– by Nicolas Baumard & Jean-Baptiste André

The evolutionary social sciences are grounded in the idea that evolutionary theory provides a unified framework to explain human behavior, including social norms, institutions, and cultural practices. Historically, the field emerged from the inclusive fitness revolution of the 1960s and developed into a powerful toolkit for analyzing strategic behavior. Yet over time, it has fractured into three dominant traditions—Human Behavioral Ecology (HBE), Evolutionary Psychology (EP), and Cultural Evolution (CE)—that often find themselves in tension, especially when addressing cultural phenomena.

In this article, we propose an ecological approach to culture that aims to reconcile these three traditions. Our proposal draws on their most robust insights while correcting the limitations that have led to fragmentation.

From Evolutionary Psychology, we adopt the foundational idea that humans are equipped with evolved cognitive mechanisms oriented toward adaptive goals such as survival, reproduction, social status, or cooperation. However, unlike traditional EP which emphasizes the universality and domain-specificity of these mechanisms, we emphasize their plasticity and generative nature. These mechanisms are not rigid modules but adaptive systems capable of producing flexible, context-sensitive responses—including entirely novel behaviors, institutions, and cultural artifacts—based on environmental inputs.

From Human Behavioral Ecology, we adopt the insight that adaptive strategies depend on context. Humans do not pursue fitness in a vacuum; they do so under particular ecological constraints and opportunities. As such, behavior cannot be understood apart from the ecology—broadly defined to include social, economic, and informational environments—that individuals inhabit.

From Cultural Evolution, we recognize that the human environment is not only natural, but also cultural—shaped by the accumulated actions of previous generations. Humans learn many of our behaviors by watching how others do things, whether how to forage, what tools to use, or how to achieve social status, i.e., we learn culturally. These are not “transmitted” in a genetic or replicative sense, but rather function as ecological legacies — modifications of the environment that constrain and enable future behavior, much like the trails left by elephants or the structures built by beavers shape the conditions of life for subsequent individuals. Individuals choose to adopt, build on, or ignore these cultural legacies based on the payoffs for doing so, including the social payoffs.

This perspective leads us to a key divergence from standard Cultural Evolution Theory: we see no need to posit a distinct inheritance system or an analogue of natural selection operating at the cultural level. Cultural change, in our view, does not depend on the replication and differential survival of cultural variants, but on how individuals, equipped with evolved psychological mechanisms, reuse and recombine the available cultural elements in ways that serve their current goals within a given ecology.

To take a specific image, we propose thinking of cultures as akin to forests (hence the picture!). A forest is the emergent product of countless interactions between organisms, their environment, and the phenotypic structures they (and their predecessors) build to pursue adaptive goals: trees anchoring themselves in the soil, fungi forming symbiotic networks, animals digging burrows or using tree canopies for shelter, and so forth.  Like cultures, forests persist across generations and precede the individuals living in them. They constrain and enable individual actions; vary in form and structure depending on local conditions; they exhibit historical contingency and path-dependence; result from myriad individual decisions without being reducible to any one of them; display emergent integration and functional organization; and accumulate structural and organic matter over time, which further shapes the environment and the behavior of future generations.

Yet in ecology, a forest is not treated as the output of a second inheritance system or as a group-level adaptation. Rather, it is seen as the aggregate result of individual organisms pursuing their adaptive goals—organisms whose actions transform the environment for others. This altered environment, in turn, constrains and enables new strategies in a continuous feedback loop. Likewise, cultural phenomena such as religious traditions, legal systems, or market economies may appear as autonomous forces acting on individuals. But in reality, they are the ecological residue of strategic behaviors shaped by individual adaptive goals in specific historical environments. Culture is not a transmitted substance; it is the structured context that emerges from repeated and overlapping individual actions.

This ecological approach allows us to make sense of both continuity and radical change in cultural forms. The same religious tradition, artistic style, or social institution can take on very different functions and meanings across time, not because it is faithfully transmitted, but because it is continually repurposed by individuals making strategic use of new ecological conditions. What we observe as “cultural continuity” often masks deep underlying plasticity and strategic adaptation.

By focusing on proximate cognitive mechanisms and the dynamic feedback loops between individuals and their modified environments, the ecological approach to culture offers a unified framework capable of integrating the strategic reasoning of HBE, the psychological realism of EP, and the cultural legacy emphasis of CE—while avoiding the problematic assumption of cultural replication. Culture, we argue, is not a second system of inheritance; it is the ecological residue of cumulative behavior from previous generations, to which our evolved minds respond with flexible, adaptive strategies.

