Evolution Of Homo Research Articles

Rise of the Human Predator

The article discusses when and how the ancestors of the genus Homo, which includes modern humans (H. sapiens), became skilled hunters. Topics include debate about the role of hunting in human evolution, research by Neil T. Roach of George Washington University and colleagues that suggests a link between natural selection, human anatomy, and hunting, an overview of Homo evolution, and the impact of Homo's shift from a vegetarian diet to one that included meat.

On the relationships of postcanine tooth size with dietary quality and brain volume in primates: implications for hominin evolution.

Brain volume and cheek-tooth size have traditionally been considered as two traits that show opposite evolutionary trends during the evolution of Homo. As a result, differences in encephalization and molarization among hominins tend to be interpreted in paleobiological grounds, because both traits were presumably linked to the dietary quality of extinct species. Here we show that there is an essential difference between the genus Homo and the living primate species, because postcanine tooth size and brain volume are related to negative allometry in primates and show an inverse relationship in Homo. However, when size effects are removed, the negative relationship between encephalization and molarization holds only for platyrrhines and the genus Homo. In addition, there is no general trend for the relationship between postcanine tooth size and dietary quality among the living primates. If size and phylogeny effects are both removed, this relationship vanishes in many taxonomic groups. As a result, the suggestion that the presence of well-developed postcanine teeth in extinct hominins should be indicative of a poor-quality diet cannot be generalized to all extant and extinct primates.

Frontal Brain Expansion During Development Using MRI and Endocasts: Relation to Microcephaly and Homo floresiensis

A major hall of hominid brain evolution is an expansion of the frontal lobes. To determine if a similar trajectory occurs during modern human development, the MRI scans of 118 living infants, children, and adolescents were reviewed and three specific measurements obtained: frontal width (FW), maximal cerebral width (MW), and maximal cerebral length (ML). The infantile brain is uniformly wide but relatively short, with near equal FW and MW. The juvenile brain exhibits a wider MW than FW, while FW of the adolescent brain expands to nearly equal MW, concurrent with an increase in ML. The preferential frontal lobe expansion during modern human development parallels that observed during the evolution of Homo. In 17 microcephalic individuals, only 6 (35%) exhibited preferential frontal lobe hypoplasia, presumably a reflection of multiple etiologies that adversely affect differing brain regions. Compared to 79 modern human adult endocasts and 12 modern microcephalic endocasts, LB1 (Homo floresiensis) clustered more consistently with the microcephalic sample than with the normocephalic sample.

Origins and Evolution of GenusHomo

Recent fossil and archaeological finds have complicated our interpretation of the origin and early evolution of genus Homo. Using an integrated data set from the fossil record and contemporary human and nonhuman primate biology, we provide a fresh perspective on three important shifts in human evolutionary history: (1) the emergence of Homo, (2) the transition between non-erectus early Homo and Homo erectus, and (3) the appearance of regional variation in H. erectus. The shift from Australopithecus to Homo was marked by body and brain size increases, a dietary shift, and an increase in total daily energy expenditure. These shifts became more pronounced in H. erectus, but the transformation was not as radical as previously envisioned. Many aspects of the human life history package, including reduced dimorphism, likely occured later in evolution. The extant data suggest that the origin and evolution of Homo was characterized by a positive feedback loop that drove life history evolution. Critical to this process were probably cooperative breeding and changes in diet, body composition, and extrinsic mortality risk. Multisystem evaluations of the behavior, physiology, and anatomy of extant groups explicitly designed to be closely proxied in the fossil record provide explicit hypotheses to be tested on future fossil finds.

Body Size, Body Shape, and the Circumscription of the Genus Homo

Since the 1984 discovery of the Nariokotome Homo erectus/Homo ergaster skeleton, it has been almost axiomatic that the emergence of Homo (sensu stricto) was characterized by an increase in body size to the modern human condition and an autapomorphic shift in body proportions to those found today. This was linked to a behavioral shift toward more intensive carnivory and wider ranging in the genus Homo. Recent fossil discoveries and reanalysis of the Nariokotome skeleton suggest a more complex evolutionary pattern. While early Homo tend to be larger than Australopithecus/Paranthropus, they were shorter on average than people today. Reanalysis of the Nariokotome pelvis along with the discovery of additional early and middle Pleistocene pelves indicate that a narrow bi-iliac (pelvic) breadth is an autapomorphy specific to Homo sapiens. Likewise, it appears that at least some early Homo (even those referred to H. ergaster/H. erectus) were characterized by higher humero-femoral indices than the H. sapiens average. All these data suggest a pattern of mosaic postcranial evolution in Homo with implications for the increased ranging/carnivory model of the origin of Homo as well as for which species are included within the Homo hypodigm.

