Global voices of science. Teaching evolution in Mexico: preaching to the choir.
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Biological Evolution↗
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Results for “Evolution of cooperation”
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Tunicate Thy-1--an invertebrate member of the Ig superfamily.
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Animals↗
Interactions between learning and evolution: the outstanding strategy generated by the Baldwin effect.
The Baldwin effect is known as an possible interaction between learning and evolution, where individual lifetime learning can influence the course of evolution without using any Lamarckian mechanism. Our concern is to consider the Baldwin effect in dynamic environments, especially when there is no explicit optimal solution through generations and this solution depends only on interactions among agents. We adopted the iterated Prisoner's Dilemma as a dynamic environment, introduced phenotypic plasticity into its strategies, and conducted computational experiments, in which phenotypic plasticity is allowed to evolve. The Baldwin effect was observed in the experiments as follows: First, strategies with enough plasticity spread, which caused a shift from defect-oriented populations to cooperative populations. Second, these strategies were replaced by a strategy with a modest amount of plasticity generated by interactions between learning and evolution. By making three kinds of analysis, we have shown that this strategy provides outstanding performance in comparison with other deterministic strategies. Further experiments towards open-ended evolution have also been conducted so as to generalize our results.
Adaptation, Physiological↗
Antibody evolution constrains conformational heterogeneity by tailoring protein dynamics.
The evolution of proteins with novel function is thought to start from precursor proteins that are conformationally heterogeneous. The corresponding genes may be duplicated and then mutated to select and optimize a specific conformation. However, testing this idea has been difficult because of the challenge of quantifying protein flexibility and conformational heterogeneity as a function of evolution. Here, we report the characterization of protein heterogeneity and dynamics as a function of evolution for the antifluorescein antibody 4-4-20. Using nonlinear laser spectroscopy, surface plasmon resonance, and molecular dynamics simulations, we demonstrate that evolution localized the Ab-combining site from a heterogeneous ensemble of conformations to a single conformation by introducing mutations that act cooperatively and over significant distances to rigidify the protein. This study demonstrates how protein dynamics may be tailored by evolution and has important implications for our understanding of how novel protein functions are evolved.
Animals↗
Kin competition within groups: the offspring depreciation hypothesis.
Where relatives compete for the same resources (kin competition) and each obtains an equal share, this can favour the evolution of elevated dispersal rates, such that most resource competition is among non-relatives. We show that this effect evaporates as among-sibling dominance increases to the point where the allocation of resources is maximally unequal. We restore a kin-competition effect on emigration rates from dominance-ranked family groups by showing that where siblings form queues to inherit the breeding positions, the length of the queue affects the fitness of all individuals by depreciating the rank of subsequent offspring. Incorporating this 'offspring depreciation' effect decreases optimal queue lengths, increases dispersal rates and explains the otherwise paradoxical use of sinks by cooperatively breeding birds in stable environments. The offspring depreciation effect also favours the evolution of small, but consistent, clutch sizes and high reproductive skew, but constrains the evolution of alloparenting.
Animals↗
Recognition of idiotypes in lymphocyte interactions. II. Antigen-independent cooperation between T and B lymphocytes that possess similar and complementary idiotypes.
Antigen-independent cooperation between T and B lymphocytes is demonstrated in vitro in two different experimental protocols: (a) B cells from A/J mice immunized in vivo either with Group A streptococcal vaccine (Strep A) or with the IgG1 fraction of guinea pig anti-idiotypic antibody to the A5A idiotype, mature into plaque-forming cells (PFC) with specificity for Group A streptococcal carbohydrate (A-CHO) during a 4-day culture together with T cells from A/J mice immunized in vivo with A5A idiotypic antibody. (b) B cells from A/J mice immunized in vivo with Strep.A generate PFC specific for A-CHO when cultured in the presence of small concentrations of anti-A5A idiotypic antibody and of T cells primed with Strep.A. In both cases, antigen-independent cooperation is idiotypically selective, such that only those B cells respond that secrete antibody with the A5A idiotype. The data are interpreted to suggest that, in addition to antigen-specific helper cells, idiotype-specific may participate in antibody responses, and that the latter type of help may be responsible for the idiotypic selectivity in T-B cooperation observed previously. Furthermore, idiotype-specific cooperation may be a means to generate and maintain B cell diversity during the evolution and ontogeny of the immune system.
