The rise and fall of Homo sapiens sapiens

Human beings have broken the ecological 'law' that says that big, predatory animals are rare. Two crucial innovations in particular have enabled us to alter the planet to suit ourselves and thus permit unparalleled expansion: speech (which implies instant transmission of an open-ended range of conscious thoughts) and agriculture (which causes the world to produce more human food than unaided nature would do). However, natural selection has not equipped us with a long-term sense of self-preservation. Our population cannot continue to expand at its present rate for much longer, and the examples of many other species suggests that expansion can end in catastrophic collapse. Survival beyond the next century in a tolerable state seems most unlikely unless all religions and economies begin to take account of the facts of biology. This, if it occurred, would be a step in cultural evolution that would compare in import with the birth of agriculture.     

The Exploitation of Ungulate Bones in Homo neanderthalensis and Homo sapiens

Analysis of ungulate bones recovered from a number of Upper and Middle Palaeolithic sites in southern Italy revealed differences in the presence of anatomical elements. There is a lack of clear evidence of carnivore activities, and differences can be attributed to human activity. Indeed, these differences were probably due to different patterns of skeletal exploitation between Homo neanderthalensis and H. sapiens. Small limb bones (carpals, tarsals, sesamoids, long bone epiphyses and especially phalanges) are rarely found in Middle Palaeolithic deposits, but are abundant in the Upper Palaeolithic. The observation of unidentified bone fragments at these sites indicates that during the middle Palaeolithic, marrow extraction regarded essentially the treatment of long bones. First and second phalanges were not frequently used for this practice, but they were often fragmented by H. sapiens. Lack of these bones among the remains of meals of Neanderthal suggests that these bones were probably destroyed by their utilisation as fuel.     

Evolution of nakedness in Homo sapiens

Homo sapiens L. is the only existing primate species lacking in functionally effective thermally insulating fur. As all other primates have considerable hair covering, it has always been accepted that our ancestors must once have had a respectable amount of body hair. Unfortunately, fossils cannot help us when it comes to differences in skin and hair. Recent DNA analysis, however, has given us some idea of when and where the great denudation took place. A number of hypotheses have been proposed to account for this feature, but none of these has gained general acceptance. In this paper, I present these hypotheses in the light of current empirical evidence and discussion.     

Hypertrophy of the acetabulo-cristal buttress in Homo sapiens

In the early 1970s, excavation at the King site, a contact period Mississippian village in northwest Georgia, yielded the skeletal remains of a robust male (King 65) possessing marked hypertrophy of the acetabulo-cristal buttress. The buttress is morphologically similar to that of Plio-Pleistocene Homo but it is accompanied by an anatomically modern degree of thickening of the gluteal table of the ilium. Although the degree of cortical thickness of the gluteal table of the ilium is apparently species-specific, hypertrophy of the acetabulo-cristal buttress is developmental and may be expressed in all species of Homo. © 1993 Wiley-Liss, Inc.     

Tooth components of mandibular deciduous molars of Homo sapiens sapiens and Homo sapiens neanderthalensis: a radiographic study.

Tooth components of deciduous molars were measured from standardized radiographs of Homo sapiens sapiens and Homo sapiens neanderthalensis. Enamel height and width were greater in deciduous teeth of Homo sapiens sapiens than in Homo sapiens neanderthalensis and the differences were statistically significant (p less than 0.01). Dentin height showed no significant differences between the two groups, but enamel to floor of pulp chamber and pulp height and width dimensions were significantly greater in Homo sapiens neanderthalensis. Discriminant analysis carried out between groups, using deciduous tooth components, showed an accuracy of 98-100% for identification of Homo sapiens sapiens and 83-92% for identification of Homo sapiens neanderthalensis. The results obtained in this study on dental dimensions support the hypothesis of a distinct evolutionary line for Neanderthals.     

Genetic modulation of the senescent phenotype in Homo sapiens

While it is important to search for unifying mechanisms of aging among a variety of model systems, evolutionary arguments suggest that the pathophysiological details of senescence may be, to some extent, species specific. Moreover, in species that are characterized by extensive genetic heterogeneity, such as our own, one is likely to find kindreds with both "private" and "public" markers of aging. Crude estimates of the number of loci with the potential to modulate aspects of the senescent phenotype of man suggest that thousands of genes could be involved. No single locus appears to modulate all features. Some affect predominantly a single aspect ("unimodal progeroid syndromes"); familial Alzheimer's disease is discussed as a prototype. Linkage studies indicate genetic heterogeneity for autosomal dominant forms of the disease. Some loci affect multiple aspects of the phenotype ("segmental progeroid disorders"); the prototype is Werner's syndrome, an autosomal recessive. Cells from homozygotes behave like mutator strains and undergo accelerated senescence in vitro. Elucidation of the biochemical genetic basis of such abiotrophic disorders may shed light on specific aging processes in man.     

