3.3 million years of stone tool complexity suggests that cumulative culture began during the Middle Pleistocene

Cumulative culture, the accumulation of modifications, innovations, and improvements over generations through social learning, is a key determinant of the behavioral diversity across Homo sapiens populations and their ability to adapt to varied ecological habitats. Generations of improvements, modifications, and lucky errors allow humans to use technologies and know-how well beyond what a single naive individual could invent independently within their lifetime. The human dependence on cumulative culture may have shaped the evolution of biological and behavioral traits in the hominin lineage, including brain size, body size, life history, sociality, subsistence, and ecological niche expansion. Yet, we do not know when, in the human career, our ancestors began to depend on cumulative culture. Here, we show that hominins likely relied on a derived form of cumulative culture by at least ~600 kya, a result in line with a growing body of existing evidence. We analyzed the complexity of stone tool manufacturing sequences over the last 3.3 My of the archaeological record. We then compare these to the achievable complexity without cumulative culture, which we estimate using nonhuman primate technologies and stone tool manufacturing experiments. We find that archaeological technologies become significantly more complex than expected in the absence of cumulative culture only after ~600 kya.

Organic geochemical evidence of human-controlled fires at Acheulean site of Valdocarros II (Spain, 245 kya)

Among the outstanding questions about the emergence of human-controlled fire is the systematic recurrence between the geochemical remains of fire and its preservation in the archaeological record, as the use of fire is considered a technological landmark, especially for its importance in food cooking, defensive strategies, and heating. Here we report fossil lipid biomarkers associated with incomplete combustion of organic matter at the Valdocarros II site, one of the largest European Acheulean sites in Spain dated to marine isotopic stage (MIS) 8/7 (~ 245 kya) allowing a multiproxy analysis of human-controlled fire use. Our results reveal isolated cases of highly concentrated and diverse polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs (APAHs), along with diagnostic conifer-derived triterpenoids in two hearth-like archaeological structures. The presence of combustion byproducts suggests the presence of anthropogenic (controlled) fires at Valdocarros-one of the oldest evidence of fire use in Europe-in association with Acheulean tools and bones. Hominins possibly used fire for two main activities, as a means of defense against predators and cooking. Our results help to better delineate major gaps in our current knowledge of human-controlled fire in the context of the Middle-Pleistocene in Europe and suggest that human ancestors were able to control fire before at least 250 kya.

Middle Pleistocene fire use: The first signal of widespread cultural diffusion in human evolution

Control of fire is one of the most important technological innovations within the evolution of humankind. The archaeological signal of fire use becomes very visible from around 400,000 y ago onward. Interestingly, this occurs at a geologically similar time over major parts of the Old World, in Africa, as well as in western Eurasia, and in different subpopulations of the wider hominin metapopulation. We interpret this spatiotemporal pattern as the result of cultural diffusion, and as representing the earliest clear-cut case of widespread cultural change resulting from diffusion in human evolution. This fire-use pattern is followed slightly later by a similar spatiotemporal distribution of Levallois technology, at the beginning of the African Middle Stone Age and the western Eurasian Middle Paleolithic. These archaeological data, as well as studies of ancient genomes, lead us to hypothesize that at the latest by 400,000 y ago, hominin subpopulations encountered one another often enough and were sufficiently tolerant toward one another to transmit ideas and techniques over large regions within relatively short time periods. Furthermore, it is likely that the large-scale social networks necessary to transmit complicated skills were also in place. Most importantly, this suggests a form of cultural behavior significantly more similar to that of extant Homo sapiens than to our great ape relatives.

A detailed analysis of the spatial distribution of Schöningen 13II-4 'Spear Horizon' faunal remains

The Middle Pleistocene Schöningen 13II-4 'Spear Horizon' (Germany) is a key site for the study of human evolution, most notably for the discovery of Paleolithic wooden weaponry and evidence for developed hunting strategies. On the other hand, the 'Spear Horizon' offers an excellent opportunity to approach hominin spatial behavior, thanks to the richness of the archeological assemblage, its exceptional preservation, and the vast expanse of the excavated surface. Analyzing how space was used is essential for understanding hominin behavior at this unique open-air site and, from a wider perspective, for approaching how humans adapted to interglacial environments. In this article, we present an exhaustive spatial study of the complete Schöningen 13II-4 'Spear Horizon' faunal assemblage and its archeological context, combining zooarcheology and spatial analysis through the extensive application of geographic information systems. Our results indicate the existence of different activity areas related to changes in the position of the shoreline due to fluctuations of water table levels of the Schöningen paleolake. These activity areas were likely used on a seasonal basis, whereas the spatial patterning observed in the distribution of faunal remains suggests a diversity of behavioral strategies in terms of intensity and/or duration of occupations. This study refines previous interpretations of the site and reconstructs human behavioral adaptations and the occupational changing lakeland environment during the Middle Pleistocene in Europe.

