Sphenoid shortening and the evolution of modern human cranial shape

Crania of 'anatomically modern' Homo sapiens from the Holocene and Upper Pleistocene epochs differ from those of other Homo taxa, including Neanderthals, by only a few features. These include a globular braincase, a vertical forehead, a dimunitive browridge, a canine fossa and a pronounced chin. Humans are also unique among mammals in lacking facial projection: the face of the adult H. sapiens lies almost entirely beneath the anterior cranial fossa, whereas the face in all other adult mammals, including Neanderthals, projects to some extent in front of the braincase. Here I use radiographs and computed tomography to show that many of these unique human features stem partly from a single, ontogenetically early reduction in the length of the sphenoid, the central bone of the cranial base from which the face grows forward. Sphenoid reduction, through its effects on facial projection and cranial shape, may account for the apparently rapid evolution of modern human cranial form, and suggests that Neanderthals and other archaic Homo should be excluded from H. sapiens.     

On the confusion of "race" with biophysical diversity.

Responds to M. J. Zyphur's (see record 2006-01690-012) comments on the original article by A. Smedley and B. D. Smedley (see record 2005-00117-003). Race, as people live and understand it, inhabits a dimension of reality that transcends biology and cannot be reduced to genes, chromosomes, or even phenotypes. A biological or genetic view of race cannot encompass the lived social reality of race, nor does it represent biogenetic variations in human populations very well (Marks, 1995). As Zyphur notes, biogenetic variations in the human species were produced by evolutionary forces as different groups interacted with and underwent adaptation to the natural environments encountered in their migrations. The result was a pattern of variation that should be familiar to everyone: People with dark skin coloring remained adapted to tropical environments (with some internal variations resulting from amounts of tree cover, land elevation, rainfall, etc.). Peoples of tropical lands thus resemble one another in their varying shades of dark skin color and often curly or frizzy hair (known as polytopicity). Some of the darkest skins are found not in Africa but in India, Sri Lanka, Melanesia, and Northern Australia, as anyone who watched the news coverage of the recent tsunami would readily recognize. Groups migrating beyond the tropical areas gradually lost genes for dark skin as they adapted to cooler climates with less sunlight. Geneticists have shown that just as no two individuals are genetically alike (except for identical twins), no two human groups are precisely alike, even when they derive from a common ancestral population. Biogenetic variation has continued to increase as individuals once widely separated meet and mate. Quite apart from the controversy over races as biological taxa, the idea of race as it is known and lived in American society is composed of social values and meanings imposed on this biological variation over the past three or four centuries. As a social construct, race refers to an ideology. Since the 18th century, Americans and many other people in the world have been conditioned to believe that race as biology is the main source of human identities. As Americans have come into contact with peoples around the world, confusion has inevitably ensued, because U.S. racial categories do not necessarily apply in other countries. Given the complexity of the human genome and the history of (continuous) intermixtures, I doubt if it will ever be possible to correlate our genes with our racial (i.e., social) identities. Nor can I imagine at this point why anyone should want to do so. What service to society or science will this fulfill? Social constructs have their own complex dynamics and are vulnerable to change, just as is any other cultural phenomenon. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The SCL-90 factor structure in comorbid substance abusers

Studying the evolution of nesting behavior within the human-chimpanzee clade is problematic because evidence is sparse and difficult to interpret. Lacking a fossil or archaeological record for proto-chimpanzees, reconstructions of the antecedents of modern chimp nesting patterns can be reconstructed only from careful studies of variation in current chimpanzee and bonobo nesting patterns within the context of spatial and temporal landscape parameters. The ethology of nesting also provides an important frame of reference for reconstructions of early hominid nesting behavior. If the contemporary contrast between human and chimpanzee nesting patterns is seen as an evolutionary dichotomy, then African prehistoric landmarks that mark the origin of this split might include bipedalism and the origins of the hominidae, the first stone tools and the origins of Homo, the developmental and behavioral adaptations of Homo ergaster, shifts in Late Acheulian settlement patterns, and the origins of anatomically modern humans and the Middle Stone Age. The issue of whether Early Stone Age archaeological sites were used for nesting is unresolved because potential markers of such behavior, such as hearths, structures, or bedding, are not unambiguously recognizable in the archaeological record until the Middle Stone Age.     

Traits and trade-offs are insufficient for evolutionary personality psychology.