Reduction of maxillary molars in Homo sapiens sapiens: a different perspective.

Crown and cusp areas, and buccolingual and mesiodistal diameters of maxillary molars of complete upper tooth rows (30 males, 30 females) were analysed in order to quantify changes in size and shape from the first to the third molar. Uni- and multivariate analyses revealed the mesial cusps, in particular the protocone (mesiolingual cusp), to be more stable than the other cusps. Although there is a gradient in size from the first to third molar, shape changes were found to be marked. Overall, the findings are in keeping with the field theory and the hypotheses of environmental constraints on later developing teeth. However, not all of the results could be entirely explained by these concepts. Functional aspects seem to account for the relative stability of the protocone and the buccolingual crown diameter. It appears that this functional complex is relatively stable despite the overall reduction of tooth size, which is probably secondary to processes occurring in the jaws and the cranium. This finding may have implications for studies on tooth reduction between populations of different time periods.     

Genetic modulation of senescent phenotypes in Homo sapiens

Single-gene mutations can produce human progeroid syndromes--phenotypes that mimic usual or "normative" aging. These can be divided into two classes--those that have their impacts upon multiple organs and tissues (segmental progeroid syndromes) and those that have their major impacts upon a single organ or tissue (unimodal progeroid syndromes). The prototypic example of the former is the Werner syndrome, a condition caused by mutations of the RecQ family of DNA helicases. Research on the Werner syndrome and a surprising number of other progeroid syndromes support the importance of the maintenance of genomic stability as a partial antidote to aging. The prototypic examples of the latter are Alzheimer type dementias. The three gene products that cause rare autosomal-dominant early-onset varieties of these disorders all participate in the modulation of the beta amyloid precursor protein. They thus support the importance of the maintenance of proper protein processing and folding as a partial antidote to aging.     

Allometry between length and cross-sectional dimensions of the femur and tibia in Homo sapiens sapiens

Allometric equations relating length and cross-sectional geometric properties of the femur and tibia are generated using skeletal remains from three recent human population samples. Approximate isometry, or geometric similarity, is found both within and between samples. Cross-sectional areas scale to approximately length2, while second moments of area scale to approximately length4. It is shown that this is consistent with the maintenance of equivalent mechanical stress in long bones of different length under dynamic loadings in vivo. Other evidence indicates that bending and torsional loadings are more critical than axial loadings in the determination of lower limb bone cross-sectional dimensions.     

The complete complement of C1q-domain-containing proteins in Homo sapiens

The C-terminal domains of the A, B, C chains of C1q subcomponent of C1 complex represent a common structural motif, the C1q domain, that is found in a diverse range of proteins. We analyzed the human genome for the complete complement of this family and have identified a total of 31 independent gene sequences. The predominant organization of C1q-domain-containing (C1qDC) proteins includes a leading signal peptide, a collagen-like region of variable length, and a C-terminal C1q domain. There are 15 highly conserved residues within the C1q domain, among which 8 are invariant within the human gene set and these are predicted to cluster within the hydrophobic core of the protein. We suggest a 3-subfamily classification based on sequence homology. For some C1qDC-encoding genes, strict orthology has been retained throughout vertebrate evolution and these examples suggest a highly specific functional role for C1qDC proteins that has been under significant selective pressure. Alternatively, individual species have co-opted C1qDC proteins for roles that are highly specific to their biology, suggesting an evolutionary strategy of gene duplication and functional diversification. A more extensive analysis of the evolutionary relationship of C1qDC proteins reveals an ancient rooting, with clear members found in eubacterial species. Curiously, we have been unable to identify C1qDC-encoding genes in many eukaryotic genomcs, such as Sacchromyces cerivisae and C. elegans, suggesting that the retention or loss of this gene family throughout evolution has been sporadic.     

Rethinking the dispersal of Homo sapiens out of Africa

Current fossil, genetic, and archeological data indicate that Homo sapiens originated in Africa in the late Middle Pleistocene. By the end of the Late Pleistocene, our species was distributed across every continent except Antarctica, setting the foundations for the subsequent demographic and cultural changes of the Holocene. The intervening processes remain intensely debated and a key theme in hominin evolutionary studies. We review archeological, fossil, environmental, and genetic data to evaluate the current state of knowledge on the dispersal of Homo sapiens out of Africa. The emerging picture of the dispersal process suggests dynamic behavioral variability, complex interactions between populations, and an intricate genetic and cultural legacy. This evolutionary and historical complexity challenges simple narratives and suggests that hybrid models and the testing of explicit hypotheses are required to understand the expansion of Homo sapiens into Eurasia.     