Evaluating social contract theory in the light of evolutionary social science

Political philosophers have long drawn explicitly or implicitly on claims about the ways in which human behaviour is shaped by interactions within society. These claims have usually been based on introspection, anecdotes or casual empiricism, but recent empirical research has informed a number of early views about human nature. We focus here on five components of such views: (1) what motivates human beings; (2) what constraints our natural and social environments impose upon us; (3) what kind of society emerges as a result; (4) what constitutes a fulfilling life; and (5) what collective solutions can improve the outcome. We examine social contract theory as developed by some early influential political philosophers (Hobbes, Locke and Rousseau), who viewed the social contract as a device to compare the 'natural' state of humans with their behaviour in society. We examine their views in the light of recent cross-cultural empirical research in the evolutionary social sciences. We conclude that social contract theorists severely underestimated human behavioural complexity in societies lacking formal institutions. Had these theorists been more informed about the structure and function of social arrangements in small-scale societies, they might have significantly altered their views about the design and enforcement of social contracts.

The challenges of documenting coevolution and niche construction: The example of domestic spaces

This essay delves into some of the challenges of studying the coevolution of humans and domestic spaces. These constructed arenas center on food preparation, and as part of the heritable niche they can shift the opportunities for, and constraints on, social interaction and cooperation in evolutionary time. Domestic spaces are widely evidenced in the archeological record, but investigators have made little progress in demonstrating causal links between proposed feedback spirals and constructed spaces of any sort. Bridging fine-scale and large-scale processes in coevolutionary systems is a complex problem that must engage higher levels of generative evolutionary theory. Archaeology nonetheless stands to offer a great deal to larger research programs by documenting and analyzing the pathways of change based on site formation processes along with evidence from subsistence refuse and technology. Choice models remain valuable tools for investigating aspects of the fine-scale feedback processes involved.

Productivity loss associated with functional disability in a contemporary small-scale subsistence population

In comparative cross-species perspective, humans experience unique physical impairments with potentially large consequences. Quantifying the burden of impairment in subsistence populations is critical for understanding selection pressures underlying strategies that minimize risk of production deficits. We examine among forager-horticulturalists whether compromised bone strength (indicated by fracture and lower bone mineral density, BMD) is associated with subsistence task cessation. We also estimate the magnitude of productivity losses associated with compromised bone strength. Fracture is associated with cessation of hunting, tree chopping, and walking long distances, but not tool manufacture. Age-specific productivity losses from hunting cessation associated with fracture and lower BMD are substantial: ~397 lost kcals/day, with expected future losses of up to 1.9 million kcals (22% of expected production). Productivity loss is thus substantial for high strength and endurance tasks. Determining the extent to which impairment obstructs productivity in contemporary subsistence populations improves our ability to infer past consequences of impairment.

A Middle Pleistocene abrading tool from Tabun Cave, Israel: A search for the roots of abrading technology in human evolution

During the reanalysis of the finds from Jelinek's and Ronen's excavations at Tabun Cave, Israel, we encountered a cobble bearing traces of mechanical alterations similar to those recorded on grinding tools. However, the artifact derives from the early layers of the Acheulo-Yabrudian complex of the late Lower Paleolithic (ca. 350 ka), a time with no evidence for grinding or abrasion. Accordingly, we sought to determine whether the traces on the artifact can be attributed to purposeful human action. We conducted a detailed use-wear analysis of the cobble and implemented an experimental program, gaining positive results for the hypothesis of purposeful human practice. We argue that the significance and novelty of early abrading technology is that it marks a new mode of raw material manipulation-one that is categorically different from other modes of tool use observed among earlier hominins or other primates and animals. Throughout the Early Pleistocene, use of stone tools was associated with vertical motions (battering, pounding, striking) or with the application of a thin or narrow working edge, leveled at cutting or scraping. Conversely, abrading consists in applying a wide working surface in a continuous sequence of horizontal motions, geared to modify or reduce the surfaces of a targeted material. The emergence of this technology joins additional behavioral changes recently identified and attributed to the Middle Pleistocene, illustrating the growing and diversifying capabilities of early hominins to harness technology to shape their environment.

Origins of music in credible signaling

Music comprises a diverse category of cognitive phenomena that likely represent both the effects of psychological adaptations that are specific to music (e.g., rhythmic entrainment) and the effects of adaptations for non-musical functions (e.g., auditory scene analysis). How did music evolve? Here, we show that prevailing views on the evolution of music - that music is a byproduct of other evolved faculties, evolved for social bonding, or evolved to signal mate quality - are incomplete or wrong. We argue instead that music evolved as a credible signal in at least two contexts: coalitional interactions and infant care. Specifically, we propose that (1) the production and reception of coordinated, entrained rhythmic displays is a co-evolved system for credibly signaling coalition strength, size, and coordination ability; and (2) the production and reception of infant-directed song is a co-evolved system for credibly signaling parental attention to secondarily altricial infants. These proposals, supported by interdisciplinary evidence, suggest that basic features of music, such as melody and rhythm, result from adaptations in the proper domain of human music. The adaptations provide a foundation for the cultural evolution of music in its actual domain, yielding the diversity of musical forms and musical behaviors found worldwide.