In placing human agents—and their evolved interests—at the heart of cultural dynamics, the ecological approach to culture not only bridges the gap between behavioral ecology, evolutionary psychology, and cultural evolution; it also reclaims the original power of inclusive fitness theory that grounded the evolutionary study of behavior. The strength of inclusive fitness lies in its parsimony and constraint: it limits what evolution can plausibly produce and thereby yields genuine explanatory and predictive power. It treats cultural behaviors as ecological phenomena, shaped by the adaptive strategies of individuals operating in environments that include the material and informational legacies of the past. This perspective brings culture back under the umbrella of adaptationist reasoning, restoring the predictive power of evolutionary theory. It allows us to understand why some traditions persist while others vanish, why cultural change can be both rapid and conservative, and why individuals sometimes embrace cultural inputs and sometimes discard them. In doing so, it reaffirms that cultural behavior, no less than any other aspect of behavior, can be explained—not just described—by evolutionary principles, constrained by the logic of inclusive fitness.

Read the original paper (here): Baumard, N., & Jean-Baptiste André, J.-B. (2025). The ecological approach to culture. Evolution & Human Behavior, 46(3), 106686.

– by Robert Bowers

There is a large ground bird from the American plains whose mating system could not be more convenient for studying sexual selection. Over a conveniently short mating season, male sage grouse gather in a conveniently compact space, within a few miles of each other, and there they all perform their best mating displays. The hens of this species browse the performances at their leisure and choose a mate. This event attracts not only competing cocks and broody hens, but also biologists keen on showing how the striking sexual dimorphisms expressed in this species relate to female choice and intersexual sexual selection. Unsurprisingly, mating variance among male sage grouse is large, and optimism was high that with enough clipboards, the exaggerated waddles and dances and girth of these males would all have a clear explanation. But the mating variance was too great. Even with all the elaborate male characters of these birds, there were still insufficient bases to explain the extent that some hens chose the most successful males. In apparent exasperation, there is a remark in the middle of a 1960’s doctoral thesis that the females might be copying each others’ choices.

The subsequent area within sexual selection research, initially termed “female copying”, grew in several ways. Theoreticians showed its relation to reproductive variance and sexual selection. Experimentalists demonstrated it empirically in laboratory demonstrations. And phylogenetically, it grew in the breadth of species that were shown to be affected. However, even with all these advances, it remained within the theoretical context of female choice, and continued to be studied as if it were an exclusively female phenomenon. Even among humans, a species in which both sexes choose, a large majority of “mate-choice copying” (what the phenomenon is now called) studies focused exclusively on females choosing males.

Among humans, however, the earliest documented recognition of mate-choice copying (in a dating advice column from 1928, predating the sage grouse observation by decades), was actually about men copying the choices of other men. Indeed, studies that have included both men and women have most often found that both sexes are affected by the choices of others. Despite this, it remains common to find mate-choice copying presented as a specifically female phenomenon. Typically, this sentiment is accompanied with reference to Parental Investment Theory, the popular view that the sex that suffers greater costs in reproduction will have greater use for any means of choosing better mates. The received view is that women should engage in social mate choice heuristics more than men.

But mate choice is complicated, and harnessing information about mates from attending to others’ choices is no less so. When one considers mate-choice copying more closely, several features of social mate-choice information (as well as of human parental care) muddy the theoretical waters that motivate looking for a sex difference. Mate-choice information is readily accessible, relevant to both sexes, indicative of characters not visible on the surface, and fallible. Copying others’ choices heightens competition. Paternal care among humans is long and extensive. All of these features push expectations in various directions about what kind of sex difference should or should not express in how people attend to others’ choices when choosing a mate.

Not long ago, we decided to address this question directly. One problem in assessing sex difference claims from previous data was that male and female participants are typically presented with different stimuli. Male mate choice is assessed with images or videos of women, and female mate choice is assessed with images or videos of men. And one point that has been clear from the earliest human mate-choice copying studies is that the specific stimuli matter; the strength of the effect depends heavily on such features as the relative attractiveness of the stimuli employed.

To address whether the sexes differ in the extent that they rely on social mate-choice heuristics, we removed all sex-specific stimuli so that we could present the very same stimuli to male and female participants. Profiles furthermore included only accurate information about real daters making sincere choices in the context of a speed-dating event.