The Effects of Mortality, Subsistence, and Ecology on Human Adult Height and Implications forHomoEvolution

The increase in body size observed with the appearance and evolution of Homo is most often attributed to thermoregulatory and locomotor adaptations to environment; increased reliance on animal protein and fat; or increased behavioral flexibility, provisioning, and cooperation leading to decreased mortality rates and slow life histories. It is not easy to test these hypotheses in the fossil record. Therefore, understanding selective pressures shaping height variability in living humans might help to construct models for the interpretation of body size variation in the hominins. Among human populations, average male height varies extensively (145 cm–183 cm); a similar range of variation is found in Homo erectus (including African and Georgian samples). Previous research shows that height in human populations covaries with life history traits and variations in mortality rates and that different environments affect adult height through adaptations related to thermoregulation and nutrition. We investigate the interactions between life history traits, mortality rates, environmental setting, and subsistence for 89 small-scale societies. We show that mortality rates are the primary factor shaping adult height variation and that people in savanna are consistently taller than people in forests. We focus on relevant results for interpreting the evolution of Homo body size variability.

Human Biology and the Origins ofHomo

New fossil discoveries relevant to the origin of Homo have overturned conventional wisdom about the nature of the australopiths and early Homo, and particularly Homo erectus (including Homo ergaster). They have eroded prior assumptions about the differences between these genera and complicated interpretations for the origin and evolution of Homo. This special issue surveys what is now known about the fossil evidence and the environmental context of early Homo. It also moves beyond the hard evidence and sets the stage for integrated, multidisciplinary studies to provide a framework for interpretation of the hard evidence. The underlying premise is that to understand the adaptive shifts at the origin of Homo, it is essential to have a solid understanding of how and why modern humans and other animals vary. Contributors to this issue include paleoanthropologists, human biologists, behavorialists, and modelers. We tasked each with bringing her or his special expertise to bear on the question of the origins an...

Environmental and Behavioral Evidence Pertaining to the Evolution of Early Homo

East African paleoenvironmental data increasingly inform an understanding of environmental dynamics. This understanding focuses less on habitat reconstructions at specific sites than on the regional trends, tempo, and amplitudes of climate and habitat change. Sole reliance on any one indicator, such as windblown dust or lake sediments, gives a bias toward strong aridity or high moisture as the driving force behind early human evolution. A synthesis of geological data instead offers a new paleoenvironmental framework in which alternating intervals of high and low climate variability provided the dynamic context in which East African Homo evolved. The Oldowan behavioral record presents further clues about how early Homo and Homo erectus responded to East African environmental change. Shifting conditions of natural selection, which were triggered by climatic variability, helped shape the adaptability of Oldowan hominins. Together, the behavioral and environmental evidence indicates the initial adaptive foundation for the dispersal of H. erectus and the persistence of Homo. In particular, overall dietary expansion made possible by the making and transport of stone tools compensated for increased locomotor and foraging costs and provided effective behavioral-ecological responses to resource instability during the early evolution of Homo.

Male Life History, Reproductive Effort, and the Evolution of the GenusHomo

The evolution of male life history traits was central to the emergence of the genus Homo. Compared with earlier hominins, changes in the behavioral and physiological mechanics of growth, survivorship, reproductive effort, and senescence all likely contributed to shifts in how males contributed to the evolution of our genus. For example, the range of paternal investment in modern Homo sapiens is unusual compared with most mammals and primates, all but certainly contributing to the evolution of the suite of life history traits that define Homo, including high fertility, large bodies, altricial offspring, large brains, and long lives. Moreover, the extensive range of phenotypic and behavioral variation in somatic and behavioral reflections of male reproductive effort across modern H. sapiens is especially noteworthy. We propose that selection for a broad range of variation in traits reflective of male reproductive effort was important to the evolution of Homo. We examine factors that contribute to this varia...