Paternal provisioning results from ecological change

Paternal provisioning is ubiquitous in human subsistence societies and unique among apes. How could paternal provisioning have emerged from promiscuous or polygynous mating systems that characterize other apes? An anomalous provisioning male would encounter a social dilemma: Since this investment in prospective offspring can be expropriated by other males, this investment is unlikely to increase the provisioner’s fitness. We present an ecological theory of the evolution of human paternal investment. Ecological change favoring reliance on energetically rich, difficult-to-acquire resources increases payoffs to paternal provisioning due to female–male and/or male–male complementarities. Paternal provisioning becomes a viable reproductive strategy when complementarities are strong, even under high paternity uncertainty. This model illuminates additional paths for understanding the evolution of fatherhood.

Paternal provisioning among humans is puzzling because it is rare among primates and absent in nonhuman apes and because emergent provisioning would have been subject to paternity theft. A provisioning “dad” loses fitness at the hands of nonprovisioning, mate-seeking “cads.” Recent models require exacting interplay between male provisioning and female choice to overcome this social dilemma. We instead posit that ecological change favored widespread improvements in male provisioning incentives, and we show theoretically how social obstacles to male provisioning can be overcome. Greater availability of energetically rich, difficult-to-acquire foods enhances female–male and male–male complementarities, thus altering the fitness of dads versus cads. We identify a tipping point where gains from provisioning overcome costs from paternity uncertainty and the dad strategy becomes viable. Stable polymorphic states are possible, meaning that dads need not necessarily eliminate cads. Our simulations suggest that with sufficient complementarities, dads can emerge even in the face of high paternity uncertainty. Our theoretical focus on ecological change as a primary factor affecting the trade-off between male mating and parenting effort suggests different possibilities for using paleo-climatic, archaeological, and genomic evidence to establish the timing of and conditions associated with emergence of paternal provisioning in the hominin lineage.

The evolution of raw material procurement strategies: A view from the deep sequence of Tabun Cave, Israel

Changes in the ways Paleolithic foragers exploited raw material sources are linked to mobility, the demands of production, and investment in quarrying. Here, we analyze the use of raw materials in a long series of superimposed layers from Tabun Cave dating to the Middle Pleistocene, attributed to the Lower and Middle Paleolithic periods. Using the cortex preserved on the surfaces of artifacts, including blanks, tools and cores, we distinguished between flints obtained from primary and secondary geological contexts. The results from Tabun Cave indicate that the exploitation of secondary sources was fairly common during the earlier part of the Lower Paleolithic sequence. It decreased during the later part of the Acheulo-Yabrudian complex of the Lower Paleolithic, coinciding with growing use of predetermined technological strategies, which demand high-quality raw materials. By the Middle Paleolithic, primary and secondary raw materials are generally designated for different reduction trajectories, suggesting a growing distinction and formalization of technological strategies. The need for the 'best' stone for Middle Paleolithic laminar and Levallois production may have necessitated increased investment in raw material procurement. During most of the Lower Paleolithic, raw material needs could have been met easily through a purely embedded strategy, in which raw material was collected while focusing on other activities. Starting in the late Acheulo-Yabrudian and especially during the Middle Paleolithic, the focus on primary geological contexts may have demanded greater planning of visits to raw material outcrops. In other words, in the Middle Paleolithic and possibly already during the very end of the Lower Paleolithic, raw material procurement had greater influence on patterns of movement through the landscape.

Prehistoric Perspectives on "Others" and "Strangers"

Social "connectivity" through time is currently considered as one of the major drivers of cultural transmission and cultural evolution. Within this framework, the interactions within and between groups are impacted by individuals' distinction of social relationships. In this paper, we focus on changes in a major aspect of social perceptions, "other" and "stranger." As inferred from the archaeological record, this perception among human groups gained importance during the course of the Pleistocene. These changes would have occurred due to the plasticity of cognitive mechanisms, in response to the demands on behavior along the trajectory of human social evolution. The concepts of "other" and "stranger" have received little attention in the archaeological discourse, yet they are fundamental in the perception of social standing. The property of being an "other" is defined by one's perception and is inherent to one's view of the world around oneself; when shared by a group it becomes a social cognitive construct. Allocating an individual the status of a "stranger" is a socially-defined state that is potentially transient. We hypothesize that, while possibly entrenched in deep evolutionary origins, the latter is a relatively late addition to socio-cognitive categorization, associated with increased sedentism, larger groups and reduced territorial extent as part of the process of Neolithization. We posit that "others" and "strangers" can be approached from contextual archaeological data, with inferences as regards the evolution of cognitive social categories. Our analysis focused on raw material studies, observations on style, and evidence for craft specialization. We find that contrary to the null hypothesis the archaeological record implies earlier emergence of complex socio-cognitive categorization. The cognitive, cultural and social processes involved in the maintenance and distinction between "others" and "strangers" can be defined as "self-domestication" that is still an on-going process.