Inbreeding, Allee effects and stochasticity might be sufficient to account for Neanderthal extinction

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.

Assessing climatic impact on transition from Neanderthal to anatomically modern human population on Iberian Peninsula: a macroscopic perspective

The Iberian Peninsula is of particular interest for the research on the Neanderthal (NEA) to anatomically modern human (AMH) population transition. The AMHs arrived in Iberia last from Eastern Europe and thus any possible contacts between the two populations occurred here later than elsewhere. The transition process took place in the earlier part of the Marine Isotope Stage 3 (∼60-27 cal ka BP) as repeated and profound climate changes challenged the population stability. To investigate how climate change and population interactions influenced the transition, we combine climate data with archaeological-site data to reconstruct the Human Existence Potential, a measure of the probability of human existence, for both the NEA and AMH populations in the Greenland Interstadial 11-10 (GI11-10) and Stadial 10-9/Heinrich event 4 (GS10-9/HE4) times. It is found that during GS10-9/HE4, large parts of the peninsula became unsuitable for NEA human existence and the NEA settlement areas contracted to isolated coastal hot spots. As a consequence, the NEA networks became highly unstable, triggering the final collapse of the population. The AMHs arrived in Iberia in GI10 but were confined to patches in the northern most strip of the peninsula. They were soon facing the much colder climate of GS10-9/HE4, which prevented their further expansion or even caused a contraction of their settlement areas. Thus, due to the constellation of climate change and the dispersal of the two populations into different regions of the peninsula, it is unlikely that the NEAs and AMHs coexisted in extensive areas and the AMHs had a significant influence on the demography of the NEAs.

The revolution that still isn't: The origins of behavioral complexity in Homo sapiens

The behavioral origins of Homo sapiens can be traced back to the first material culture produced by our species in Africa, the Middle Stone Age (MSA). Beyond this broad consensus, the origins, patterns, and causes of behavioral complexity in modern humans remain debated. Here, we consider whether recent findings continue to support popular scenarios of: (1) a modern human 'package,' (2) a gradual and 'pan-African' emergence of behavioral complexity, and (3) a direct connection to changes in the human brain. Our geographically structured review shows that decades of scientific research have continuously failed to find a discrete threshold for a complete 'modernity package' and that the concept is theoretically obsolete. Instead of a continent-wide, gradual accumulation of complex material culture, the record exhibits a predominantly asynchronous presence and duration of many innovations across different regions of Africa. The emerging pattern of behavioral complexity from the MSA conforms to an intricate mosaic characterized by spatially discrete, temporally variable, and historically contingent trajectories. This archaeological record bears no direct relation to a simplistic shift in the human brain but rather reflects similar cognitive capacities that are variably manifested. The interaction of multiple causal factors constitutes the most parsimonious explanation driving the variable expression of complex behaviors, with demographic processes such as population structure, size, and connectivity playing a key role. While much emphasis has been given to innovation and variability in the MSA record, long periods of stasis and a lack of cumulative developments argue further against a strictly gradualistic nature in the record. Instead, we are confronted with humanity's deep, variegated roots in Africa, and a dynamic metapopulation that took many millennia to reach the critical mass capable of producing the ratchet effect commonly used to define contemporary human culture. Finally, we note a weakening link between 'modern' human biology and behavior from around 300 ka ago.

Possible Causes of Hypertrophic Osteoarthropathy in the La Ferrassie 1 Neanderthal

For over a century, researchers have been perplexed by the unique osteological findings on La Ferrassie 1 (LF1), one of the most complete Neanderthal remains ever found. In 1997, Fennel and Trinkaus proposed that LF1 suffered from hypertrophic osteoarthropathy (HOA), likely secondary to chronic thoracic infection or pulmonary malignancy. This disease process can have many etiologies, and no study has fully explored the possible origin of LF1's HOA. Ultimately, it is most likely that LF1's HOA etiology arose from one of the many infectious diseases that prehistoric Neanderthals were exposed to, specifically a chronic pulmonary RNA virus.