Comments on the article by D. Nettle (see record 2006-11202-005), who has clearly shown that evolutionary psychologists need to focus more attention on individual differences, not just species-typical universals. Such differences are not mere "noise," and evolutionary theory will gain by understanding how they are produced and maintained. However, by focusing on personality traits and the five-factor personality model, Nettle left unaddressed many of the most important aspects of human personality. An evolutionary psychology of personality must ultimately explain not just trait differences but also differences in personal goals, values, motives, identities, and life narratives--essential elements of human individuality and functionality. K. M. Sheldon et al suggest four reasons why traits and the five-factor personality model do not provide an optimal approach for explaining the evolution of personality: (a) As constructs, traits provide little purchase for explaining the causes of behavior; (b) trait concepts do not acknowledge or explain people's variations around their own baselines, variations that are likely crucial for adaptation; (c) traits do not explain or even describe true human uniqueness, i.e. the ways in which a person is different from everybody else; and (d) traits do not explain personality from the inside, by considering what people are trying to do in their lives. In raising these issues Sheldon et al are suggesting that the important question for evolutionary personality study is not why people fall at different points on a continuum regarding traits x, y, and z, but rather why each person is inevitably unique while still sharing the same evolved psychology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Review of Genes, genesis, and God: Values and their origins in natural and human history.

Reviews the book, Genes, genesis, and God: Values and their origins in natural and human history by Holmes Rolston III (1999). Drawn from a series of lectures given by the author in November of 1997 at the University of Edinburgh as part of the Gifford Lectures, this book addresses the question of whether the supremely social and human phenomena of religion and ethics can be ultimately reduced to the phenomena of biology. Challenging much of what passes for unassailable truth in sociobiological and similar natural science circles, Rolston argues that religion, ethics, and science—as emergent phenomena in human culture—are not only crowning and distinctive achievements in human cultural history but that it is impossible to adequately conceive of them as having resulted from simple evolutionary or biological processes. To this end, the author argues that genetic and evolutionary processes are anything but blind, selfish, and contingent. Indeed, Rolston cogently argues that not only are our sciences of nature not value free, but nature itself is laden with values. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Middle Pleistocene human tibia from Boxgrove

The Boxgrove tibia was discovered in 1993, associated with Middle Pleistocene fauna, and Lower Palaeolithic archaeology. The sediments at Boxgrove were deposited during a temperate interglacial episode and ensuing cold stage. They thus represent a wide range of modes and environments of deposition. Archaeological remains have been excavated from all the major stratigraphic units, giving a continuity of occupation for this part of southern England over a 10(4) year timescale, through markedly changing climatic regimes. The stratigraphic, archaeological and sedimentological contexts of the tibia are described, as well as its preservation and morphology. Measurements are given, with discussion of reconstructed bone length, and stature estimates. Comparative measurements are provided for fossil and recent human samples: the large dimensions of its diaphysis place the Boxgrove tibia near or beyond the upper size limits of the comparative samples, but its reconstructed length and estimated stature are less exceptional. The elevated robusticity of the specimen indicates exceptional diaphyseal strength and/or cold adapted body proportions paralleling those of the Neanderthals. Disagreement about the taxonomy of Middle Pleistocene hominids and lack of comparable fossil material make a specific assignment for the Boxgrove tibia problematic. The tibia can only definitely be assigned to non-modern Homo sp., with possible further reference to Homo cf. heidelbergensis (Schoetensack, 1908) on temporal and geographic grounds, if the validity of that species is accepted.     

Beyond the pleistocene: Using phylogeny and constraint to inform the evolutionary psychology of human mating.

Evolutionary psychologists explore the adaptive function of traits and behaviors that characterize modern Homo sapiens. However, evolutionary psychologists have yet to incorporate the phylogenetic relationship between modern Homo sapiens and humans’ hominid and pongid relatives (both living and extinct) into their theorizing. By considering the specific timing of evolutionary events and the role of evolutionary constraint, researchers using the phylogenetic approach can generate new predictions regarding mating phenomena and derive new explanations for existing evolutionary psychological findings. Especially useful is the concept of the adaptive workaround—an adaptation that manages the maladaptive elements of a pre-existing evolutionary constraint. The current review organizes 7 features of human mating into their phylogenetic context and presents evidence that 2 adaptive workarounds played a critical role as Homo sapiens’s mating psychology evolved. These adaptive workarounds function in part to mute or refocus the effects of older, previously evolved adaptations and highlight the layered nature of humans’ mating psychology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

In praise of brilliance: Where that praise really belongs.

Comments on the article by R. L. Hagen (see record 1997-02239-002) praising the null hypothesis statistical test. In sum, Hagen argued that "it is unlikely that we will ever be able to divorce ourselves from that [statistical test] logic even if someday we decide we want to". However, notwithstanding this representation, psychology can alter its behavior if psychologists deem such changes prudent and wise. If it is decided that statistical tests do not evaluate either result importance or result replicability, psychologists can report information that is relevant to these 2 concerns. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Traits and trade-offs are an important tier.

