scholarly journals Midsagittal Brain Variation among Non-Human Primates: Insights into Evolutionary Expansion of the Human Precuneus

2017 ◽  
Vol 90 (3) ◽  
pp. 255-263 ◽  
Author(s):  
Ana Sofia Pereira-Pedro ◽  
James K. Rilling ◽  
Xu Chen ◽  
Todd M. Preuss ◽  
Emiliano Bruner
Keyword(s):  
Homo Sapiens ◽  
Brain Size ◽  
Anatomical Variation ◽  
General Pattern ◽  
Dorsal Surface ◽  
Modern Human ◽  
Brain Morphology ◽  
Functional Region ◽  
Medial Side ◽  
Species Specific

The precuneus is a major element of the superior parietal lobule, positioned on the medial side of the hemisphere and reaching the dorsal surface of the brain. It is a crucial functional region for visuospatial integration, visual imagery, and body coordination. Previously, we argued that the precuneus expanded in recent human evolution, based on a combination of paleontological, comparative, and intraspecific evidence from fossil and modern human endocasts as well as from human and chimpanzee brains. The longitudinal proportions of this region are a major source of anatomical variation among adult humans and, being much larger in Homo sapiens, is the main characteristic differentiating human midsagittal brain morphology from that of our closest living primate relative, the chimpanzee. In the current shape analysis, we examine precuneus variation in non-human primates through landmark-based models, to evaluate the general pattern of variability in non-human primates, and to test whether precuneus proportions are influenced by allometric effects of brain size. Results show that precuneus proportions do not covary with brain size, and that the main difference between monkeys and apes involves a vertical expansion of the frontal and occipital regions in apes. Such differences might reflect differences in brain proportions or differences in cranial architecture. In this sample, precuneus variation is apparently not influenced by phylogenetic or allometric factors, but does vary consistently within species, at least in chimpanzees and macaques. This result further supports the hypothesis that precuneus expansion in modern humans is not merely a consequence of increasing brain size or of allometric scaling, but rather represents a species-specific morphological change in our lineage.

Seven Steps in the Evolution of the Human Imagination

2007 ◽  
Author(s):  
STEVEN MITHEN
Keyword(s):  
Cultural Change ◽  
Homo Sapiens ◽  
Brain Size ◽  
Modern Human ◽  
Clear Picture ◽  
Modern Humans ◽  
Creative Imagination ◽  
African Apes ◽  
Ways Of Thinking ◽  
Forms Of Knowledge

The modern human is a product of six million years of evolution wherein it is assumed that the ancestor of man resembles that of a chimpanzee. This assumption is based on the similarities of the ape-like brain size and post-cranial characteristics of the earliest hominid species to chimpanzees. Whilst it is unclear whether chimpanzees share the same foresight and contemplation of alternatives as with humans, it is nevertheless clear that chimpanzees lack creative imagination — an aspect of modern human imagination that sets humanity apart from its hominid ancestors. Creative imagination pertains to the ability to combine different forms of knowledge and ways of thinking to form creative and novel ideas. This chapter discusses seven critical steps in the evolution of the human imagination. These steps provide a clear picture of the gradual emergence of creative imagination in humans from their primitive origins as Homo sapiens some 200,000 years ago. This chronological evolution of the imaginative mind of humans involves both biological and cultural change that began soon after the divergence of the two lineages that led to modern humans and African apes.

Language and life history: A new perspective on the development and evolution of human language

2006 ◽  
Vol 29 (3) ◽  
pp. 259-280 ◽  
Author(s):  
John L. Locke ◽  
Barry Bogin
Keyword(s):  
Life History ◽  
Adult Development ◽  
Homo Sapiens ◽  
Human Life ◽  
Modern Human ◽  
Linguistic Knowledge ◽  
Human Language ◽  
Juvenile Period ◽  
Development Of Language ◽  
New Perspective

It has long been claimed that Homo sapiens is the only species that has language, but only recently has it been recognized that humans also have an unusual pattern of growth and development. Social mammals have two stages of pre-adult development: infancy and juvenility. Humans have two additional prolonged and pronounced life history stages: childhood, an interval of four years extending between infancy and the juvenile period that follows, and adolescence, a stage of about eight years that stretches from juvenility to adulthood. We begin by reviewing the primary biological and linguistic changes occurring in each of the four pre-adult ontogenetic stages in human life history. Then we attempt to trace the evolution of childhood and juvenility in our hominin ancestors. We propose that several different forms of selection applied in infancy and childhood; and that, in adolescence, elaborated vocal behaviors played a role in courtship and intrasexual competition, enhancing fitness and ultimately integrating performative and pragmatic skills with linguistic knowledge in a broad faculty of language. A theoretical consequence of our proposal is that fossil evidence of the uniquely human stages may be used, with other findings, to date the emergence of language. If important aspects of language cannot appear until sexual maturity, as we propose, then a second consequence is that the development of language requires the whole of modern human ontogeny. Our life history model thus offers new ways of investigating, and thinking about, the evolution, development, and ultimately the nature of human language.

