The field of evolutionary social sciences is founded on the principle that evolutionary biology provides valuable tools for understanding and explaining social phenomena in humans. While this framework has traditionally been applied to biological traits and behaviors, culture was long considered outside the purview of evolutionary explanations, often seen as too complex or dynamic to be analyzed within the same framework. However, the past decades have witnessed a transformative shift with the emergence and growth of cultural evolution as a scientific field withing evolutionary sciences (Barrett, 2014; Boyd & Richerson, 1985; Boyer, 2018; Brown, Dickins, Sear, & Laland, 2011; Claidière, Scott-Phillips, & Sperber, 2014; Henrich, 2015; Mesoudi, Whiten, & Laland, 2006; Nettle, 2009; Tooby & Cosmides, 1992). This integration has allowed researchers to examine cultural phenomena such as religion, technology, and social norms not as an anomaly but as an extension of evolutionary processes.

So far, the field of cultural evolution has mostly conceptualized cultural phenomena as a second system of inheritance, analogous to (and in many ways different from) genetic inheritance (Boyd & Richerson, 1985; Brown et al., 2011; Campbell, 1965; Cavalli-Sforza & Feldman, 1981; Dawkins, 1976; Henrich, 2015; Laland & Brown, 2011; Lumsden & Wilson, 2005; Mesoudi et al., 2006). Behaviors, practices, and ideas are transmitted across generations through processes such as observation, imitation, teaching, and other forms of social learning. This replicatory dynamic gives rise to a substantially autonomous process of cultural selection that explains the features of cultural phenomena such as their persistence, their creativity and their functionality.

While this approach, often called Dual Inheritance Theory (DIT), has been pivotal in integrating cultural phenomena into evolutionary science, it increasingly relies on concepts and theories that diverge from those of standard evolutionary biology (Claidière et al., 2014; Claidière & André, 2012; Cronk, 1995; Daly, 1982; Micheletti, Brandl, and Mace, 2022; Micheletti, Brandl, Zhang, Peacey, & Mace, 2023; Nettle, 2020; T. C. Scott-Phillips, Dickins, & West, 2011, 2011, 2014; Tooby & Cosmides, 1990; West, El Mouden, & Gardner, 2011). Many proponents of DIT have even called for an ‘extended evolutionary synthesis’ moving away from the core principles of inclusive fitness theory (Laland et al., 2015).

We believe this is an unnecessarily high cost to pay for the study of culture. Evolutionary biology offers a powerful way of thinking which compels researchers to explain phenomena using a concise set of mechanisms rooted in inclusive fitness theory (Williams, 1996). Here, we argue that we don't need to pay such a cost. We propose an alternative approach to cultural phenomena that eliminates the need for a separate system of inheritance or distinct principles. Instead, we argue that the same evolutionary framework that explains biological traits can also account for cultural phenomena effectively and cohesively.

Our approach begins with the observation that while cultural phenomena are often defined by their persistence and continuity across generations, they are equally marked by innovation and change. In some cases, individual behaviors display little variations across generations, yet in others, each generation diverges significantly from the one before, and these behaviors are primarily driven by individual adaptive goals. What defines cultural phenomena is not merely their persistence and continuity, but the broader dynamic in which the behaviors of earlier generations leave a lasting impact on the behaviors of subsequent generations. This intergenerational influence creates both continuity and change.

While this intergenerational influence is often seen as unique to culture, it is not. All organisms modify their environment—a process known as ‘ecosystem engineering’ (Hastings et al., 2007a; Jones, Lawton, & Shachak, 1994). Examples include: beavers building dams; earthworms aerating soil; coral reefs forming underwater structures used by other species; elephants modifying savanna landscapes by uprooting trees; prairie dogs digging burrow systems that will be reused by other species; kelp altering underwater currents and light availability; fungi decomposing organic matter and changing soil composition; mangroves shaping coastal landforms and sedimentation patterns; and many other phenomena. These environmental modifications persist creating ‘ecological legacies’ that affect subsequent generations (Cuddington, 2011; Frauendorf et al., 2021; Hastings et al., 2007; Jordan, Larson, & Huerd, 2011; Nuttle, Yerger, Stoleson, & Ristau, 2011; D. A. Perry, Oren, & Hart, 2008). Organisms then adapt plastically to these altered conditions, —a process often called ‘ecological response’ (Sheridan & Bickford, 2011; M. G. Turner et al., 2003). This, in turn, may create ‘ecological cascades’. For instance, beaver dams modify water flow, sedimentation, and nutrient distribution in streams (Carpenter, Kitchell, & Hodgson, 1985; Estes & Palmisano, 1974; Ripple & Beschta, 2012). Altered water flow then creates wetlands, to which some species respond well (e.g., waterfowl). These changes ripple through trophic levels, influencing predators, prey, and even surrounding terrestrial systems.

