving resource.

The separation test added a second, emotionally charged dimension to the picture. Here, all three factors were associated with the dogs’ reactions, but the specific behaviors told different stories. Whining, which the researchers interpret as a sign of fear, was more prevalent in show-line dogs, hinting that these animals may be more vulnerable to distress when their ever-present human caretakers disappear. Barking, by contrast, was classified as a sign of frustration, and it was high in two very different groups: sport-involved dogs from independent breeds and dogs from non-working cooperative breeds. This dissociation between fear-related and frustration-related vocalizations underscores a point that behaviorists have long emphasized but the public often overlooks: separation responses are not a single phenomenon. A dog that whines and paces may be experiencing something quite different from a dog that barks insistently at the door, and the underlying causes may trace back to entirely different combinations of breeding and experience.

Taken together, the results support a conclusion that is both elegant and consequential: human-dependency is a universal trait of domestic dogs, but it is primarily determined at two levels of selection, the ancient functional selection that created breeds, and the more recent selection that carved those breeds into working and show lines. On top of this genetic architecture, lifetime experiences such as training and sports activity act as powerful modulators, capable of amplifying or dampening the inherited predisposition. In statistical terms, the study treated these factors in combination rather than in isolation, and it is precisely this multilevel design that allows the authors to disentangle effects that single-factor studies would inevitably confound. A show-line border collie that never does agility is not behaviorally equivalent to a working-line border collie that competes every weekend, even though both carry the same breed name on their papers.

The methodological care behind these findings deserves attention. The testing protocols were reviewed and approved by the Institutional Animal Welfare Committee at Eötvös Loránd University, in accordance with Hungarian regulations on animal experimentation and the guidelines of the Association for the Study of Animal Behavior. Owners were informed of the study’s aims and procedures and could halt testing at any time if they felt their dog was experiencing unacceptable stress. The dogs were recruited voluntarily through social media advertisements, and the sample’s breadth, 137 dogs spanning 49 breeds, gives the analysis genuine reach across the canine pedigree landscape, even though the authors acknowledge that breed-level and line-level conclusions rest on the distribution of dogs within their sample.

The practical implications ripple outward well beyond academic ethology. For working-dog programs, the results suggest that selecting breeding stock on pedigree lines alone may not predict the social profile of the resulting puppies; the rearing and training environment can shift the behavioral outcome substantially. For the growing field of animal-assisted interventions, where a dog’s tolerance for close human contact and its resilience during separations are critical, the finding that show-line dogs whine more when left alone could inform how therapy and assistance dogs are sourced and prepared. And for the millions of ordinary owners struggling with dogs that panic at the door, the study offers a reframing: separation distress is not a moral failing or a simple matter of spoiling, but the product of deep evolutionary currents interacting with the specific life a dog has led.

There is also a broader scientific lesson here about how we study domestication. Dogs are often described as the oldest domestic animal and a model for understanding the evolution of social cognition, yet much of the classic research treats breed as a monolithic category. This study demonstrates that the breed label conceals at least two nested layers of selection, and that an individual dog’s history of structured activity can override or redirect what those layers predict. The human-dependent behavior that makes dogs so extraordinary among animals, their willingness to gaze into our eyes and solicit our help when the world becomes unsolvable, is not written in a single set of genes. It is written in the accumulated choices of breeders across centuries, in the split between the show ring and the working field, and in the hours a particular dog spends learning, alongside a human partner, that two minds are better than one.

Subject of Research: Multilevel evolutionary and environmental influences on human-dependent behavior in domestic dogs

Article Title: The human-dependent behavior of dogs is influenced by multilevel evolutionary and environmental factors

Article References: Lugosi, C. A., Molnár, I. V., & Pongrácz, P. (2026). The human-dependent behavior of dogs is influenced by multilevel evolutionary and environmental factors. BMC Biology. https://doi.org/10.1186/s12915-026-02728-y

Image Credits: AI Generated

DOI: 10.1186/s12915-026-02728-y

Keywords: dogs, animal cognition, ethology, functional selection, breeding lines, unsolvable task, separation test, dog sports, human-dependency, domestication, cooperative breeds, behavioral genetics

The male choice hypothesis, developed by Apostolou and colleagues in a series of papers beginning in 2017, proposes that female same-sex attraction persists in populations because men find some degree of same-sex attraction in women appealing, and because such women may be more willing to engage in same-sex behavior that satisfies male partners. In this framework, male preference functions as a selective force: if men preferentially choose women with certain patterns of sexual flexibility, and if this preference translates into higher mating success or relationship stability for those women, then genes and developmental pathways associated with female same-sex attraction could be maintained by positive selection rather than eliminated by its reproductive costs. The hypothesis sits within a broader program of research by Apostolou on sexual selection under parental choice, which argues that for much of human evolutionary history parents, rather than prospective mates themselves, exercised substantial control over mating decisions.

Wilczkowski’s 2026 target article, titled Male choice hypothesis: Shortcomings, inconsistencies, and proposed alternatives, argued that the evidential foundations of this account are weaker than its proponents suggest. According to the structure of the debate, the critique pressed on multiple fronts: that the survey findings showing male approval of female same-sex attraction are modest in magnitude and vulnerable to methodological artifacts; that male preference in a modern, largely WEIRD sample does not establish an ancestral selective pressure; and that the hypothesis sits awkwardly alongside the substantial body of evidence indicating that exclusive or predominant female homosexuality is associated with reduced reproductive output. When a trait demonstrably lowers the number of offspring produced, the argument goes, a preference-based benefit must be strong and consistent enough to offset that cost, something Wilczkowski contended the existing data do not demonstrate.

