Raphael Sirtoli

Bio: Raphael Sirtoli is an academic researcher from University of Minho. The author has contributed to research in topics: Mesolithic & Human evolution. The author has an hindex of 1, co-authored 2 publications receiving 6 citations.

The evolution of the human trophic level during the Pleistocene.

Abstract: The human trophic level (HTL) during the Pleistocene and its degree of variability serve, explicitly or tacitly, as the basis of many explanations for human evolution, behavior, and culture. Previous attempts to reconstruct the HTL have relied heavily on an analogy with recent hunter-gatherer groups' diets. In addition to technological differences, recent findings of substantial ecological differences between the Pleistocene and the Anthropocene cast doubt regarding that analogy's validity. Surprisingly little systematic evolution-guided evidence served to reconstruct HTL. Here, we reconstruct the HTL during the Pleistocene by reviewing evidence for the impact of the HTL on the biological, ecological, and behavioral systems derived from various existing studies. We adapt a paleobiological and paleoecological approach, including evidence from human physiology and genetics, archaeology, paleontology, and zoology, and identified 25 sources of evidence in total. The evidence shows that the trophic level of the Homo lineage that most probably led to modern humans evolved from a low base to a high, carnivorous position during the Pleistocene, beginning with Homo habilis and peaking in Homo erectus. A reversal of that trend appears in the Upper Paleolithic, strengthening in the Mesolithic/Epipaleolithic and Neolithic, and culminating with the advent of agriculture. We conclude that it is possible to reach a credible reconstruction of the HTL without relying on a simple analogy with recent hunter-gatherers' diets. The memory of an adaptation to a trophic level that is embedded in modern humans' biology in the form of genetics, metabolism, and morphology is a fruitful line of investigation of past HTLs, whose potential we have only started to explore.

Human oral microbiome cannot predict Pleistocene starch dietary level, and dietary glucose consumption is not essential for brain growth

Abstract: Fellows Yates et al. (1) find amylase-binding bacteria in Late Pleistocene Neandertals and Homo sapiens dental calculus and project a starch-rich diet early and throughout human evolution and an essential role for starch in brain expansion. We recently argued for the need to use more paleobiological-type evidence to reconstruct past trophic levels (2), so welcome the evidence they present as a valuable contribution. While groundbreaking in many respects, we fail to see how Fellows Yates et al.’s results support some of their critical conclusions concerning the role of high starch consumption in Homo evolution. Our main contention is with the attempt to tie a “core” Late-Terminal … [↵][1]1To whom correspondence may be addressed. Email: bendor.michael{at}gmail.com. [1]: #xref-corresp-1-1

Prey Size Decline as a Unifying Ecological Selecting Agent in Pleistocene Human Evolution

Abstract: We hypothesize that megafauna extinctions throughout the Pleistocene, that led to a progressive decline in large prey availability, were a primary selecting agent in key evolutionary and cultural changes in human prehistory. The Pleistocene human past is characterized by a series of transformations that include the evolution of new physiological traits and the adoption, assimilation, and replacement of cultural and behavioral patterns. Some changes, such as brain expansion, use of fire, developments in stone-tool technologies, or the scale of resource intensification, were uncharacteristically progressive. We previously hypothesized that humans specialized in acquiring large prey because of their higher foraging efficiency, high biomass density, higher fat content, and the use of less complex tools for their acquisition. Here, we argue that the need to mitigate the additional energetic cost of acquiring progressively smaller prey may have been an ecological selecting agent in fundamental adaptive modes demonstrated in the Paleolithic archaeological record. We describe several potential associations between prey size decline and specific evolutionary and cultural changes that might have been driven by the need to adapt to increased energetic demands while hunting and processing smaller and smaller game.

Lower Paleolithic Winds of Change: Prepared Core Technologies and the Onset of the Levallois Method in the Levantine Late Acheulian

Abstract: The life cycle of a successful technological innovation usually follows a well-known path: a slow inception, gradual assimilation of the technology, an increase in its frequency up to a certain peak, and then a decline. These different phases are characterized not only by varying frequency of use but also by degree of standardization and distinguishability. The Levallois method, a sophisticated Middle Paleolithic technology aimed at producing desired stone items of predetermined morphology, is one such innovation. It has been repeatedly suggested that the Levallois method originated within earlier Lower Paleolithic Acheulian industries, and this work contributes to this discussion. We analyze the reduction trajectory of prepared cores and predetermined blanks from the late Acheulian sites of Jaljulia and Revadim, adding important new evidence for the Lower Paleolithic origins of the Levallois method and its adoption and assimilation in the human stone-tool repertoire of this period in the Levant. Revadim and Jaljulia also provide a rare opportunity to study patterns in the early assimilation of technological innovations. These sites yielded rich lithic assemblages typical of the late Acheulian in the Levant. The assemblages include handaxes but are mostly dominated by flake production technologies and flake-tools. The early appearance of prepared cores at both sites signals, in our view, the inception of concepts related to the Levallois method, termed here proto-Levallois, in the late Acheulian Levant. Through a detailed analysis of prepared cores and their products, we are able to characterize the early stages of assimilation of this method, using it as a case study in a broader discussion of the adoption and assimilation of technological innovations during Lower Paleolithic times.

Evolutionary ecology of language origins through confrontational scavenging

Abstract: A dynamic model and an agent-based simulation model implementing the assumptions of the confrontational scavenging hypothesis on early protolanguage as an adaptive response of Homo erectus to gradual change in their habitat has been developed and studied. The core assumptions of the hypothesis and the model scenario are the pre-adaptation of our ancestors to occupy the ecological niche that they constructed for themselves by having evolved displaced communication and a rudimentary tool manufacture, two features allowing them to use a new, concentrated and abundant resource—megafauna carrion—on the savannahs replacing arboreal habitats owing to the drying climate of East Africa at about 2 Ma. The shift in diet required coordinated cooperation by the hominin scavengers confronted with concurrent predators. Power scavenging compelled displaced symbolic communication featuring a limited semantic range; syntax was not yet required. We show that phenotypic evolution on the accuracy of information transfer between cooperating hominins is a necessary and sufficient condition for the population of agents to survive the diet shift. Both the individual and the group fitness of the hominin horde increased with the accuracy of their protolanguage, with decreasing time allocated to foraging and thus more time left for culture. This article is part of the theme issue ‘Human socio-cultural evolution in light of evolutionary transitions’.