Our results did not support the kind of sex difference expected by the received view. We did find evidence of human mate-choice copying, but both male and female participants changed their ratings in the direction of others’ choices, and to comparable extents.

This matters because mate-choice copying is both a cause and a consequence of sexual selection. As a consequence, it being sex-general implies that there is substantial pressure on both sexes to be selective. As a cause, the sex-generality of mate-choice copying is expected to have the effect of increasing reproductive variance, and so of intensifying selection on sex-specific characters in both sexes.

These results add human mate-choice copying to the growing list of phenomena that do not abide expectations of the still dominant set of views related to Parental Investment Theory, Sexual Strategies Theory, and Bateman’s Principle. These views satisfy aesthetically but are increasingly found to falter empirically, not necessarily because they are wrong, but because mate choice is complicated, and because human mate choice and parenting are not so one-sided as in the comparatively extreme mating systems amid which these ideas were developed. The good news is that with attention to the specific features of the structure of the problem mate seekers face, there are fine grounds for refining understanding of sexual selection in the context of how copying others’ choices allows mate seekers to harness social information about mate quality.

Read the original article: Bowers, R.I., Pinar, V., Sariyildiz, S.S., & Parlak, D. (2025) Is mate-choice copying a female phenomenon? Evolution & Human Behavior, 46(1), 106653.

– By Carlota Batres

When it comes to children, women can be certain that a child is theirs, but men cannot. In other words, there is always some chance that another man fertilized the woman’s egg. The estimate of children who have genetic fathers different from their alleged fathers is between 1%-3%.

One of the sources of information that men use to determine the likelihood of being the genetic father is perceptions of the child’s physical similarity. Research has found that fathers who perceive that their children resemble them invest more in those children, for example by spending more time with them and by having more supportive/engaged parenting.

In our study, we aimed to examine whether mothers having an ultrasound would claim that the fetus looks more like the father. Even with such limited visual information, we predicted that mothers would be more likely to say that the fetus resembled the father in an effort to assure paternity.

In addition to perceptions of the child’s resemblance, men also use information about their partner’s faithfulness and trustworthiness to determine how likely they are to be the biological father. For instance, one study found that men’s perceptions of their partner’s fidelity predicted their parental investment. Marriage is one way in which couples pledged faithfulness to each other. Indeed, while infidelity takes place in married couples, the incidence of cheating is much lower than it is in unmarried couples. Therefore, for our study, we also aimed to examine differences between parents who were married and parents who were not. We predicted that among unmarried parents, mothers would be even more likely to say that the fetus resembled the father.

Participants were recruited at an obstetrics and gynecology clinic, mostly during their routine 20-week pregnancy ultrasound. If they decided to participate, they were given a questionnaire and then called in for their ultrasound. Once the fetus was visible in the 2D imaging, if the biological mother and the biological father were in the ultrasound room (as per the participants’ questionnaire responses), the ultrasound technician would ask them “Who do you each think the baby looks like?” and would record their answers.

We found that fathers were just as likely to say the fetus resembled themselves (49%) as they were to say that the fetus resembled the mother (51%). However, mothers were significantly more likely to say that the fetus resembled the father than to say that the fetus resembled themselves. In fact, 26% said that the fetus resembled themselves and 74% said that the fetus resembled the father. Moreover, mothers who were not married were even more likely to say that the fetus resembled the father than married mothers. More specifically, 93% of unmarried women said that the fetus resembled the father.

Evidence from our study supports the hypothesis that mothers should be more likely to say that the fetus resembles the father. If the fetuses actually did resemble the fathers, the fathers should also be more likely to say that the fetuses look like them. However, we did not find this to be the case. Rather, we only saw this effect with mothers, suggesting that the unconscious bias in mothers’ observations about similarity to the fathers does not reflect actual resemblance. This is supported by other research which has found that when unrelated participants were asked to match photographs of parents to newborns, they were more accurate in matching the mothers than the fathers.

In conclusion, our study provides evidence that even with extremely limited visual information, mothers have a bias toward claiming paternal similarity. This bias is likely an adaptation that helps the mothers secure investment in their unborn children since fathers who believe that their children resemble them invest more in those children.

Read the original article: Batres, C., Mullen, A., Krofl, S., & Trainor, L. (2025). Investigating perceptions of fetal resemblance. Evolution and Human Behavior, 46(2), 106670.