Apostolou’s response takes up that challenge by reassembling the evidence base and contesting the interpretation of several key datasets. A central empirical pillar of the male choice program is work using nationally representative and convenience samples showing that a substantial proportion of men report that a partner’s same-sex attraction would not deter them, and that many men find the prospect of a female partner engaging in same-sex behavior appealing. Follow-up cross-cultural work by Apostolou and Wang extended these findings beyond Western samples, an important move because evolutionary hypotheses ultimately rest on claims about ancestral and species-wide selection pressures rather than the idiosyncrasies of contemporary college students. From this perspective, the presence of the preference across disparate cultural settings is precisely the kind of pattern one would expect if male choice had played a genuine selective role.

The reply also engages with the physiological and psychometric literature on female sexual response. Studies of sexual arousal, including work by Chivers and colleagues and more recent research on genital and subjective arousal patterns, have repeatedly found that women’s arousal is less category-specific than men’s, responding to a broader range of sexual stimuli. For proponents of male choice, this nonspecificity is consistent with a capacity for sexual fluidity that male preference could have shaped. Apostolou’s broader account of female same-sex attraction as relatively fluid, weakly canalized, and responsive to social context draws on behavioral-genetic findings from twin studies in Sweden and elsewhere, which indicate modest heritability for same-sex sexual behavior alongside substantial environmental influence, and on longitudinal cohort research showing that women’s sexual identity and attraction shift over time more often than men’s. The massive genome-wide association study published in Science in 2019 reinforced the picture of a highly polygenic, non-deterministic architecture for same-sex sexual behavior, leaving room for accounts in which developmental plasticity interacts with social selection.

Against this, the critique and the reply must both confront the reproductive cost data directly. Apostolou’s own 2022 analysis of two nationally representative U.S. samples documented a direct reproductive cost associated with same-sex attraction, meaning that women reporting such attraction had fewer children on average. This is a crucial technical point in the dispute: the male choice hypothesis does not deny the cost, it argues that the cost was historically offset by fitness benefits flowing from male preference, such as greater access to mates, improved partner retention, or cooperative alliances with other women that enhanced survival and resource acquisition. Evaluating this balancing act requires reconstructing ancestral mating markets, and it is here that the parental choice framework does much of the work. If parents historically controlled whom daughters married, as evidence from historical societies and hunter-gatherer marriage practices suggests, then women’s own preferences were under weaker sexual selection, and traits that made a woman more acceptable to the men who influenced mating decisions could plausibly spread.

Methodological disagreements run through the exchange as well. The response addresses concerns about survey design, including the treatment of midpoint responses on Likert scales, an issue with a technical literature of its own, and about the gap between stated preferences and actual mating behavior. Critics of preference-based selection arguments note that what men say they find appealing in hypothetical scenarios may bear little relation to the mate choices they make, and that self-reported attraction measures diverge to a degree from genital measures of arousal, as meta-analytic work by Chivers and colleagues has shown. Defenders counter that preference measures, when replicated across cultures and supplemented by behavioral proxies such as pornography consumption patterns and reported willingness to satisfy partners, collectively point in the same direction, and that the absence of any single perfect measure is not grounds for discarding convergent evidence. The dispute thus becomes a case study in how evolutionary behavioral scientists adjudicate between competing bodies of imperfect evidence.

The stakes of the debate extend beyond a single hypothesis. Any account of female same-sex attraction must square three robust empirical regularities: the trait is partially heritable but not strongly genetically determined; it is more fluid and less category-specific in women than in men; and predominant homosexuality carries measurable reproductive costs. The male choice hypothesis is one of several positive-selection proposals in the literature, alongside Kanazawa’s arguments about female sexual fluidity arising from generalized arousal mechanisms and Diamond’s work situating same-gender sexuality within a broader framework of fluidity and diverse forms of sexual diversity. Alternative accounts, including weak negative selection, where mildly deleterious variants persist because selection against them is too weak to eliminate them quickly, and byproduct explanations, in which same-sex attraction emerges as a side effect of selection acting on other traits, remain live competitors, and Wilczkowski’s article is explicitly framed as proposing alternatives to male choice rather than merely attacking it.

What the exchange ultimately illustrates is the current state of evolutionary hypotheses about human sexuality: rich in explanatory ambition, but constrained by the difficulty of testing claims about ancestral selection with modern data. Apostolou’s letter argues that the accumulated evidence, from male preference surveys across cultures, from the psychophysiology of female arousal, from behavioral genetics, and from anthropological records of parental control over mating, does not come close to refuting the male choice hypothesis, and that rejecting it requires a higher standard of disproof than Wilczkowski applies. Whether the hypothesis survives this scrutiny will depend on future work that can quantify how large a preference-based fitness benefit would need to be, measure male preference with methods that map onto actual ancestral mate choice, and test the predicted patterns in populations and datasets not yet examined. For now, the journal’s correspondence pages have become the arena where one of the more provocative ideas in evolutionary psychology is being stress-tested in public, and readers of sexual science are witnessing how a contested hypothesis earns, or loses, its place in the literature one rebuttal at a time.

Subject of Research: Evolutionary explanations of female same-sex attraction and the male choice hypothesis debate

Article Title: Does the Evidence Refute the Male Choice Hypothesis? A Response to Wilczkowski (2026)

Article References: Apostolou, M. (2026). Does the Evidence Refute the Male Choice Hypothesis? A Response to Wilczkowski (2026). Archives of Sexual Behavior. https://doi.org/10.1007/s10508-026-03635-7

Image Credits: AI Generated

DOI: 10.1007/s10508-026-03635-7

Keywords: male choice hypothesis, female same-sex attraction, evolutionary psychology, sexual selection, sexual fluidity, Apostolou, Wilczkowski, Archives of Sexual Behavior, parental choice, reproductive cost, mate preference, behavioral genetics