Animals↗
REM and NREM sleep as natural accompaniments of the evolution of warm-bloodedness.
Divergence of primitive sleep into REM and NREM states is thought to have occurred in the nocturnal Triassic ancestors of mammals as a natural accompaniment of the evolution of warm-bloodedness. As ambient temperatures during twilight portions of primitive sleep traversed these evolving ancestors' core temperature, mechanisms of thermoregulatory control that employ muscle contractions became superfluous. The resulting loss of need for such contractions during twilight sleep led to muscle atonia. With muscle tone absent, selection favored the persistence of the fast waves of nocturnal activity during twilight sleep. Stimulations by these waves reinforce motor circuits at the increasing temperatures of evolving warm-bloodedness without leading to sleep-disturbing muscle contractions. By these and related interlinked adaptations, twilight sleep evolved into REM sleep. The daytime period of sleep became NREM sleep. The evolution of NREM and REM sleep following this scenario has implications for sleep's maintenance processes for long-term memories. During NREM sleep, there is an unsynchronized, uncoordinated stimulation and reinforcement of individual distributed component circuits of consolidated memories by slow wave potentials, a process termed 'uncoordinated reinforcement'. The corresponding process during REM sleep is the coordinated stimulation and reinforcement of these circuits by fast wave potentials. This action temporally binds the individual component circuit outputs into fully formed memories, a process termed 'coordinated reinforcement'. Sequential uncoordinated and coordinated reinforcement, that is, NREM followed by REM sleep, emerges as the most effective mechanism of long-term memory maintenance in vertebrates. With the evolution of this two-stage mechanism of long-term memory maintenance, it became adaptive to partition sleep into several NREM-REM cycles, thereby achieving a more lengthy application of the cooperative sequential actions.
Adaptation, Physiological↗
Sex, the Prisoner's Dilemma Game, and the evolutionary inevitability of cooperation.
It will be a universal feature of sexual populations that individuals prefer mates with typical rather than rare characteristics--essentially because most mutations reduce fitness. This is termed koinophilia. Koinophilia will also apply to behaviour. In particular, individuals will prefer mates that behave in social interactions that follow whatever rules are common in that population. Suppose that individuals interact in situations which can be represented by the Iterated Prisoner's Dilemma Game (IPD). If koinophilia is ignored, previous authors have shown that it is hard to find an evolutionarily stable strategy, and that strategies cycle indefinitely. However, if koinophilia is included, it has the effect of increasing the fitness of whatever happens to be the common strategy. This, in turn, has the effect of stabilizing almost any strategy (that has, for whatever reason, become the local norm) in the IPD. Different, partially isolated groups will thus become evolutionarily trapped in different behaviours, which are defended against alternative strategies originating through mutation or immigration. Groups that happen, by chance, to reach a cooperative strategy will be fitter, as groups, than those that reach defection (even though, in one-to-one encounters, it is the selfish individual who always wins). The ultimate result will be the replacement of selfish groups by cooperative groups.
Animals↗
A major histocompatibility complex class I allele shared by two species of chimpanzee.
Little is known regarding the rates at which natural selection can modify or retain antigen presenting alleles at the major histocompatibility complex (MHC). Discovery of identical [1101 base pairs (bp)] coding regions at the MHC class I C locus in Pan troglodytes and Pan paniscus, chimpanzee species that diverged approximately 2.3 million years ago, now indicates that a class I allotype can survive for at least this period. Remarkable conservation was also reflected in the (1799 bp) introns where a maximum of only six substitutions distinguished five alleles (three from P. troglodytes and two from P. paniscus) that encoded the identical heavy chain allotype. Analysis of a more distantly related human allele, HLA-Cw*0702, corroborated that intron variation was non-uniform along the gene. Thus we provide a clear reference frame for the lifetime of an MHC class I allotype, a direct estimate of allelic substitution rates, and evidence for an unusual evolution of MHC class I introns.
Alleles↗
Evolutionary game dynamics with non-uniform interaction rates.