Comparative in vivo antiangiogenic effects of calreticulin from Trypanosoma cruzi and Homo sapiens sapiens

Angiogenesis is a complex multi-step process of neovascularization arising from preexisting blood vessels whose generation is regulated by pro- and anti-angiogenic factors. Both Trypanosoma cruzi calreticulin (TcCRT) and its human counterpart (HuCRT) are antiangiogenic. This is the first report where the TcCRT and HuCRT anti-angiogenic properties are compared in vivo. In the chick embryonic chorioallantoid membrane assay (CAM) and at equimolar concentrations, TcCRT displayed significantly higher antiangiogenic activities than its human counterpart. LPS had marginal effects at the concentrations present in the recombinant protein preparations and the TcCRT antiangiogenic effects were largely inhibited by specific polyclonal antibodies, thus, reinforcing the fact that the observed TcCRT effects can be attributed to the parasite-derived molecule and not to the endotoxin. The antiangiogenic TcCRT effects correlate with its anti-tumor in vivo effects, as recently shown in our laboratory.     

Visualizing patterns of craniofacial shape variation in Homo sapiens

The geometric morphometric analysis of shape variation in complex biological structures such as the human skull poses a number of specific challenges: the registration of homologous morphologies, the treatment of bilateral symmetry, the graphical representation of form variability in three dimensions and the interpretation of the results in terms of differential growth processes. To visualize complex patterns of shape change, we propose an alternative to classical Cartesian deformation grids in the style of D'Arcy W. Thompson. Reference to the surface structures of the organism under investigation permits a comprehensive visual grasp of shape change and its tentative interpretation in terms of differential growth. The application of this method to the analysis of human craniofacial shape variation reveals distinct modes of growth and development of the neurocranial and viscerocranial regions of the skull. Our data further indicate that variations in the orientation of the viscerocranium relative to the neurocranium impinge on the shapes of the face and the cranial vault.     

Percussive technology in human evolution: an introduction to a comparative approach in fossil and living primates

Percussive technology is part of the behavioural suite of several fossil and living primates. Stone Age ancestors used lithic artefacts in pounding activities, which could have been most important in the earliest stages of stone working. This has relevant evolutionary implications, as other primates such as chimpanzees and some monkeys use stone hammer-and-anvil combinations to crack hard-shelled foodstuffs. Parallels between primate percussive technologies and early archaeological sites need to be further explored in order to assess the emergence of technological behaviour in our evolutionary line, and firmly establish bridges between Primatology and Archaeology. What are the anatomical, cognitive and ecological constraints of percussive technology? How common are percussive activities in the Stone Age and among living primates? What is their functional significance? How similar are archaeological percussive tools and those made by non-human primates? This issue of Phil. Trans. addresses some of these questions by presenting case studies with a wide chronological, geographical and disciplinary coverage. The studies presented here cover studies of Brazilian capuchins, captive chimpanzees and chimpanzees in the wild, research on the use of percussive technology among modern humans and recent hunter–gatherers in Australia, the Near East and Europe, and archaeological examples of this behaviour from a million years ago to the Holocene. In summary, the breadth and depth of research compiled here should make this issue of Philosophical Transactions of the Royal Society B, a landmark step forward towards a better understanding of percussive technology, a unique behaviour shared by some modern and fossil primates.     

Accelerated evolution of nervous system genes in the origin of Homo sapiens

Human evolution is characterized by a dramatic increase in brain size and complexity. To probe its genetic basis, we examined the evolution of genes involved in diverse aspects of nervous system biology. We found that these genes display significantly higher rates of protein evolution in primates than in rodents. Importantly, this trend is most pronounced for the subset of genes implicated in nervous system development. Moreover, within primates, the acceleration of protein evolution is most prominent in the lineage leading from ancestral primates to humans. Thus, the remarkable phenotypic evolution of the human nervous system has a salient molecular correlate, i.e., accelerated evolution of the underlying genes, particularly those linked to nervous system development. In addition to uncovering broad evolutionary trends, our study also identified many candidate genes--most of which are implicated in regulating brain size and behavior--that might have played important roles in the evolution of the human brain.