Entropy and Cross-Level Orderliness in Light of the Interconnection between the Neural System and Consciousness

Despite recent advances, the origin and utility of consciousness remains under debate. Using an evolutionary perspective on the origin of consciousness, this review elaborates on the promising theoretical background suggested in the temporospatial theory of consciousness, which outlines world-brain alignment as a critical predisposition for controlling behavior and adaptation. Such a system can be evolutionarily effective only if it can provide instant cohesion between the subsystems, which is possible only if it performs an intrinsic activity modified in light of the incoming stimulation. One can assume that the world-brain interaction results in a particular interference pattern predetermined by connectome complexity. This is what organisms experience as their exclusive subjective state, allowing the anticipation of regularities in the environment. Thus, an anticipative system can emerge only in a regular environment, which guides natural selection by reinforcing corresponding reactions and decreasing the system entropy. Subsequent evolution requires complicated, layered structures and can be traced from simple organisms to human consciousness and society. This allows us to consider the mode of entropy as a subject of natural evolution rather than an individual entity.

A refined chronology for the Middle and early Upper Paleolithic sequence of Riparo Mochi (Liguria, Italy)

The Riparo Mochi rock shelter, located on the Ligurian coast of Italy, is one of the most important early Upper Paleolithic sites on the Mediterranean rim. Its ∼10-m-deep stratigraphy comprises a Mousterian sequence, followed by various development stages of the Upper Paleolithic. A series of radiometric dates on marine shells bearing traces of human modification has provided a chronological framework for the final Mousterian and the Proto-Aurignacian of the site. Based on modeling results, the end of the Mousterian was dated between 44.0 and 41.8 ka cal BP (68% probability) and the beginning of the Proto-Aurignacian between 42.7 and 41.6 ka cal BP (68% probability). However, these estimates were based on a limited number of radiocarbon ages in the Mousterian levels. Here, we report new dating of the Mochi sequence using luminescence techniques, along with new radiocarbon measurements. The combination of these results using a Bayesian modeling approach allows for the first time the establishment of a more precise timing for the Mousterian occupation at the site. We show that Mousterian groups were already present at Riparo Mochi by at least 65 ka and continued to occupy the site for another 20 ka. The transition to the earliest Upper Paleolithic at the site is centered around 44.3-41.1 ka (95.4% probability), providing our best age estimate for the beginning of the Early Upper Paleolithic and the establishment of modern human groups in the Balzi Rossi. The sequence continues upward with a more evolved Aurignacian phase and a Gravettian phase starting at ∼26 ka or earlier.

Evolutionary origin and the development of consciousness

This review seeks to combine advances in anthropology and neuroscience to investigate the adaptive value of human consciousness. It uses an interdisciplinary perspective on the origin of consciousness to refute the most common fallacies in considering consciousness, particularly, disregarding the evolutionary origin of the subjective reality in looking for the neural correlates of consciousness and divorcing studies in neuroscience and behavioural sciences. Various explanations linked to consciousness in the field of neuroscience, supplemented with the theoretical explanation of an experience as an ongoing process of overlap between intrinsic neural dynamics and stimulation can be summarised as the stochastic dynamics of one's control system experienced by the individual in the form of subjective reality. This framework elaborates on the world-brain research program and lays foundation for the quantitative description of one's qualitative feelings and naturalistic science of consciousness. Furthermore, this study highlights the philosophical perspective of the inseparability between the physical correlates and the subjective reality contributing to the realistic ontology of conscious processes.

Reconstructing Neanderthal diet: The case for carbohydrates

Evidence for plants rarely survives on Paleolithic sites, while animal bones and biomolecular analyses suggest animal produce was important to hominin populations, leading to the perspective that Neanderthals had a very-high-protein diet. But although individual and short-term survival is possible on a relatively low-carbohydrate diet, populations are unlikely to have thrived and reproduced without plants and the carbohydrates they provide. Today, nutritional guidelines recommend that around half the diet should be carbohydrate, while low intake is considered to compromise physical performance and successful reproduction. This is likely to have been the same for Paleolithic populations, highlighting an anomaly in that the basic physiological recommendations do not match the extensive archaeological evidence. Neanderthals had large, energy-expensive brains and led physically active lifestyles, suggesting that for optimal health they would have required high amounts of carbohydrates. To address this anomaly, we begin by outlining the essential role of carbohydrates in the human reproduction cycle and the brain and the effects on physical performance. We then evaluate the evidence for resource availability and the archaeological evidence for Neanderthal diet and investigate three ways that the anomaly between the archaeological evidence and the hypothetical dietary requirements might be explained. First, Neanderthals may have had an as yet unidentified genetic adaptation to an alternative physiological method to spare blood glucose and glycogen reserves for essential purposes. Second, they may have existed on a less-than-optimum diet and survived rather than thrived. Third, the methods used in dietary reconstruction could mask a complex combination of dietary plant and animal proportions. We end by proposing that analyses of Paleolithic diet and subsistence strategies need to be grounded in the minimum recommendations throughout the life course and that this provides a context for interpretation of the archaeological evidence from the behavioral and environmental perspectives.

