Cultural transmission can inhibit the evolution of altruistic helping

The study of culturally inherited traits has led to the suggestion that the evolution of helping behaviors is more likely with cultural transmission than without. Here we evaluate this idea through a comparative analysis of selection on helping under both genetic and cultural inheritance. We develop two simple models for the evolution of helping through cultural group selection: one in which selection on the trait depends solely on Darwinian fitness effects and one in which selection is driven by nonreproductive factors, specifically imitation of strategies achieving higher payoffs. We show that when cultural variants affect Darwinian fitness, the selection pressure on helping can be markedly increased relative to that under genetic transmission. By contrast, when variants are driven by nonreproductive factors, the selection pressure on helping may be reduced relative to that under genetic inheritance. This occurs because, unlike biological offspring, the spread of cultural variants from one group to another through imitation does not reduce the number of these variants in the source group. As a consequence, there is increased within-group competition associated with traits increasing group productivity, which reduces the benefits of helping. In these cases, selection for harming behavior (decreasing the payoff to neighbors) may occur rather than selection for helping.     

Patterns and Processes in Cultural Evolution

Darwinian models of cultural change have been motivated, in part, by the desire to provide a framework for the unification of the biological and the human sciences. In this paper, drawing upon a distinction between the evolution of enabling mechanisms for the acquisition and dissemination of knowledge (EEM) and the evolution of epistemic theses as cultural products (EET), we propose a model of how culture emerges as a product of biological evolution on the basis of the concept of reaction norms. The goal of this model is to provide a means for conceptualizing how the biological and the cultural realms are connected, when they start to disconnect, and what the key transitions are. We then assess the viability of a Darwinian approach to cultural change. We conclude that the prospects of producing a Darwinian model of cultural change that unifies the human sciences in a way that mirrors the unification of the biological sciences in the light of Darwin’s theory are rather dim.     

The potential significance of adaptive evolution and dimerization in chimpanzee intercellular cell adhesion molecules (ICAMs)

Cell adhesion molecules are involved in a diverse array of cellular processes. Recent data suggests that human immunodeficiency virus (HIV-1) co-opts their functions, in particular the properties of the intercellular cell adhesion molecules (ICAMs), to enhance viral infection and transmission. To investigate mechanisms that may underlie the non-progression that occurs in immunodeficiency virus-infected chimpanzees, we amplified the protein coding regions of multiple non-human primate ICAMs 1-5 and two ICAM ligands, leukocyte function-associated antigen-1 (LFA-1) and macrophage antigen 1 (Mac-1). We then employed a phylogenetic tree-based approach to comparative genomics, in order to screen for the presence of adaptive changes. Strong Darwinian positive selection in chimpanzee ICAMs 1, 2 and 3 was observed, most markedly in domains that are critical for the integrity and maintenance of ICAM-1 dimerization. As binding of ligands, including the attachment of virions, is influenced by the state of ICAM 1 dimerization, chimpanzee ICAMs may have evolved to modulate their own dimerization. In concert with previous evidence suggesting an ancient retroviral pandemic as a prominent selective force in chimpanzee evolution, adaptation of chimpanzee ICAMs may have effected a mechanism that explains the lack of immunosuppression observed following HIV-1 or simian immunodeficiency virus (SIVcpz) infection.     

SARS-CoV Genome Polymorphism： A Bioinformatics Study

A dataset of 103 SARS-CoV isolates （101 human patients and 2 palm civets） was investigated on different aspects of genome polymorphism and isolate classification. The number and the distribution of single nucleotide variations （SNVs） and insertions and deletions, with respect to a “profile”, were determined and discussed （“profile” being a sequence containing the most represented letter per position）. Distribution of substitution categories per codon positions, as well as synonymous and non-synonymous substitutions in coding regions of annotated isolates, was determined, along with amino acid （a.a.） property changes. Similar analysis was performed for the spike （S） protein in all the isolates （55 of them being predicted for the first time）. The ratio Ka/Ks confirmed that the S gene was subjected to the Darwinian selection during virus transmission from animals to humans. Isolates from the dataset were classified according to genome polymorphism and genotypes. Genome polymorphism yields to two groups, one with a small number of SNVs and another with a large number of SNVs, with up to four subgroups with respect to insertions and deletions. We identified three basic nine-locus genotypes： TTTT/TTCGG, CGCC/TTCAT, and TGCC/TTCGT, with four subgenotypes. Both classifications proposed are in accordance with the new insights into possible epidemiological spread, both in space and time.     