Importantly, not all responses to ecological modifications are genetic adaptations; many are phenotypic adjustments driven by adaptive plasticity. When an organism encounters a modified environment—whether due to beaver dam construction or changes in vegetation—it can often adjust its physiology, behavior, or developmental trajectory to cope with these new conditions without requiring genetic change. Many non-human animals plastically modulate their behaviors to exploit the novel ecological niches created by human-induced rapid environmental change (Sih, 2013; Sol, Bacher, Reader, & Lefebvre, 2008; Tuomainen & Candolin, 2011; Wright, Eberhard, Hobson, Avery, & Russello, 2010). For instance, raccoons have learned to open garbage cans, forage in dumpsters, and navigate human structures to find food.

These ecological processes are not limited to between species interactions. They also occur within individuals of the same species, just like cultural phenomena. For example, bowerbirds reuse materials like colorful stones from bowers built by other bowerbirds (Madden, 2008). Similarly, new termite colonies often occupy mounds left by their predecessors (Laidre, 2021a, Laidre, 2021b). Lemon ants inhabit “devil's gardens” in the Amazonian rainforest—monocultures of certain tree species that they have engineered and maintained over multiple generations, often persisting for centuries (Frederickson, Greene, & Gordon, 2005). Moreover, these legacies impact the behaviors of subsequent generations. For instance, the architectural decision of one generation of bees (helicoidal or flat stacked combs) can constrain the architectural decisions of subsequent generations, leading to some architectural traditions (Di Pietro et al., 2024). Similarly, terrestrial hermit crabs architecturally remodel shells. These modified shelters are reused by subsequent generations long after the original architect's death, and their presence or absence alter the life history of the populations (Laidre, 2019).

In these examples, the behavior of past generations affects the behavior of younger generations through ecological modifications and phenotypic ecological responses. Our point is that human cultures are no different. Humans constantly produce ecological modifications to fulfill their own adaptive goals: roads, houses, tools, jokes, words, novels, songs, religious beliefs (Fig. 1). These cultural artifacts change the material, social, and informational ecology of others, altering the conditions in which future generations survive and develop. In response, new generations plastically respond to these modified environments, using them to pursue their own adaptive goals. Over time, these interactions generate cascading effects, mirroring ecological cascades observed in non-human ecosystems.

Importantly for the purpose of explaining cultural phenomena, individuals usually do not aim at replicating or imitating the ecological legacies that they find in their environments. Elephants do not try to imitate or replicate existing paths. They are just using what is most useful in their environment to achieve their adaptive goals (e.g. moving from one point to another in the most efficient way). Because elephants are behaviorally flexible, they have the option of ignoring existing paths (Gómez et al., 2023; Pfennig et al., 2010). If they choose to use these paths, it's because they have advantages: they're optimally laid out, and they've been maintained (branches spread apart, etc.). But individuals can nonetheless choose other paths or transform old paths (Blake & Inkamba-Nkulu, 2004; Shepard et al., 2013). Similarly, hermit crabs do not have to imitate others and use the shells they left in the environment. On the contrary, each individual crab chooses whether or not to use the shells produced by other individuals (Laidre, 2019).

The consequence of this ecological process is that individuals are most often do not benefit from faithfully imitating others. They are interested in acquiring food, helping their family, attracting cooperation partners, gaining status, manipulating others, avoiding pathogens, signaling their mate-value; and they can recycle, tweak, and selectively retain part of the phenotypic legacies of other individuals to fulfill these adaptive goals. The result of this process is a constant mix of re-cycling, up-cycling, down-cycling, innovation and accumulation of ecosystem modifications from one individual to the next. In other words, ecological processes do not constitute a system of inheritance (sensu DIT).