Climatic windows for human migration out of Africa in the past 300,000 years

Whilst an African origin of modern humans is well established, the timings and routes of their expansions into Eurasia are the subject of heated debate, due to the scarcity of fossils and the lack of suitably old ancient DNA. Here, we use high-resolution palaeoclimate reconstructions to estimate how difficult it would have been for humans in terms of rainfall availability to leave the African continent in the past 300k years. We then combine these results with an anthropologically and ecologically motivated estimate of the minimum level of rainfall required by hunter-gatherers to survive, allowing us to reconstruct when, and along which geographic paths, expansions out of Africa would have been climatically feasible. The estimated timings and routes of potential contact with Eurasia are compatible with archaeological and genetic evidence of human expansions out of Africa, highlighting the key role of palaeoclimate variability for modern human dispersals.

An emerging consensus in palaeoanthropology: demography was the main factor responsible for the disappearance of Neanderthals

The causes of Neanderthal disappearance about 40,000 years ago remain highly contested. Over a dozen serious hypotheses are currently endorsed to explain this enigmatic event. Given the relatively large number of contending explanations and the relatively large number of participants in the debate, it is unclear how strongly each contender is supported by the research community. What does the community actually believe about the demise of Neanderthals? To address this question, we conducted a survey among practicing palaeo-anthropologists (total number of respondents = 216). It appears that received wisdom is that demography was the principal cause of the demise of Neanderthals. In contrast, there is no received wisdom about the role that environmental factors and competition with modern humans played in the extinction process; the research community is deeply divided about these issues. Finally, we tested the hypothesis that palaeo-anthropologists' stand in the debate co-varies with their socio-political views and attitudes. We found no evidence for such a correlation.

Triangulating Neanderthal cognition: A tale of not seeing the forest for the trees

The inference of Neanderthal cognition, including their cultural and linguistic capabilities, has persisted as a fiercely debated research topic for decades. This lack of consensus is substantially based on inherent uncertainties in reconstructing prehistory out of indirect evidence as well as other methodological limitations. Further factors include systemic difficulties within interdisciplinary discourse, data artifacts, historic research biases, and the sheer scope of the relevant research. Given the degrees of freedom in interpretation ensuing from these complications, any attempt to find approximate answers to the yet unsettled pertinent discourse may not rest on single studies, but instead a careful and comprehensive interdisciplinary synthesis of findings. Triangulating Neanderthals' cognition by considering the plethora of data, diverse perspectives and aforementioned complexities present within the literature constitutes the currently most reliable pathway to tentative conclusions. While some uncertainties remain, such an approach paints the picture of an extensive shared humanity between anatomically modern humans and Neanderthals. This article is categorized under: Cognitive Biology > Evolutionary Roots of Cognition Linguistics > Evolution of Language.

Skin colour and vitamin D: An update

Homo sapiens evolved in East Africa and had dark skin, hair, and eyes, in order to protect against deleterious consequences of intensive UV radiation at equatorial latitudes. Intensive skin pigmentation was thought to bear the risk of inefficient vitamin D3 synthesis in the skin. This initiated the hypothesis that within the past 75 000 years, in which humans migrated to higher latitudes in Asia and Europe, the need for vitamin D3 synthesis served as an evolutionary driver for skin lightening. In this review, we summarize the recent archeogenomic reconstruction of population admixture in Europe and demonstrate that skin lightening happened as late as 5000 years ago through immigration of lighter pigmented populations from western Anatolia and the Russian steppe but not primarily via evolutionary pressure for vitamin D3 synthesis. We show that variations in genes encoding for proteins being responsible for the transport, metabolism and signalling of vitamin D provide alternative mechanisms of adaptation to a life in northern latitudes without suffering from consequences of vitamin D deficiency. This includes hypotheses explaining differences in the vitamin D status and response index of European populations.