Primates

Primates

Icy isolation may have led to new human species: Cold‐climate refuges possibly influenced Homo evolution

Science NewsVolume 181, Issue 7 p. 5-6 In the News Icy isolation may have led to new human species: Cold-climate refuges possibly influenced Homo evolution Bruce Bower, Bruce BowerSearch for more papers by this author Bruce Bower, Bruce BowerSearch for more papers by this author First published: 28 March 2012 https://doi.org/10.1002/scin.5591810703Citations: 1Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume181, Issue77 April 2012Pages 5-6 RelatedInformation

Dental microwear texture analysis and diet in the Dmanisi hominins

Reconstructions of foraging behavior and diet are central to our understanding of fossil hominin ecology and evolution. Current hypotheses for the evolution of the genus Homo invoke a change in foraging behavior to include higher quality foods. Recent microwear texture analyses of fossil hominin teeth have suggested that the evolution of Homo erectus may have been marked by a transition to a more variable diet. In this study, we used microwear texture analysis to examine the occlusal surface of 2 molars from Dmanisi, a 1.8 million year old fossil hominin site in the Republic of Georgia. The Dmanisi molars were characterized by a moderate degree of surface complexity ( Asfc), low textural fill volume ( Tfv), and a relatively low scale of maximum complexity ( Smc), similar to specimens of early African H. erectus. While caution must be used in drawing conclusions from this small sample ( n = 2), these results are consistent with continuity in diet as H. erectus expanded into Eurasia.

Evolution of the base of the brain in highly encephalized human species.

The increase of brain size relative to body size-encephalization-is intimately linked with human evolution. However, two genetically different evolutionary lineages, Neanderthals and modern humans, have produced similarly large-brained human species. Thus, understanding human brain evolution should include research into specific cerebral reorganization, possibly reflected by brain shape changes. Here we exploit developmental integration between the brain and its underlying skeletal base to test hypotheses about brain evolution in Homo. Three-dimensional geometric morphometric analyses of endobasicranial shape reveal previously undocumented details of evolutionary changes in Homo sapiens. Larger olfactory bulbs, relatively wider orbitofrontal cortex, relatively increased and forward projecting temporal lobe poles appear unique to modern humans. Such brain reorganization, beside physical consequences for overall skull shape, might have contributed to the evolution of H. sapiens' learning and social capacities, in which higher olfactory functions and its cognitive, neurological behavioral implications could have been hitherto underestimated factors.

Nasal Septal and Premaxillary Developmental Integration: Implications for Facial Reduction in Homo

The influence of the chondrocranium in craniofacial development and its role in the reduction of facial size and projection in the genus Homo is incompletely understood. As one component of the chondrocranium, the nasal septum has been argued to play a significant role in human midfacial growth, particularly with respect to its interaction with the premaxilla during prenatal and early postnatal development. Thus, understanding the precise role of nasal septal growth on the facial skeleton is potentially informative with respect to the evolutionary change in craniofacial form. In this study, we assessed the integrative effects of the nasal septum and premaxilla by experimentally reducing facial length in Sus scrofa via circummaxillary suture fixation. Following from the nasal septal-traction model, we tested the following hypotheses: (1) facial growth restriction produces no change in nasal septum length; and (2) restriction of facial length produces compensatory premaxillary growth due to continued nasal septal growth. With respect to hypothesis 1, we found no significant differences in septum length (using the vomer as a proxy) in our experimental (n = 10), control (n = 9) and surgical sham (n = 9) trial groups. With respect to hypothesis 2, the experimental group exhibited a significant increase in premaxilla length. Our hypotheses were further supported by multivariate geometric morphometric analysis and support an integrative relationship between the nasal septum and premaxilla. Thus, continued assessment of the growth and integration of the nasal septum and premaxilla is potentially informative regarding the complex developmental mechanisms that underlie facial reduction in genus Homo evolution.