scholarly journals Recent origin of low trabecular bone density in modern humans

2014 ◽  
Vol 112 (2) ◽  
pp. 366-371 ◽  
Author(s):  
Habiba Chirchir ◽  
Tracy L. Kivell ◽  
Christopher B. Ruff ◽  
Jean-Jacques Hublin ◽  
Kristian J. Carlson ◽  
...  
Keyword(s):  
Body Size ◽  
Trabecular Bone ◽  
Homo Sapiens ◽  
Modern Human ◽  
Homo Erectus ◽  
Lower Limbs ◽  
Modern Humans ◽  
Human Skeleton ◽  
Trabecular Density ◽  
Fossil Hominins

Humans are unique, compared with our closest living relatives (chimpanzees) and early fossil hominins, in having an enlarged body size and lower limb joint surfaces in combination with a relatively gracile skeleton (i.e., lower bone mass for our body size). Some analyses have observed that in at least a few anatomical regions modern humans today appear to have relatively low trabecular density, but little is known about how that density varies throughout the human skeleton and across species or how and when the present trabecular patterns emerged over the course of human evolution. Here, we test the hypotheses that (i) recent modern humans have low trabecular density throughout the upper and lower limbs compared with other primate taxa and (ii) the reduction in trabecular density first occurred in early Homo erectus, consistent with the shift toward a modern human locomotor anatomy, or more recently in concert with diaphyseal gracilization in Holocene humans. We used peripheral quantitative CT and microtomography to measure trabecular bone of limb epiphyses (long bone articular ends) in modern humans and chimpanzees and in fossil hominins attributed to Australopithecus africanus, Paranthropus robustus/early Homo from Swartkrans, Homo neanderthalensis, and early Homo sapiens. Results show that only recent modern humans have low trabecular density throughout the limb joints. Extinct hominins, including pre-Holocene Homo sapiens, retain the high levels seen in nonhuman primates. Thus, the low trabecular density of the recent modern human skeleton evolved late in our evolutionary history, potentially resulting from increased sedentism and reliance on technological and cultural innovations.

Signal-induced reorganization of the microtubular cytoskeleton in the ciliated protozoon Euplotes octocarinatus

1987 ◽  
Vol 87 (4) ◽  
pp. 555-564
Author(s):  
MARIA JERKA-DZIADOSZ ◽  
CHRISTINE DOSCHE ◽  
HANS-WERNER KUHLMANN ◽  
KLAUS HECKMANN
Keyword(s):  
General Pattern ◽  
Dorsal Surface ◽  
Cell Cortex ◽  
Circular Form ◽  
Transmission Electron ◽  
Microtubular Cytoskeleton ◽  
Subcortical Regions ◽  
Cell Changes ◽  
Euplotes Octocarinatus ◽  
Triton X

A predator-released substance induces the freshwater ciliate Euplotes octocarinatus to undergo, within a few hours, a drastic change in cell form that makes engulfment by the predator more difficult or even impossible. During this transformation, the outline of the cell changes from ovoid to circular and the size increases considerably. The cells cease dividing while they transform, but later continue divisional morphogenesis and maintain the circular form for many cell generations if the concentration of the predator factor is maintained. The microtubular cytoskeleton of Euplotes was studied by transmission electron microscopy of cells from which the cytoplasm had been extracted by mild treatment with Triton X-100. This procedure increased the visibility of microtubules, especially single microtubules located in the endoplasm. In transformed cells, a considerable increase in number of microtubular triads on the dorsal and ventral surfaces and the appearance of extra single microtubules between the dorsal triads was observed. However, certain interconnected groupings of microtubules located on the dorsal surface were greatly diminished after transformation. Intracytoplasmic microtubules were also more abundant in the enlarged cells than in the untreated ovoid ones. The spacing and general pattern of microtubules, however, appears to be the same in untreated and treated cells. We conclude from these observations that the transformation of Euplotes cells from their typical ovoid form into the enlarged circular form is accompanied by the mobilization and utilization of microtubules already present in subcortical regions and an assembly of new microtubules needed for support of the expanding cell cortex.