PERSPECTIVE: IS HUMAN CULTURAL EVOLUTION DARWINIAN? EVIDENCE REVIEWED FROM THE PERSPECTIVE OF THE ORIGIN OF SPECIES

The claim that human culture evolves through the differential adoption of cultural variants, in a manner analogous to the evolution of biological species, has been greeted with much resistance and confusion. Here we demonstrate that as compelling a case can now be made that cultural evolution has key Darwinian properties, as Darwin himself presented for biological evolution in The Origin of Species. Culture is shown to exhibit variation, competition, inheritance, and the accumulation of successive cultural modifications over time. Adaptation, convergence, and the loss or change of function can also be identified in culture. Just as Darwin knew nothing of genes or particulate inheritance, a case for Darwinian cultural evolution can be made irrespective of whether unitary cultural replicators exist or whether cultural transmission mechanisms are well understood.     

Rapid Evolution of the Ribonuclease A Superfamily: Adaptive Expansion of Independent Gene Clusters in Rats and Mice

The two eosinophil ribonucleases, eosinophil-derived neurotoxin (EDN/RNase 2) and eosinophil cationic protein (ECP/RNase 3), are among the most rapidly evolving coding sequences known among primates. The eight mouse genes identified as orthologs of EDN and ECP form a highly divergent, species-limited cluster. We present here the rat ribonuclease cluster, a group of eight distinct ribonuclease A superfamily genes that are more closely related to one another than they are to their murine counterparts. The existence of independent gene clusters suggests that numerous duplications and diversification events have occurred at these loci recently, sometime after the divergence of these two rodent species (∼10–15 million years ago). Nonsynonymous substitutions per site (d _N) calculated for the 64 mouse/rat gene pairs indicate that these ribonucleases are incorporating nonsilent mutations at accelerated rates, and comparisons of nonsynonymous to synonymous substitution (d _N / d _S) suggest that diversity in the mouse ribonuclease cluster is promoted by positive (Darwinian) selection. Although the pressures promoting similar but clearly independent styles of rapid diversification among these primate and rodent genes remain uncertain, our recent findings regarding the function of human EDN suggest a role for these ribonucleases in antiviral host defense. Received: 8 April 1999 / Accepted: 22 June 1999     

Molecular Evolution of CXCR1, a G Protein-Coupled Receptor Involved in Signal Transduction of Neutrophils

Human neutrophils are a type of white blood cell, which forms an early line of defense against bacterial infections. Neutrophils are highly responsive to the chemokine, interleukin-8 (IL-8) due to the abundant distribution of CXCR1, one of the IL-8 receptors on the neutrophil cell surface. As a member of the GPCR family, CXCR1 plays a crucial role in the IL-8 signal transduction pathway in neutrophils. We sequenced the complete coding region of the CXCR1 gene in worldwide human populations and five representative nonhuman primate species. Our results indicate accelerated protein evolution in the human lineage, which was likely caused by Darwinian positive selection. The sliding window analysis and the codon-based neutrality test identified signatures of positive selection at the N-terminal ligand/receptor recognition domain of human CXCR1. [Reviewing Editor: Dr. Manyuan Long] The GenBank accession numbers of sequences reported herein are AY916760–AY916773.     

Intrinsic noise and the design of the genetic machinery

Darwinian theory envisages 'selection pressure' as a stress imposed on the genotype by the environment. However, noise in the replicative and translational mechanisms in itself imposes a significant 'pressure' on the adaptive fitness of the organism. We propose that the biosphere has been shaped by both extrinsic (environmental) and intrinsic (noise-generated) factors. Because noise has been a remorseless and ever-present background to the evolutionary process, adaptations to this intrinsic pressure include not only a variety of familiar genetic mechanisms but also many anatomical and life-style characteristics that focus on the transmission of information between generations.     

A perspective on Darwinian psychology: The importance of domain-general mechanisms,plasticity, and individual differences

In this paper a theory of Darwinian psychological adaptations as motive dispositions with an affective core is developed, and it is argued that 1) there is significant plasticity in these mechanisms; 2) in addition to domain-specific evolved motive dispositions, there are a variety of domain-general cognitive and emotional mechanisms; 3) humans are capable of developing motive dispositions which are not adaptations; 4) the relationship between evolved motive dispositions and behavior is very tenuous so that the explanatory power of Darwinian psychology is very weak; 5) individual differences in human psychological characteristics are evolutionarily meaningful and are linked to mechanisms which assess the resource value of intraspecific genetic and phenotypic diversity.     

Clonal selection parallels between normal and cancer tissues

Clonal selection and drift drive both normal tissue and cancer development. However, the biological mechanisms and environmental conditions underpinning these processes remain to be elucidated. Clonal selection models are centered in Darwinian evolutionary theory, where some clones with the fittest features are selected and populate the tissue or tumor. We suggest that different subclasses of stem cells, each of which is responsible for a distinct feature of the selection process, share common features between normal and cancer conditions. While active stem cells populate the tissue, dormant cells account for tissue replenishment/regeneration in both normal and cancerous tissues. We also discuss potential mechanisms that drive clonal drift, their interactions with clonal selection, and their similarities during normal and cancer tissue development.     