The fellowship of the hobbit: the fauna surroundingHomo floresiensis

AbstractThe Late Pleistocene Flores fauna shows a pattern observed on many other islands. It is neither aberrant nor exclusive, but the result of non‐random selective forces acting upon an impoverished and disharmonic insular fauna. By comparing the Flores vertebrate fauna with other fossil insular biotas, it is apparent that the evolution ofHomo floresiensisis part of a general pattern affecting all the inhabitants of Pleistocene Flores. Vertebrate evolution on Flores appears to have been characterized by phylogenetic continuity, low species richness and a disharmonic fauna. All three aspects stem from the isolated position of the island and have resulted in the distinct morphological characteristics of the Flores fauna. Evidence reviewed herein shows that features exhibited byH. floresiensis, such as small stature, a small brain, relatively long arms, robust lower limbs and long feet, are not unique, but are shared by other insular taxa. Therefore, the evolution ofH. floresiensiscan be explained by existing models of insular evolution and followed evolutionary pathways similar to those of the other terrestrial vertebrates inhabiting Pleistocene Flores.

Could empathy for animals have been an adaptation in the evolution of Homo sapiens?

AbstractIn humans, empathy has emotional and cognitive components, both of which are linked to caring and nurturant behaviour. Variations in each of these facets of empathy were likely to have been accessible to natural selection during the evolution of Homo, although the likely details of their respective adaptive values has so far only been considered in the context of intraspecific (human-human) behaviour. We propose that evolutionary psychology may provide a useful additional framework for examining why humans feel empathy for certain animals but not others. Phobias towards noxious animals, such as snakes and spiders, have been explained in terms of gene-culture co-evolution, but the possibility of an analogous ‘biophilia’ directed towards other animals has received less attention. The redirection of primarily intraspecific nurturant behaviour towards the young of non-human species may be a general human trait since it is practiced in a wide variety of cultures, including hunter-gatherers, and may arise from the merging of natural history and social intelligences that the archaeologist Steven Mithen suggests evolved ~100,000 years before present (YBP). The visual stimuli that evoke such nurturant behaviour, Lorenz's ‘Kindschenschema’, or ‘cuteness’, have been compared with the super-stimuli whereby parasitic cuckoos induce care-giving from their hosts, but recent evidence suggests that human females of childbearing age are especially sensitised to respond most strongly to characteristics of human infants, and may correspondingly become less attracted towards ‘cute’ animals. It is also possible that during human prehistory, the ability to care for young animals was selected for, in adolescent females, as an honest indicator of future quality as a mother. An ability to empathise with animals may also have given certain individuals and/or groups of kin an evolutionary advantage in hunting, and subsequently herding and domesticating, animals. Concern for animal welfare may therefore stem from an evolved human trait, even though its degree and extent of expression are undoubtedly strongly influenced by culture.

Effects of brain and facial size on basicranial form in human and primate evolution

Understanding variation in the basicranium is of central importance to paleoanthropology because of its fundamental structural role in skull development and evolution. Among primates, encephalisation is well known to be associated with flexion between midline basicranial elements, although it has been proposed that the size or shape of the face influences basicranial flexion. In particular, brain size and facial size are hypothesized to act as antagonists on basicranial flexion. One important and unresolved problem in hominin skull evolution is that large-brained Neanderthals and some Mid-Pleistocene humans have slightly less flexed basicrania than equally large-brained modern humans. To determine whether or not this is a consequence of differences in facial size, geometric morphometric methods were applied to a large comparative data set of non-human primates, hominin fossils, and humans (N = 142; 29 species). Multiple multivariate regression and thin plate spline analyses suggest that basicranial evolution is highly significantly influenced by both brain size and facial size. Increasing facial size rotates the basicranium away from the face and slightly increases the basicranial angle, whereas increasing brain size reduces the angles between the spheno-occipital clivus and the presphenoid plane, as well as between the latter and the cribriform plate. These interactions can explain why Neanderthals and some Mid-Pleistocene humans have less flexed cranial bases than modern humans, despite their relatively similar brain sizes. We highlight that, in addition to brain size (the prime factor implicated in basicranial evolution in Homo), facial size is an important influence on basicranial morphology and orientation. To better address the multifactorial nature of basicranial flexion, future studies should focus on the underlying factors influencing facial size evolution in hominins.

