Neanderthal coexistence with Homo sapiens in Europe was affected by herbivore carrying capacity.

It has been proposed that climate change and the arrival of modern humans in Europe affected the disappearance of Neanderthals due to their impact on trophic resources; however, it has remained challenging to quantify the effect of these factors. By using Bayesian age models to derive the chronology of the European Middle to Upper Paleolithic transition, followed by a dynamic vegetation model that provides the Net Primary Productivity, and a macroecological model to compute herbivore abundance, we show that in continental regions where the ecosystem productivity was low or unstable, Neanderthals disappeared before or just after the arrival of Homo sapiens. In contrast, regions with high and stable productivity witnessed a prolonged coexistence between both species. The temporal overlap between Neanderthals and H. sapiens is significantly correlated with the carrying capacity of small- and medium-sized herbivores. These results suggest that herbivore abundance released the trophic pressure of the secondary consumers guild, which affected the coexistence likelihood between both human species.

Subsistence of early anatomically modern humans in Europe as evidenced in the Protoaurignacian occupations of Fumane Cave, Italy.

Documenting the subsistence strategies developed by early modern humans is relevant for understanding the success of their dispersal throughout Eurasia. Today, we know that there was not a single colonization event and that the process was progressive while coping with the MIS3 abrupt climatic oscillations. Modern humans expanded into the continent by adapting to different topographic situations and by exploiting resources in diverse ecological niches. The northern part of Italy is one of the first European regions where early modern humans are documented. Here, we present the subsistence regimen adopted by the Protoaurignacian groups in two different levels in Fumane Cave based on archaeozoological data. New radiocarbon dates confirm an overlap between Uluzzian and Protoaurignacian occupations, around 42 and 41,000 cal BP, and reveal that modern humans occupied the cave from GI10 to GS9, the last level coinciding with the Heinrich Event 4. The data indicate seasonal site occupations during late spring/summer and that prey exploitation was focused mostly on ibex and chamois, killed in nearby areas. The whole faunal assemblage suggests the presence of early modern humans in a cold environment with mostly open landscapes and patchy woodlands. The estimation of net primary productivity (NPP) in Fumane, compared with other contemporaneous Italian sites, reflects how the NPP fluctuations in the Prealpine area, where Fumane is located, affected the biotic resources in contrast to known Mediterranean sites. From a pan-European perspective, the spatiotemporal fluctuation of the NPP versus the subsistence strategies adopted by Protoaurignacian groups in the continent supports rapid Homo sapiens dispersal and resilience in a mosaic of environments that were affected by significant climate changes.

Evaluating the human capacity of carrying loads without costs: A scoping review of the Free-Ride phenomenon.

OBJECTIVES: Several researchers have obtained discordant results testing the human capability to transport loads without added locomotion costs. Carrying loads has an extended relevance to human ecology, thus a review of the Free-Ride phenomenon detection according to the existing literature is needed. METHOD: A search was made in November 2021 in SCOPUS, Google Scholar, and Web of Science to identify studies comparing the energy expenditure of loaded and unloaded locomotion. Descriptive percentages were calculated with the data obtained from each study, and a Chi-squared (χ2 ) independency test and a contingency table were applied to observe the relationship between sample characteristics, experimental procedures, and the detection of the Free-Ride. RESULTS: A total of 45 studies met the inclusion criteria. Eighty two percent do not detect the Free-Ride phenomenon. The general detection is independent of sex, experience, load position, load size, and speed (p value >.05) although the papers detecting the Free-Ride have some common characteristics. CONCLUSION: The literature does not support a Free-Ride capacity, but future research testing this phenomenon should consider the load size, the load position, the level of expertise, or the speed. As the Free-Ride is not generalizable, it can be hypothesized that other mechanisms may have emerged during human evolution to buffer the energetic demands of load carrying.

Daily Distance Traveled Is Associated with Greater Brain Size in Primates.

Explanations for the brain size increments through primate and, particularly, human evolution are numerous. Commonly, these hypotheses rely on the influence that behavioral and ecological variables have on brain size in extant primates, such as diet quality, social group size, or home range (HR) area. However, HR area does not reflect the time spent moving. As such, it has not been properly addressed whether the effort involved in movement could have affected brain size evolution in primates. This study aimed to test the influence of daily movement on primates' brain sizes, controlling for these other behavioral and ecological factors. We used a large comparative dataset of extant primate species and phylogenetic comparative methods. Our results show a significant correlation between daily movement and brain mass, which is not explained by the influence of diet, social group size, HR, or body mass. Hence, from an evolutionary timescale, a longer daily movement distance is not a constraining factor for the energetic investment in a larger brain. On the contrary, increased mobility could have contributed to brain mass incrementations through evolution.

No sex differences in the economy of load-carriage.

OBJECTIVES: Load transport activities are of vital importance to current foragers for daily subsistence tasks; thus, it has been suggested that these practices have transformed physical and behavioral characteristics through human evolution. Together with the procurement targets and strategies, the transportation of resources acquired while foraging is strongly influenced by the sex of the foragers. In hunter-gatherer societies, women, despite their smaller body size, usually carry heavier burdens than males. In this study, whether those behavioral differences can be explained by a different economy of load-carriage by sex, irrespective of the body mass of the individuals, is investigated. MATERIAL AND METHODS: The energy expenditure of a sample of 48 volunteers (21 females, 27 males) during a set of locomotion and burden transport trials was monitored. Two indexes were computed to compare the increment in the cost of locomotion relative to the load carried by sex. RESULTS: The results demonstrate that both males and females, carrying the same relative loads, experience the same increment over the cost of their unloaded locomotion. Therefore, apart from obvious differences in body mass, there is no evidence of a dissimilar economy favoring one sex over the other that would explain the differences in load-carriage activities observed among current foraging populations. CONCLUSIONS: These outcomes provide new conclusions about the constraints of the behavioral ecology of burden transport activities, and highlight the necessity to reevaluate, from an evolutionary perspective, the ideas about the sexual division of subsistence labor in hunter-gatherer and agriculturalist populations.