Specific inactivation of inhibitory sequences in the 5' end of the human papillomavirus type 16 L1 open reading frame results in production of high levels of L1 protein in human epithelial cells

The expression of human papillomavirus type 16 late genes encoding virus capsid proteins L1 and L2 is restricted to terminally differentiated epithelial cells in the superficial layers of the squamous epithelium. We wish to understand the molecular mechanisms that determine the levels of expression of the human papillomavirus type 16 late genes. We have previously shown that the L1 coding region contains inhibitory sequences. Here we extend previous findings to show that the 5' end of the L1 gene contains strong inhibitory sequences but that the 3' end does not. We show that the first 514 nucleotides of the L1 coding region contain multiple inhibitory elements that act independently of one another and that the major inhibitory element is located within the first 129 nucleotides of the L1 gene. Introduction of point mutations in the inhibitory elements in the 5' end of the L1 gene which altered the RNA sequence without affecting the protein sequence specifically inactivated the inhibitory elements and resulted in production of high levels of human papillomavirus type 16 L1 mRNA and protein in human epithelial cells. Furthermore, we show that inhibitory sequences are present in the L1 coding regions of multiple human papillomavirus types, demonstrating that these elements are conserved among the human papillomaviruses, and suggest that they have an important function in the viral life cycle.     

Comprendre la dépression : apport de la psychologie évolutionniste

Darwinian medicine considers that many symptoms are the organism’s defence mechanisms and adaptations that have been inherited and shaped by natural selection. But in many cases, signs and symptoms of disease are of no benefit to human survival and are in fact deregulations of normal mechanisms. Evolutionary explanations help us understand how some human affective and emotional processes could have an adaptive value and enable us to cope with a wide spectrum of situations. But the wide range of intensity levels and different forms, ranging from low moods to major depression with psychotic features, suggest that these symptoms cannot always be explained by adaptation: where is the cut-off point? In this paper, we describe the evolutionary concepts related to adaptation as applied to the emotions, particularly focusing on low mood and depression, and discuss their possible functional and adaptive role.     

Saltational symbiosis

Symbiosis has long been associated with saltational evolutionary change in contradistinction to gradual Darwinian evolution based on gene mutations and recombination between individuals of a species, as well as with super-organismal views of the individual in contrast to the classical one-genome: one organism conception. Though they have often been dismissed, and overshadowed by Darwinian theory, suggestions that symbiosis and lateral gene transfer are fundamental mechanisms of evolutionary innovation are borne out today by molecular phylogenetic research. It is time to treat these processes as central principles of evolution.     

Donors to charity gain in both indirect reciprocity and political reputation

Darwinian evolution can explain human cooperative behaviour among non-kin by either direct or indirect reciprocity. In the latter case one does not expect a return for an altruistic act from the recipient as with direct reciprocity, but from another member of the social group. However, the widespread human behaviour of donating to poor people outside the social group, for example, to charity organizations, that are unlikely to reciprocate indirectly and thus are equivalent to defectors in the game is still an evolutionary puzzle. Here we show experimentally that donations made in public to a well-known relief organization resulted both in increased income (that the donors received from the members of their group) and in enhanced political reputation (they were elected to represent the interests of their group). Donations may thus function as an honest signal for one's social reliability.     

Nicotinic acetylcholine receptors: from structure to brain function

Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels and can be divided into two groups: muscle receptors, which are found at the skeletal neuromuscular junction where they mediate neuromuscular transmission, and neuronal receptors, which are found throughout the peripheral and central nervous system where they are involved in fast synaptic transmission. nAChRs are pentameric structures that are made up of combinations of individual subunits. Twelve neuronal nAChR subunits have been described, α2–α10 and β2–β4; these are differentially expressed throughout the nervous system and combine to form nAChRs with a wide range of physiological and pharmacological profiles. The nAChR has been proposed as a model of an allosteric protein in which effects arising from the binding of a ligand to a site on the protein can lead to changes in another part of the molecule. A great deal is known about the structure of the pentameric receptor. The extracellular domain contains binding sites for numerous ligands, which alter receptor behavior through allosteric mechanisms. Functional studies have revealed that nAChRs contribute to the control of resting membrane potential, modulation of synaptic transmission and mediation of fast excitatory transmission. To date, ten genes have been identified in the human genome coding for the nAChRs. nAChRs have been demonstrated to be involved in cognitive processes such as learning and memory and control of movement in normal subjects. Recent data from knockout animals has extended the understanding of nAChR function. Dysfunction of nAChR has been linked to a number of human diseases such as schizophrenia, Alzheimer's and Parkinson's diseases. nAChRs also play a significant role in nicotine addiction, which is a major public health concern. A genetically transmissible epilepsy, ADNFLE, has been associated with specific mutations in the gene coding for the α4 or β2 subunits, which leads to altered receptor properties. Electronic Publication     