Similarly, humans are not passive recipients of ecological modifications. They actively engage with, modify, and adapt to the cultural contexts they inhabit (Gweon, 2021; Micheletti et al., 2023; Morin, 2016; T. C. Scott-Phillips, 2022; Sperber, 1996; Sterelny, 2024; Sterelny & Hiscock, 2024). For instance, individuals innovate tools, reinterpret traditions, or negotiate social norms to suit their goals or solve local problems. Yet, sometimes, individuals preserve or recreate the legacies produced by past generations because, in some cases, such as communication systems (e.g. languages) or conventions (e.g. driving on the right), what is best for one generation is also best for a later one. As a result, individuals end up using the same items as earlier individuals—leading to what could be conceptualized as an inheritance process. But most of the time, humans do not use exactly the same items, leading to cultural change (Claidière et al., 2018; Garland & McGregor, 2020; Karjus, Blythe, Kirby, & Smith, 2020; Kirby, Cornish, & Smith, 2008, Kirby, Cornish, and Smith, 2008; Osiurak et al., 2022; Zwirner & Thornton, 2015). Words are abandoned, syntax changes, fashions fade, technologies are replaced, novels are no longer read, cooler music emerges (Morin, 2016). A classic novel that was once a source of pleasurable entertainment is now used by the new generations as an instrument of social signaling (Bourdieu, 1984; Goffman, 1956). In essence, culture encompasses the ecological modifications individuals produce, their effects on others, and the adaptive responses they trigger.

Ecological processes do not instantly produce the rich diversity and complexity of cultural phenomena we observe today, as well as the key features that interest cultural evolution scientists such as tradition, innovation, cumulativity (Boyd & Richerson, 1985; Henrich, 2015; Mesoudi et al., 2006). Instead, these phenomena unfold over many cycles of ecological modifications, ecological legacies and ecological responses. It is the repetition of these cycles that eventually gives rise to cultural evolution.

The view developed here naturally converges with the adaptive perspective of human behavioral ecology and evolutionary psychology (André, Baumard, & Boyer, 2023; M. Borgerhoff Mulder, 1991; Boyer, 2018; Cronk, Chagnon, & Irons, 2000; Micheletti et al., 2023; Nettle, 2009; Tooby & Cosmides, 1992). In essence, the ecological approach to culture continues the inclusive fitness revolution. The inclusive fitness revolution has been about understanding biological phenomena from the point of view of the genes (Ågren, 2021; Dawkins, 1976; Hamilton, 1964; Rodrigues & Gardner, 2022; Trivers, 1971, Trivers, 1974; Wilson, 1975). Over the past 50 years, inclusive fitness reasoning been successfully applied to all kinds of phenotypic traits: organs, brains, diseases, sexuality, parenting, eusociality, cooperation. It has expanded from physiological traits (i.e., evolutionary biology) to behavioral traits (i.e., behavioral ecology) to psychological mechanisms (i.e., evolutionary psychology). In this paper, we propose to further expand the inclusive fitness framework to cultural products (i.e. cultural evolution).

The paper is structured as follows. In Section 2, we establish the parallels between cultural and ecological processes, demonstrating that key cultural features—such as persistence, innovation, and cumulative change—arise from standard ecological mechanisms rather than a distinct system of inheritance. This section also examines how cultural dynamics operate through the same fundamental principles as other ecosystems, highlighting the role of ecological modifications, phenotypic responses, and ecological cascades in shaping cultural evolution. Section 3 bridges the gap between inclusive fitness theory and culture, explaining how cultural phenomena emerge from individuals pursuing adaptive goals in response to environmental modifications, without requiring a separate transmission system. Section 4 discusses the broader implications of this ecological approach, emphasizing the immense benefits of reclaiming inclusive fitness theory for the study of cultural evolution. Finally, in Section 5, we examine the implications of this framework for defining culture itself, proposing a revised definition that integrates cultural phenomena within the broader framework of ecology and evolution.