The classical setting of evolutionary game theory, the replicator equation, assumes uniform interaction rates. The rate at which individuals meet and interact is independent of their strategies. Here we extend this framework by allowing the interaction rates to depend on the strategies. This extension leads to non-linear fitness functions. We show that a strict Nash equilibrium remains uninvadable for non-uniform interaction rates, but the conditions for evolutionary stability need to be modified. We analyze all games between two strategies. If the two strategies coexist or exclude each other, then the evolutionary dynamics do not change qualitatively, only the location of the equilibrium point changes. If, however, one strategy dominates the other in the classical setting, then the introduction of non-uniform interaction rates can lead to a pair of interior equilibria. For the Prisoner's Dilemma, non-uniform interaction rates allow the coexistence between cooperators and defectors. For the snowdrift game, non-uniform interaction rates change the equilibrium frequency of cooperators.
Biological Evolution↗
Development of trauma care systems.
The modern-day history of trauma care system development encompasses a 45-year period. This report provides a timeline that highlights significant organizational and legislative initiatives that established the foundation of the current trauma system in the United States. The rationale for moving toward a public health approach in addressing trauma system development is explored and supported. Finally, the present-day issues confronting continued trauma system evolution and future opportunities are presented.
History, 20th Century↗
A selective history of groin hernia surgery in the early 19th century. The anatomic atlases of Astley Cooper, Franz Hesselbach, Antonio Scarpa, and Jules-Germain Cloquet.
One of the most important eras in the evolution of groin hernia surgery is that of the early 19th century. It was a time when cadaver dissections and diverse clinical studies culminated in a more thorough anatomic understanding of the inguinal canal. For reasons cloaked in permanent historical uncertainty, the style of hernia textbook publishing also dramatically changed at the turn of the 19th century when sumptuous anatomical atlases, exemplified by those of Astley Cooper, Franz Hesselbach, Antonio Scarpa, and Jules-Germain Cloquet, began to appear. Characterized by the presence of numerous detailed engravings these texts were expensive to publish and often had limited print runs. The publishing history and clinical impact of these now rare hernia tomes are analyzed in this article.
Anatomy, Artistic↗
Four years analysis of cancer genetic clinics activity in France from 1994 to 1997: a survey on 801 patients. French Cooperative Network/Groupe Génétique et Cancer de la Fédération Nationale des Centres de Lutte Contre le Cancer.
AIM: In order to evaluate the characteristics and the evolution of cancer genetics activity in France, a survey was conducted at the national level during a period of 4 years from 1994 to 1997 through the French Cooperative Network, a multidisciplinary group formed to investigate inherited tumors. METHOD: A questionnaire was sent to all the 29 French non-specialized cancer genetic clinics to evaluate activity during a period of 4 consecutive weeks each year from 1994 to 1997. Items concerning the cancer genetic clinics, the consultees and the types of consultation were explored. RESULTS: A total number of 801 consultees were seen during the period of analysis. Some prominent characteristics of patients attending cancer genetic clinics were found. The majority of these are women (88%), and the mean age of consultees is 48 years. Fifty five percent of consultees are affected with cancer, and breast (personal and/or family history) is the most frequent site involved (63%). A genetic predisposition is certain or likely in about 53% of cases and unlikely in only 13% of consultations. The majority of consultations are devoted to new families (71%). The mean duration of consultations is 50 minutes, but 40% have a duration of at least 1 hour. Variations of several parameters during the 4 years period were observed and analyzed. Finally, since duration of consultations (more or equal to 1 hour) and personal or family history of breast/ovarian cancer appeared as pivotal elements in our study and consequently may affect the organization of clinics and the structuring as well as the evolution of cancer genetic activity in France, we analyzed more precisely the factors significantly associated with these 2 elements. CONCLUSION: Study compliance was fair (60% of centers) and these results give a good measure of cancer genetic activity in France. The variation of parameters from one year to another may reflect modifications in medical practice (medical orientation rather than research focus and content of cancer genetic clinics) and/or scientific breakthroughs in cancer genetics such as identification of genes predisposing to cancer.
Adult↗
From reciprocity to unconditional altruism through signalling benefits.
