Précis of Evolution in Four Dimensions

In his theory of evolution, Darwin recognized that the conditions of life play a role in the generation of hereditary variations, as well as in their selection. However, as evolutionary theory was developed further, heredity became identified with genetics, and variation was seen in terms of combinations of randomly generated gene mutations. We argue that this view is now changing, because it is clear that a notion of hereditary variation that is based solely on randomly varying genes that are unaffected by developmental conditions is an inadequate basis for evolutionary theories. Such a view not only fails to provide satisfying explanations of many evolutionary phenomena, it also makes assumptions that are not consistent with the data that are emerging from disciplines ranging from molecular biology to cultural studies. These data show that the genome is far more responsive to the environment than previously thought, and that not all transmissible variation is underlain by genetic differences. In Evolution in Four Dimensions (2005) we identify four types of inheritance (genetic, epigenetic, behavioral, and symbol-based), each of which can provide variations on which natural selection will act. Some of these variations arise in response to developmental conditions, so there are Lamarckian aspects to evolution. We argue that a better insight into evolutionary processes will result from recognizing that transmitted variations that are not based on DNA differences have played a role. This is particularly true for understanding the evolution of human behavior, where all four dimensions of heredity have been important.     

Sexual promiscuity & self-control: A behavior genetic explanation to an evolutionary question

Within separate academic disciplines there exist two consistent findings that have emerged. Behavior geneticists, on one hand, continue to uncover moderate to high heritability estimates for virtually every human trait measurable. Evolutionary psychologists, on the other hand, have thoroughly documented species-wide universality in various human traits, suggesting that natural (or sexual) selection may have directly favored such outcomes. The goal of the current study, then, is to explore ways in which these lines of inquiry can be united via the use of behavior genetic methodologies coupled with evolutionary thought. Additionally, we attempt to unite our findings in a framework that can both account for the existence of heritable individual differences, while also understanding the importance of species-wide characteristics.     

Traits and trade-offs are an important tier

Replies to comments by K. M. Sheldon et al on the author's original article 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.     

On the Universality of Human Nature and the Uniqueness of the Individual: The Role of Genetics and Adaptation

The concept of a universal human nature, based on a species-typical collection of complex psychological adaptations, is defended as valid, despite the existence of substantial genetic variation that makes each human genetically and biochemically unique. These apparently contradictory facts can be reconciled by considering that (a) complex adaptations necessarily require many genes to regulate their development, and (b) sexual recombination makes it improbable that all the necessary genes for a complex adaptation would be together at once in the same individual, if genes coding for complex adaptations varied substantially between individuals. Selection, interacting with sexual recombination, tends to impose relative uniformity at the functional level in complex adaptive designs, suggesting that most heritable psychological differences are not themselves likely to be complex psychological adaptations. Instead, they are mostly evolutionary by-products, such as concomitants of parasite-driven selection for biochemical individuality. An evolutionary approach to psychological variation reconceptualizes traits as either the output of species-typical, adaptively designed development and psychological mechanisms, or as the result of genetic noise creating perturbations in these mechanisms.     

The extraversion continuum in evolutionary perspective: A review of recent theory and evidence

We review research on the ultimate and proximate origins of variation along the extraversion continuum. After describing the cost-benefit tradeoffs that may have maintained variation in extraversion over human evolution, we consider the evidence bearing on multiple distinct evolutionary hypotheses regarding the causal underpinnings of such variation. On the basis of the reviewed evidence, we argue that fluctuating selection on specific polymorphic genotypes is unlikely to explain the origins of individual differences in extraversion. Rather, adaptively patterned variation in extraversion is likely orchestrated primarily by facultative adaptations designed to calibrate behavioral strategies to cues available in ontogeny. For example, emerging research supports the hypothesis that extraversion may be “reactively heritable” by virtue of its calibration to heritable condition-dependent phenotypic features – which in turn helps explain extraversion’s genetic variance, as well as its consistent positive association with reproductive success. Finally, evidence suggests that some of the inter-individual variance in extraversion is fundamentally noisy, arising as a side effect of mutation–selection balance or pleiotropic polymorphisms maintained via pathogen–host coevolution. If correct, these conclusions indicate that future research should focus on elucidating the facultative adaptations designed to regulate the production of behaviors falling on the extraversion continuum.     

Entrepreneurs and evolutionary biology: The relationship between testosterone and new venture creation

Biological evolutionary processes select for heritable behaviors providing a survival and reproductive advantage. Accordingly, how we behave is, at least in part, affected by the evolutionary history of our species. This research uses evolutionary psychology as the theoretical perspective for exploring the relationship between a heritable biological characteristic (testosterone level) and an important business behavior (new venture creation). Data were collected from 31 MBA students with significant prior involvement in new venture creation and from 79 other student subjects with no new venture start-up experience. Consistent with evolutionary psychological theory, the biological (testosterone level) effect upon behavior (new venture creation) is partially mediated by the psychological (risk propensity).     