Replies to comments by K. M. Sheldon et al (see record 2007-18356-014) on the author's original article (see record 2006-11202-005) on evolution and personality variation. Sheldon et al concurred with the thrust of that article that the way natural selection shapes or gives rise to interindividual variation is a worthy topic for evolutionary psychologists to consider, so at a broad level Sheldon et al and Nettle are in agreement. The contention concerns the utility of broad traits such as the Big Five personality factors in undertaking evolutionary personality psychology. Nettle does not concur that traits do not provide a good approach to understanding interindividual variation. They have proved their utility in humans and in other species. Nettle does agree that traits alone are not sufficient for understanding personality functioning, particularly in humans, and hopes that other psychologists, including perhaps Sheldon et al, will add an evolution-informed understanding of those higher tiers of personality to the framework Nettle has suggested for the base tier. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extinction and the loss of evolutionary history

Extinction episodes, such as the anthropogenic one currently under way, result in a pruned tree of life. But what fraction of the underlying evolutionary history survives when k of n species in a taxon are lost? This is relevant both to how species loss has translated into a loss of evolutionary history and to assigning conservation priorities. Here it is shown that approximately 80 percent of the underlying tree of life can survive even when approximately 95 percent of species are lost, and that algorithms that maximize the amount of evolutionary history preserved are not much better than choosing the survivors at random. Given the political, economic, and social realities constraining conservation biology, these findings may be helpful.     

Review of Humor: The psychology of living buoyantly.

Reviews the book, Humor: The psychology of living buoyantly by Herbert M. Lefcourt (see record 2000-14400-000). Lefcourt traces the changing concerns of psychology, and the reason why the psychological study of humour has often been trivialized as an unlikely candidate for research support in the past. The author charts his own personal odyssey in the field, one in which he is drawn to the study of human strengths rather than human frailties. An early chapter sets us up for the remaining chapters by reminding us how we experience humour in everyday life. Verbatim anecdotes from students in previous seminars offer vignettes which allow the reader to grasp the situation vicariously and to see how and why the humour of the situation could have arisen. It is here that Lefcourt confides that his is a functionalist psychological perspective, and that he views humour as a characteristic that has been useful to our species. Here one comes to the crux of the argument for most readers. Is humour, then, a coping strategy, ultimately devised in our evolutionary ramblings, as a protective cushion against the jagged impact of stressful experiences? The middle part of this book explores this hypothesis in a variety of experimental settings, all designed to assess the moderating role of humour in the face of stress. This is a useful, even uplifting, book about the human search for emotional well-being. Its academic value in outlining the history and current thrust of work in the field of humour is obvious, but this reviewer appreciated its bold attempt to provide a more personal view of human adaptation to life's stressful requirements. Very simply, this is a book that resonates with one's understanding of life beyond the research laboratory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experimental investigations of species-specific behavior.

"I have come to question the logical defensibility of any concept of a comparative psychology. My doubts stem in part from the conviction that Homo sapiens is, in some ways, a truly unique species." A highly developed learning capacity is a distinctive characteristic of the human species. 2 desiderata seem obvious to build a "comparative science of behavior": (a) behavior selected for examination should be "natural" to the species and (b) the kinds of behavior chosen for analysis should be as widely distributed as possible, phylogenetically speaking. Major headings are: Species-Specific Behavior, Plan of Attack, Determinants of Behavior (Historical Determinants, Indirect Environmental Determinants, Direct Environmental Determinants, Organismic Determinants), and Conclusions. The proposed "broadening of our orientation would facilitate and encourage rich interspecific comparisons and thus give rise to a truly comparative body of knowledge pertaining to behavior." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relationship imperative: Arguments for a broad definition of attachment.

S. Goldberg, J. E. Grusec, and J. M. Jenkins (see record 1999-15264-001) argued that an evolutionary model restricted to the protective function of parent–infant relationships provides a distinctive focus for attachment theory. An alternative model that assumes that the evolutionary advantage of the attachment system is based on the imperative that parents and infants develop a stable relationship may be more consistent with modern evolutionary theory as well as current advances in attachment research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oversimplifying evolutionary psychology leads to explanatory gaps.