On human speech,syntax, and language

The evolution of human speech and syntax, which appear to be the defining characteristics of modern human beings, is discussed. Speech depends on the morphology of the mouth, tongue, and larynx which yield the human «vocal tract», and neural mechanisms that facilitate the perception of speech and make possible the control of the articulatory gestures that underly speech. The neural mechanisms that underly human syntax may have derived by means of the Darwinian process of preadaption from the structures of the brain that first evolved to facilitate speech motor control. Recent data consistent with this theory are presented; deficits in the comprehension of syntax of normal aged people are correlated with a slowdown in speech rate.     

Cancer Reviews 2021 series: Cancer evolution: Darwin and beyond

Clinical and laboratory studies over recent decades have established branched evolution as a feature of cancer. However, while grounded in somatic selection, several lines of evidence suggest a Darwinian model alone is insufficient to fully explain cancer evolution. First, the role of macroevolutionary events in tumour initiation and progression contradicts Darwin''s central thesis of gradualism. Whole‐genome doubling, chromosomal chromoplexy and chromothripsis represent examples of single catastrophic events which can drive tumour evolution. Second, neutral evolution can play a role in some tumours, indicating that selection is not always driving evolution. Third, increasing appreciation of the role of the ageing soma has led to recent generalised theories of age‐dependent carcinogenesis. Here, we review these concepts and others, which collectively argue for a model of cancer evolution which extends beyond Darwin. We also highlight clinical opportunities which can be grasped through targeting cancer vulnerabilities arising from non‐Darwinian patterns of evolution.     

Beyond the DP/DSS controversy

Paul Turke's “Which humans behave adaptively, and why does it matter?” shows, if he we are to take him as being representative of “Darwinian social science” in general, that his school of thought has moved surprisingly close to that of its “Darwinian psychology” critics in accepting the importance if not the primacy of the psychological level of explanation in applying evolutionary theory to human behavior. Disagreements continue over whether the adaptiveness of current behavior should be viewed as an occasionally interesting question because of the light it can shed on evolved psychological mechanisms, or whether, as Turke maintains, it is the central question for human sociobiology. In any event, the “vertically integrated approach,” utterly ignored by Turke, incorporates Darwinian Psychology and is far more powerful than is Turke's approach in explicating the relationship between genes and culture, thereby rendering the current debate pointless.     

Really taking Darwin seriously: An alternative to Michael Ruse's Darwinian metaethics

Michael Ruse has proposed in his recent book Taking Darwin Seriously and elsewhere a new Darwinian ethics distinct from traditional evolutionary ethics, one that avoids the latter's inadequate accounts of the nature of morality and its failed attempts to provide a naturalistic justification of morality. Ruse argues for a sociobiologically based account of moral sentiments, and an evolutionary based casual explanation of their function, rejecting the possibility of ultimate ethical justification. We find that Ruse's proposal distorts, overextends and weakens both Darwinism and naturalism. So we propose an alternative Darwinian metaethics that both remedies the problems in Ruse's proposal and shows how a Darwinian naturalistic account of the moral good in terms of human fitness avoids the naturalistic fallacy and can provide genuine, even if limited, justifications for substantive ethical claims. Thus, we propose to really take Darwin seriously.The authors are equally responsible for the writing of this paper.     

Structural Capacitance in Protein Evolution and Human Diseases

Canonical mechanisms of protein evolution include the duplication and diversification of pre-existing folds through genetic alterations that include point mutations, insertions, deletions, and copy number amplifications, as well as post-translational modifications that modify processes such as folding efficiency and cellular localization. Following a survey of the human mutation database, we have identified an additional mechanism that we term “structural capacitance,” which results in the de novo generation of microstructure in previously disordered regions. We suggest that the potential for structural capacitance confers select proteins with the capacity to evolve over rapid timescales, facilitating saltatory evolution as opposed to gradualistic canonical Darwinian mechanisms. Our results implicate the elements of protein microstructure generated by this distinct mechanism in the pathogenesis of a wide variety of human diseases. The benefits of rapidly furnishing the potential for evolutionary change conferred by structural capacitance are consequently counterbalanced by this accompanying risk. The phenomenon of structural capacitance has implications ranging from the ancestral diversification of protein folds to the engineering of synthetic proteins with enhanced evolvability.