Behavioral genetic variation, adaptation and maladaptation: an evolutionary perspective

Evolutionary psychology seeks to understand the adaptive, evolved nature of humans by considering the forces of natural selection that gave rise to it. Individual humans also exhibit maladaptation, however, and some of the variation in maladaptive conditions is heritable. An evolutionary perspective can shed light on these phenomena too. Recent work suggests that developmental imprecision importantly affects the fitness of organisms and some of the genetic influences have been identified. Both theory and evidence that developmental imprecision underlies human cognitive maladaptation has begun to accumulate, although the manner in which the developing brain is affected remains largely unknown.     

Genetic influences on language impairment and phonological short-term memory

It has been known for some years that specific language impairment (SLI), an unexpected failure to acquire age-appropriate language skills, is highly heritable. However, molecular genetic studies have been hampered by the heterogeneity of the disorder and the predominant lack of clear genotype-phenotype relationships. We review recent studies suggesting that a better understanding of the genetics of SLI might emerge if we move away from clinical criteria for diagnosis to look instead at a theoretically based quantitative and cognitive measure of the phenotype: a test of phonological short-term memory (STM). Deficient phonological STM has been linked to specific genetic loci, and might play a role in determining some types of reading impairment as well as SLI. Identifying those cognitive deficits that work best as indices of heritable phenotypes will help us to uncover the aetiology of developmental disorders.     

Biological preparedness and evolutionary explanation

It is commonly supposed that evolutionary explanations of cognitive phenomena involve the assumption that the capacities to be explained are both innate and modular. This is understandable: independent selection of a trait requires that it be both heritable and largely decoupled from other 'nearby' traits. Cognitive capacities realized as innate modules would certainly satisfy these contraints. A viable evolutionary cognitive psychology, however, requires neither extreme nativism nor modularity, though it is consistent with both. In this paper, we seek to show that rather weak assumptions about innateness and modularity are consistent with evolutionary explanations of cognitive capacities. Evolutionary pressures can affect the degree to which the development of a capacity is canalized by biasing acquisition/learning in ways that favor development of concepts and capacities that proved adaptive to an organism's ancestors.     

An evolutionary hypothesis of suicide: why it could be biologically adaptive and is so prevalent in certain occupations

From an evolutionary perspective, suicide is a puzzle, because it has serious adverse effects, yet is remarkably common and heritable. An hypothesis is proposed to explain this puzzle, by explaining how suicide could be adaptive through reducing risk that individuals will transmit infections to kin. Empirical evidence supports four predictions from the hypothesis. There are well-established mechanisms by which infections and immune factors increase risk for mental disorders that contribute to suicide. Suicide is more prevalent in occupations with greater exposure to infection and immune-compromising factors and at higher latitudes, where key environmental factors increase vulnerability to infection. In several other highly social species, suicide-like behaviors have evolved to reduce transmission of infections. If the hypothesis is correct, detection and treatment of underlying infections and immune dysfunction should help predict and prevent suicidal behavior, while also combating spread of infectious diseases.     

Do individual differences in sociosexuality represent genetic or environmentally contingent strategies? Evidence from the Australian twin registry

Although men are substantially more interested than women in casual sex, there is ample variation in this trait (sociosexuality) within both sexes. One theory hypothesizes that within-sex sociosexual variation results from genetic variation maintained by frequency-dependent selection. If so, sociosexuality should be substantially heritable. A competing theory is that children acquire their mating strategy after observing their parents' relationship. By this theory, sociosexuality should reveal a strong shared environmental component. The authors studied genetic and environmental influences on sociosexuality using a large, representative volunteer twin sample. Parental marital instability was modestly associated with sociosexuality, but this could have been due to either genetic or environmental factors. Consistent with genetic theory, familial resemblance appeared primarily due to additive genetic rather than shared environmental factors.     

论进化心理学的“心理机制”

“心理机制”是进化心理学的核心概念。对这一概念的理解直接影响着对整个进化心理学理论的理解。该文尝试从心理学其它相关学科的角度,对这一概念的性质进行充分的解读与分析,同时也指出进化心理学“心理机制”理论之明显误区,并在此基础上对进化心理学价值之所在给予充分的彰显。     

The Anthropocentric Predicament and the Search for Extra-terrestrial Intelligence (The Universe as Seen Through Our Eyes Darkly)

Concepts from evolutionary biology are conjoined with a Kantian- and Nietzschian-based critique to demonstrate that our human concepts and perspectives are hopelessly 'earthbound.' Unless the caprice of evolutionary biology on some Earth-like planet replicates the evolutionary history of Earth, we shall not recognise alien intelligence. To suggest that another planet is likely to produce a recognisable intelligence because its evolutionary history is similar to ours is simply absurd, but will seem absurd only to those with a knowledge of bio-evolution, an understanding of our linguistic and syntactical abilities, and concepts of space, time, and causality. This conclusion may appear heavy-handed, even pedestrian. However, a closer scrutiny reveals that it is the search for extra-terrestrial intelligence which is naive.     

