Many animals exhibit social learning and behavioural traditions, but human culture exhibits unparalleled complexity and diversity, and is unambiguously cumulative in character. These similarities and differences have spawned a debate over whether animal traditions and human culture are reliant on homologous or analogous psychological processes. Human cumulative culture combines high-fidelity transmission of cultural knowledge with beneficial modifications to generate a 'ratcheting' in technological complexity, leading to the development of traits far more complex than one individual could invent alone. Claims have been made for cumulative culture in several species of animals, including chimpanzees, orangutans and New Caledonian crows, but these remain contentious. Whilst initial work on the topic of cumulative culture was largely theoretical, employing mathematical methods developed by population biologists, in recent years researchers from a wide range of disciplines, including psychology, biology, economics, biological anthropology, linguistics and archaeology, have turned their attention to the experimental investigation of cumulative culture. We review this literature, highlighting advances made in understanding the underlying processes of cumulative culture and emphasising areas of agreement and disagreement amongst investigators in separate fields.

Recent studies in several taxa have demonstrated that animal culture can evolve to become more efficient in various contexts ranging from tool use to route learning and migration. Under recent definitions, such increases in efficiency might satisfy the core criteria of cumulative cultural evolution (CCE). However, there is not yet a satisfying consensus on the precise definition of efficiency, CCE or the link between efficiency and more complex, extended forms of CCE considered uniquely human. To bring clarity to this wider discussion of CCE, we develop the concept of efficiency by (i) reviewing recent potential evidence for CCE in animals, and (ii) clarifying a useful definition of efficiency by synthesizing perspectives found within the literature, including animal studies and the wider iterated learning literature. Finally, (iii) we discuss what factors might impinge on the informational bottleneck of social transmission, and argue that this provides pressure for learnable behaviours across species. We conclude that framing CCE in terms of efficiency casts complexity in a new light, as learnable behaviours are a requirement for the evolution of complexity. Understanding how efficiency greases the ratchet of cumulative culture provides a better appreciation of how similar cultural evolution can be between taxonomically diverse species-a case for continuity across the animal kingdom. This article is part of a discussion meeting issue 'The emergence of collective knowledge and cumulative culture in animals, humans and machines'.

Abstract Cumulative culture is widely seen as a uniquely human characteristic involving distinct cognitive and behavioral performances. In searching for its origin, different factors have been suggested as crucial, based on comparative studies, and dates proposed as to when cumulative culture may have emerged in human evolution. This chapter reviews possible factors, suggesting that several are necessary, not only in the social sphere but also in the individual and environmental spheres. These interdependent factors have developed in three developmental dimensions (evolutionary-biological, ontogenetic-individual, and historical-social) in interaction with the specific environment. The interplay of basic factors and developmental dimensions shows a slow and gradual development of cumulative culture from its basis to simple and advanced donated culture. The onset of cumulative culture is concluded not to have been a single-trait event that occurred in a relatively short time but rather, the result of multifactorial and gradual processes that unfolded over millions of years.

Abstract Some aspects of human cognition and behavior appear unusual or exaggerated relative to those of other intelligent, warm-blooded, long-lived social species––including certain mammals (cetaceans, elephants, and great apes) and birds (corvids and passerines). One collection of such related features is our remarkable ability for ignoring or denying reality in the face of clear facts, a high capacity for self-deception and false beliefs, overarching optimism bias, and irrational risk-taking behavior (herein collectively called “reality denial”). Such traits should be maladaptive for reproductive success when they first appear as consistent features in individuals of any species. Meanwhile, available data suggest that self-awareness (knowledge of one’s own personhood) and basic theory of mind (ToM, also termed mind-reading, intentionality etc.) have evolved independently several times, particularly in the same kinds of species mentioned above. Despite a long-standing opportunity spanning tens of millions of years, only humans appear to have gone on to evolve an extended ToM (multilevel intentionality), a trait required for optimal expression of many other unusual cognitive attributes of our species, such as advanced linguistic communication and cumulative cooperative culture. The conventional view is that extended ToM emerged gradually in human ancestors, via stepwise positive selection of multiple traits that were each beneficial. A counterintuitive alternate possibility

body hair, and large, complex brains enabling the development of advanced technology, culture, and language. Humans are highly social beings and tend to Humans (Homo sapiens, meaning 'thinking man' or 'wise man') are the most abundant and widespread species of primates, characterized by bipedalism, minimal body hair, and large, complex brains enabling the development of advanced technology, culture, and language. Humans are highly social beings and tend to live in complex social structures composed of many cooperating and competing groups, from fa Humans (Homo sapiens, meaning 'thinking man' or 'wise man') are the most abundant and widespread species of primates, characterized by bipedalism, minimal body hair, and large, complex brains enabling the development of advanced technology, culture, and language. Humans are highly social beings and tend to live in complex social structures composed of many cooperating and competing groups, from families and kinship networks to political states. Social interactions between humans have established a wide variety of values, social norms, and rituals, which bolster human society. Curiosity and the human desire to understand and influence the environment have motivated humanity's development of science, philosophy, religion, mythology and other fields of knowledge. Humans have a large and highly developed prefrontal cortex, the region of the brain associated with higher cognition. They are intelligent beings, capable of episodic memory, flexible facial expressions, self-awareness and a theory of mind. The human mind is capable of… The human brain is the locus of "higher" order functioning such as thought, reasoning, and abstraction. These cognitive processes constitute the mind, and, along with their behavioral consequences, are studied in the field of psychology. Humans have a larger and more developed prefrontal cortex than other primates, the region of the brain associated with higher cognition. This has led humans to proclaim themselves to be more intelligent than any other known species. Objectively defining intelligence is difficult, with other animals adapting senses and excelling in areas that humans are unable to. There are some traits that, although not strictly unique, do set humans apart from other animals. Humans may be the only animals who have episodic memory and who can engage in "mental time travel". Even compared with other social animals, humans have an unusually high degree of flexibility in their facial expressions. Humans are the only animals known to cry emotional tears. Humans are one of the few animals able to self-recognize in mirror tests and there is also debate over to what extent humans are the only animals with a theory of mind.