Malaria infection and the anthropological evolution

During the evolution of the genus Homo, with regard to species habilis, erectus and sapiens, malaria infection played a key biological role, influencing the anthropological development too. Plasmodia causing malaria developed two kinds of evolution, according to a biological and philogenetical point of view. In particular, Plasmodium vivax, Plasmodium malariae, and Plasmodium ovale, would have either coevolved with human mankind (coevolution), or reached human species during the most ancient phases of genus Homo evolution. On the other hand, Plasmodium falciparum has been transmitted to humans by monkeys in a more recent period, probably between the end of Mesolithic and the beginning of Neolithic age. The authors show both direct and indirect biomolecular evidences of malaria infection, detected in buried subjects, dating to the Ancient World, and brought to light in the course of archeological excavations in some relevant Mediterranean sites. In this literature review the Authors organize present scientific evidences: these confirm the malarial role in affecting the evolution of populations in Mediterranean countries. The people living in several different regions on the Mediterranean Sea sides, the cradle of western civilization, have been progressively influenced by malaria, in the course of the spread of this endemic disease during the last millennia. In addition, populations affected by endemic malaria developed cultural, dietary and behaviour adaptations, contributing to decrease the risk of disease. These habits were not probably fully conscious. Nevertheless it may be thought that both these customs and biological modifications, caused by malarial plasmodia, favoured the emergence of groups of people with a greater resistance against malaria. All these considered factors decreased demographical impact, influencing in a favourable way the general development and growth of civilization.

Cranial morphology of Javanese Homo erectus: New evidence for continuous evolution, specialization, and terminal extinction

Our current knowledge of the evolution of Homo during the early to middle Pleistocene is far from complete. This is not only because of the small number of fossil samples available, but also due to the scarcity of standardized datasets which are reliable in terms of landmark identification, interobserver error, and other distorting factors. This study aims to accurately describe the cranial morphological changes of H. erectus in Java using a standardized set of measurements taken by the authors from 18 adult crania from Sangiran, Trinil, Sambungmacan, and Ngandong. The identification of some obscure landmarks was aided by the use of micro-CT imaging. While recent studies tend to emphasize evolutionary conservatism in Javanese H. erectus, our results reinforce the theory that chronologically later groups experienced distinct morphological changes in a number of cranial traits. Some of these changes, particularly those related to brain size expansion, are similar to those observed for the genus Homo as a whole, whereas others are apparently unique specializations restricted to Javanese H. erectus. Such morphological specializations in Java include previously undescribed anteroposterior lengthening of the midcranial base and an anterior shift of the posterior temporal muscle, which might have influenced the morphology of the angular torus and supramastoid sulcus. Analyses of morphological variation indicate that the three crania from Sambungmacan variously fill the morphological gap between the chronologically earlier (Bapang-AG, Bapang Formation above the Grenzbank zone in Sangiran) and later (Ngandong) morphotypes of Java. At least one of the Bapang-AG crania, Sangiran 17, also exhibits a few characteristics which potentially indicate evolution toward the Ngandong condition. These strongly suggest the continuous, gradual morphological evolution of Javanese H. erectus from the Bapang-AG to Ngandong periods. The development of some unique features in later Javanese H. erectus supports the hypothesis that this Javanese lineage went extinct without making significant contributions to the ancestry of modern humans.

Cladistic analysis of continuous modularized traits provides phylogenetic signals in Homo evolution

Evolutionary novelties in the skeleton are usually expressed as changes in the timing of growth of features intrinsically integrated at different hierarchical levels of development. As a consequence, most of the shape-traits observed across species do vary quantitatively rather than qualitatively, in a multivariate space and in a modularized way. Because most phylogenetic analyses normally use discrete, hypothetically independent characters, previous attempts have disregarded the phylogenetic signals potentially enclosed in the shape of morphological structures. When analysing low taxonomic levels, where most variation is quantitative in nature, solving basic requirements like the choice of characters and the capacity of using continuous, integrated traits is of crucial importance in recovering wider phylogenetic information. This is particularly relevant when analysing extinct lineages, where available data are limited to fossilized structures. Here we show that when continuous, multivariant and modularized characters are treated as such, cladistic analysis successfully solves relationships among main Homo taxa. Our attempt is based on a combination of cladistics, evolutionary-development-derived selection of characters, and geometric morphometrics methods. In contrast with previous cladistic analyses of hominid phylogeny, our method accounts for the quantitative nature of the traits, and respects their morphological integration patterns. Because complex phenotypes are observable across different taxonomic groups and are potentially informative about phylogenetic relationships, future analyses should point strongly to the incorporation of these types of trait.