Cooperation among genetically unrelated individuals is commonly explained by the potential for future reciprocity or by the risk of being punished by group members. However, unconditional altruism is more difficult to explain. We demonstrate that unconditional altruism can evolve as a costly signal of individual quality (i.e. a handicap) as a consequence of reciprocal altruism. This is because the emergent correlation between altruism and individual quality in reciprocity games can facilitate the use of altruism as a quality indicator in a much wider context, outside the reciprocity game, thus affecting its further evolution through signalling benefits. Our model, based on multitype evolutionary game theory shows that, when the additive signalling benefit of donating help exceeds the cost for only some individuals (of high-quality state) but not for others (of low-quality state), the population possesses an evolutionarily stable strategy (ESS) profile wherein high-quality individuals cooperate unconditionally while low-quality individuals defect or play tit-for-tat (TfT). Hence, as predicted by Zahavi's handicap model, signalling benefits of altruistic acts can establish a stable generosity by high-quality individuals that no longer depends on the probability of future reciprocation or punishment.
Altruism↗
Evolution of bacterial diversity and the origins of modularity.
A characteristic feature of all organisms is modular organisation: the tendency for groups of genes to interact in such a way as to limit the extent of pleiotropic effects among characters belonging to different functional complexes. While the implications of modularity for the evolution of variability have been much discussed the evolutionary origins remain obscure. Here we develop a model, with special reference to signal transduction cascades of bacteria, which predicts that in the face of ecological opportunity and lateral gene transfer, selection will favour modular genome architectures because such architectures minimise the pleiotropic effects associated with accommodation of potentially beneficial foreign DNA.
Base Composition↗
Evolution in group-structured populations can resolve the tragedy of the commons.
Public goods are the key features of all human societies and are also important in many animal societies. Collaborative hunting and collective defence are but two examples of public goods that have played a crucial role in the development of human societies and still play an important role in many animal societies. Public goods allow societies composed largely of cooperators to outperform societies composed mainly of non-cooperators. However, public goods also provide an incentive for individuals to be selfish by benefiting from the public good without contributing to it. This is the essential paradox of cooperation-known variously as the Tragedy of the Commons, Multi-person Prisoner's Dilemma or Social Dilemma. Here, we show that a new model for evolution in group-structured populations provides a simple and effective mechanism for the emergence and maintenance of cooperation in such a social dilemma. This model does not depend on kin selection, direct or indirect reciprocity, punishment, optional participation or trait-group selection. Since this mechanism depends only on population dynamics and requires no cognitive abilities on the part of the agents concerned, it potentially applies to organisms at all levels of complexity.
Animals↗
Evolutionary biology. Cooperation can be dangerous.
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Animals↗
Overlapping syndromes, undifferentiated connective tissue disease, and other fibrosing conditions.
Connective tissue diseases (CTDs) frequently present as undifferentiated disorders that may or may not develop into one of the well defined CTDs. The natural evolution of the early undifferentiated CTDs is not well known. Some years ago a cooperative study was started on 410 patients with early CTD; within this group, 48 patients had early scleroderma. Raynaud's phenomenon has been recognized as an early sign of CTD. Several studies on Raynaud's phenomenon patients have shown that abnormal nailfold capillary patterns have prognostic significance for evolution to a CTD, particularly scleroderma. Mixed connective tissue disease (MCTD) is the prototype of an overlap syndrome. The relevance of defining MCTD as a separate disease entity has been challenged. Follow-up studies show that many patients originally diagnosed with MCTD develop a definite CTD, particularly scleroderma or systemic lupus erythematosus, within a few years. In patients with MCTD, primary pulmonary hypertension is an important cause of death. This condition seems to be associated with anticardiolipin antibodies. A number of case reports suggest that immunosuppressive treatment is of benefit in this almost always fatal condition. The main reason for describing MCTD as a separate entity is its association with antibodies to U1-RNP. Recent studies have suggested that the production of anti-U1-RNP is an antigen-driven process, but the nature of the trigger for its production has not been elucidated. Retroviral proteins do not appear to be involved. Antibodies to the protein part of the U1-RNP complex and antibodies to the RNA component have been described. Levels of anti-RNA antibodies seem to parallel disease activity in MCTD patients.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