Aterian

2021 ◽  
Author(s):  
Elena A.A. Garcea
Keyword(s):  
Behavioral Plasticity ◽  
Homo Sapiens ◽  
Atlantic Coast ◽  
Modern Human ◽  
Middle Stone Age ◽  
Nile Valley ◽  
Mobility Patterns ◽  
North African ◽  
Behavioral Experiments ◽  
Wide Range

The Aterian is a North African late Middle Stone Age techno-complex. It is spread from the Atlantic coast in Morocco to the Middle Nile Valley in Sudan and from the Mediterranean hinterland to the Southern Sahara. Chronologically, it covers the period between c. 145,000 years bp and 29,000 bp, spanning across discontinuous, alternating dry (end of MIS 6 and MIS 4) and humid (MIS 5 and MIS 3) climatic phases. Few, but significant human remains indicate that the makers of the Aterian complex belong to early Homo sapiens. Their osteological features show affinities with the early anatomically modern human record in the Levant (Skhul and Qafzeh), suggesting that Aterian groups may have taken part in the initial dispersals out of Africa by Homo sapiens. Toolkits consist of a variety of implements not only made of stone but also of bone (points, spatulas, knives, and retouchers). They include tools that were lacking in earlier or other North African contemporary contexts, namely bifacial foliates, blades, perforators, burins, endscrapers, and particularly tanged pieces. Overemphasis on tanged tools often obscured the complexity of the Aterian, which instead displays a wide range of cultural and behavioral innovations. New mobility patterns and intra-site organization, as well as early symbolism with the use of Nassariidae shells and ochre, corroborate early fully complex behavior by these populations. Given the broad geographic and chronological extension of the Aterian, differences are evident at both local and regional scales. They suggest the development of a flexible and variable techno-complex mirroring considerable adaptive cognitive and behavioral plasticity derived from nonlinear processes. Such diversified behavioral experiments result from multiple and noncumulative trajectories due to different internal and external stimuli but are still part of a single cultural entity.

Sexual Selection, Timing and an X–Y Homologous Gene: Did Homo Sapiens Speciate on the Y Chromosome?

2004 ◽  
Author(s):  
Tim J. Crow
Keyword(s):  
Sexual Selection ◽  
Sex Chromosome ◽  
Homo Sapiens ◽  
Single Gene ◽  
Critical Role ◽  
Hominid Evolution ◽  
Homologous Gene ◽  
Chromosomal Change ◽  
Species Specific ◽  
Sex Chromosome Aneuploidies

This chapter provides a theory of the speciation of modern Homo sapiens, that a single gene played a critical role in the transition from a precursor species. The theory is founded upon the following: firstly, the premise that hemispheric asymmetry is the defining feature of the human brain and the only plausible correlate of language; secondly, an argument for a specific candidate region (the Xq21.3/Yp11.2 region of homology) based upon the reciprocal deficits associated with the sex chromosome aneuploidies, and the course of chromosomal change in hominid evolution; and thirdly, a particular evolutionary mechanism (sexual selection acting on an X-Y-linked gene) to account for species-specific modification of what initially was a saltational change. These postulates relate to the case of modern Homo sapiens. On the basis of the recent literature, the discussion argues that the third premise has general significance as a mechanism of speciation.

scholarly journals Evolution of Human Brain Size-Associated NOTCH2NL Genes Proceeds toward Reduced Protein Levels

2020 ◽  
Vol 37 (9) ◽  
pp. 2531-2548
Author(s):  
Gerrald A Lodewijk ◽  
Diana P Fernandes ◽  
Iraklis Vretzakis ◽  
Jeanne E Savage ◽  
Frank M J Jacobs
Keyword(s):  
Human Brain ◽  
Brain Size ◽  
Modern Human ◽  
Copy Number Variations ◽  
Optimal Dosage ◽  
Protein Coding ◽  
Protein Levels ◽  
Human Genomes ◽  
Coding Variants ◽  
Human Specific

Abstract Ever since the availability of genomes from Neanderthals, Denisovans, and ancient humans, the field of evolutionary genomics has been searching for protein-coding variants that may hold clues to how our species evolved over the last ∼600,000 years. In this study, we identify such variants in the human-specific NOTCH2NL gene family, which were recently identified as possible contributors to the evolutionary expansion of the human brain. We find evidence for the existence of unique protein-coding NOTCH2NL variants in Neanderthals and Denisovans which could affect their ability to activate Notch signaling. Furthermore, in the Neanderthal and Denisovan genomes, we find unusual NOTCH2NL configurations, not found in any of the modern human genomes analyzed. Finally, genetic analysis of archaic and modern humans reveals ongoing adaptive evolution of modern human NOTCH2NL genes, identifying three structural variants acting complementary to drive our genome to produce a lower dosage of NOTCH2NL protein. Because copy-number variations of the 1q21.1 locus, encompassing NOTCH2NL genes, are associated with severe neurological disorders, this seemingly contradicting drive toward low levels of NOTCH2NL protein indicates that the optimal dosage of NOTCH2NL may have not yet been settled in the human population.

Comment on "Ongoing Adaptive Evolution of ASPM, a Brain Size Determinant in Homo sapiens"

Science ◽  
2007 ◽  
Vol 316 (5823) ◽  
pp. 370b-370b ◽  
Author(s):  
F. Yu ◽  
R. S. Hill ◽  
S. F. Schaffner ◽  
P. C. Sabeti ◽  
E. T. Wang ◽  
...  
Keyword(s):  
Adaptive Evolution ◽  
Homo Sapiens ◽  
Brain Size
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