Comments on Evolutionary psychology: Controversies, questions, prospects, and limitations (see record 2010-02208-001) by Confer et al. They argued that SST cannot explain the existence of either homosexuality or suicide within the human species. We contend that a sufficiently nuanced evolutionary position has no difficulties explaining either phenomenon. Also in this account, it is assumed that all psychological functioning must serve survival and reproduction. However, since evolution selects against certain qualities (it does not select for qualities, as it is commonly, but incorrectly, described), two types of qualities should remain intact for any species: (a) those that facilitate survival and reproduction and (b) those that do not impede survival and reproduction at the population level. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The correlation of the ecological niches of the common (Rana temporaria L.) and of the moor (Rana arvalis Nilss.) frogs (Anura, Amphibia)]

During 25 years ecology and population dynamic of two brown frog species (Rana temporaria and R. arvalis) were studied in Moscow region, Solovki island and South Ural. We compared life cycles characteristics, namely biotope preferences, diet, migration, enemies, hibernation places using own and available literature data. Then we analyse how these parameters are changed among the species area and ecological niches were compared. We found that these two species do not compete in any stage of life cycle. Ecological niches are very closed and differences are determined generally by abiotic factors. So, R. temporaria prefers more wet biotope and more sensitive to acidity (low pH value). Differences in spawning time do not associate with interference in spawning places. We conclude that interspecific competition did not take place neither in the past nor in present and the reason of differences in ecological niches are determined by separate ways of evolutionary development of these species.     

Differences between chimpanzees (Pan troglodytes) and humans (Homo sapiens) in the resting state of the index finger: Implications for pointing.

Pointing with the index finger is a universal human (Homo sapiens) behavior found in cultures around the world. The emergence of pointing in infancy has traditionally been linked with the early development of cognitive capacities such as perspective-taking, intersubjectivity, and empathy. In contrast to humans, chimpanzees (Pan troglodytes) do not develop a pointing gesture with the index finger and rarely point by gesturing with hands or arms. However, recent experimental data suggest that chimpanzees may develop cognitive skills related to perspective-taking and empathy. In this article we report the existence of a difference in the resting morphology of the index finger in humans and chimpanzees. We speculate on how this species difference may be related to species differences in pointing with the index finger. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Dog's Got Personality: A Cross-Species Comparative Approach to Personality Judgments in Dogs and Humans.

This research offers a blueprint for how a cross-species comparative approach can be realized empirically. In a single design, parallel procedures and instruments were used in 2 species, dogs (Canis familiaris) and humans (Homo sapiens), to test whether personality differences exist and can be judged in dogs as accurately as in humans. Personality judgments of humans and dogs were compared on 3 accuracy criteria: internal consistency, consensus, and correspondence. Results showed that, on all 3 criteria, judgments of dogs were as accurate as judgments of humans. These findings are consistent with the evolutionary continuity hypothesis and suggest an important conclusion not widely considered by either personality or animal researchers: Personality differences do exist and can be measured in animals other than humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparative mtDNA phylogeography of neotropical freshwater fishes: testing shared history to infer the evolutionary landscape of lower Central America

Historical biogeography seeks to explain contemporary distributions of taxa in the context of intrinsic biological and extrinsic geological and climatic factors. To decipher the relative importance of biological characteristics vs. environmental conditions, it is necessary to ask whether groups of taxa with similar distributions share the same history of diversification. Because all of the taxa will have shared the same climatic and geological history, evidence of shared history across multiple species provides an estimate of the role of extrinsic factors in shaping contemporary biogeographic patterns. Similarly, differences in the records of evolutionary history across species will probably be signatures of biological differences. In this study, we focus on inferring the evolutionary history for geographical populations and closely related species representing three genera of primary freshwater fishes that are widely distributed in lower Central America (LCA) and northwestern Colombia. Analysis of mitochondrial gene trees provides the opportunity for robust tests of shared history across taxa. Moreover, because mtDNA permits inference of the temporal scale of diversification we can test hypotheses regarding the chronological development of the Isthmian corridor linking North and South America. We have focused attention on two issues. First, we show that many of the distinct populations of LCA fishes diverged in a relatively brief period of time thus limiting the phylogenetic signal available for tests of shared history. Second, our results provide reduced evidence of shared history when all drainages are included in the analysis because of inferred dispersion events that obscure the evolutionary history among drainage basins. When we restrict the analysis to areas that harbour endemic mitochondrial lineages, there is evidence of shared history across taxa. We hypothesize that there were two to three distinct waves of invasion into LCA from putative source populations in northwestern Colombia. The first probably happened in the late Miocene, prior to the final emergence of the Isthmus in the mid-Pliocene; the second was probably coincident with the rise of the Isthmus in the mid-Pliocene, and the third event occurred more recently, perhaps in the Pleistocene. In each case the geographical scale of the dispersion of lineages was progressively more limited, a pattern we attribute to the continuing development of the landscape due to orogeny and the consequent increase in the insularization of drainage basins. Thus, the fisheye view of LCA suggests a complex biogeographic history of overlaid cycles of colonization, diversification, sorting and extinction of lineages.