Social-relational exposures and well-being: Using multivariate twin data to rule-out heritable and shared environmental confounds

The aims of the present study were as follows: (1) Using a large sample of adults, estimate overlap between social-relational exposures measured at midlife and well-being measured at midlife and approximately 9-years later. (2) Using a subsample of twins, test for heritable variation in social-relational exposures, and (3) controlling for heritable and shared environmental variation, estimate overlap between social-relational exposures and well-being, both concurrently and approximately 9-years later. Results indicated small-to-moderate overlap between exposures and well-being (mean r = 0.29, range = 0.05–0.54). There was also evidence for heritable variation in exposures, and after accounting for these genetic factors, the degree of overlap between social-relational exposures and well-being decreased (mean r = 0.10, range = −0.07 to 0.33).     

Genetic Support for the Dual Nature of Attention Deficit Hyperactivity Disorder: Substantial Genetic Overlap Between the Inattentive and Hyperactive–impulsive Components

Objective Attention deficit hyperactivity disorder (ADHD) is a common, complex and highly heritable disorder, characterised by inattentive, impulsive and overactive behaviour. Evidence for the heritability of ADHD measures in twin population samples has come from the analysis of total scores that combine inattentive and hyperactive–impulsive symptoms subscales. This study investigated, in a community sample, the aetiology of ADHD-like traits and the aetiological overlap between the two dimensions that define the ADHD disorder. Materials and Methods Parents of 6,222 approximately 8-year-old twin pairs from the Twins Early Development Study (TEDS) population sample completed the two subscales of the Conners’ 18-item DSMIV checklist, a screening instrument for ADHD symptoms. Results Both subscales were highly heritable (hyperactive–impulsive: 88%; inattentive: 79%). Bivariate genetic modelling indicated substantial genetic overlap between the two components; however, there were significant independent genetic effects. Conclusions These findings suggest that many genes associated with the hyperactivity–impulsivity dimension will also be associated with the inattentive dimension but that there is significant genetic heterogeneity as well. These results provide genetic support for combining the two behavioural dimensions that define ADHD, but also suggest that some symptom-specific genes will also be identified. Correspondence and reprint requests to Gráinne McLoughlin, SGDP Centre, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, Tel: +44(0) 207-848-5261; Email: g.mcloughlin@iop.kcl.ac.uk.     

Socio-demographic factors intensifying male mating competition exacerbate male mortality rates

Sex differences in mortality rates stem from a complex set of genetic, physiological, psychological, and social causes whose influences and interconnections are best understood in an integrative evolutionary life history framework. Although there are multiple levels of mechanisms contributing to sex based disparities in mortality rates, the intensity of male mating competition in a population may have a crucial role in shaping the level of excess male mortality. The degree of variation and skew in male reproductive success may shape the intensity of male mating competition, leading to riskier behavioral and physiological strategies. This study examines three socio-demographic factors related to variation in human male reproductive success; polygyny, economic inequality, and the population ratio of reproductively viable men to women across nations with available data. The degrees of economic inequality and polygyny explained unique portions in the sex difference in mortality rates, these predictors accounted for 53% of the variance. The population ratio of reproductively viable men to women did not explain any additional variance. These results demonstrate the association between social conditions and health outcomes in modern nations, as well as the power of an evolutionary life history framework for understanding important social issues.     

The genetics of dietary experience in a restricted natural population

The sources of individual differences in human and nonhuman animals remain controversial. We demonstrate that diet and genetics interact in determining the ontogenetic trajectory of chemosensory and prey preferences in the common garter snake, Thamnophis sirtalis , a dietary generalist. In litters of neonate snakes from a single small field in an earthworm-ingesting population, initial responses to chemical cues from fish and worm were similar, with zero heritabilities. After 12 meals on fish, however, the heritability of both fish and worm chemosensory responses increased markedly, the change in response to fish but not worm chemicals was heritable, the relative preference for fish versus worm was heritable, and the change in relative preference was heritable. In addition, growth rates on each diet were related to changes in chemoreceptive responses. Such genetic-environment variation that emerges only after equivalent ontogenetic experience may be a factor in responses to environmental change in many species.