The search for reality.
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Biological Evolution↗
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Results for “Evolution of cooperation”
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Comparative immunology.
Comparative Immunology has gained wide acceptance in biology, as an offspring of immunology and an amalgam of immunology and zoology. The prescient experiments of Metchnikoff on phagocytosis in invertebrates during the 19th century served to splinter immunology into its two main components: cellular and humoral. There is much interest in the immune system of invertebrates as representing early models or precursors of the innate system of vertebrates that by contrast possess the innate system as well as the more highly evolved adaptive system. With respect to mechanisms, we think of the invertebrate system as innate, natural, non-specific, non-anticipatory, and non-clonal. Innate immunity operates through leukocytes that are not components of the macrophage T and B interrelationships that characterize vertebrate adaptive immunity that is adaptive, induced, specific, anticipatory, and clonal. This symposium on invertebrate immunology has provided an overview of what is current and crucial to understanding the larger field of comparative immunology. Comparative immunology is now an established field, here since Metchnikoff but officially since about 1977, with a journal (Developmental and Comparative Immunology) (DCI) and an International Society of Developmental and Comparative Immunology (ISDCI). During this short but vigorous history several national, adherent societies have been organized in Japan, Italy and Germany with sporadic interest in a national group in the USA. Nevertheless, comparative immunology is here as vital to zoology in general and to immunology in particular as we delve deeper into unique but also shared characteristics.
Animals↗
Trends in recommendations of myelosuppressive chemotherapy for the treatment of breast cancer: evolution of the national comprehensive cancer network guidelines and the cooperative group studies.
Breast cancer, the most commonly occurring cancer in women in the United States, is the second most common cause of cancer-related mortality. Mortality rates in breast cancer have, however, declined by 2.3% per year from 1990 to 2001, partly because of the development of better chemotherapy agents and regimens, which have resulted in major changes in the standards of care. To study the changes in the past decade in expert opinion about the preferred chemotherapy for breast cancer, we compared the treatment guidelines of the National Comprehensive Cancer Network (NCCN) for 1996, 2000, and 2005. The myelotoxicity associated with the NCCN-recommended agents was also assessed by using data from the prescribing information for the drugs. This review showed that many of the agents, combinations of agents, and new dosing schedules currently recommended in the NCCN guidelines for the treatment of breast cancer are associated with myelosuppression. Many of these myelosuppressive regimens, which were used in the past to treat advanced-stage or metastatic disease, are now prescribed for early-stage disease. Furthermore, the cytotoxic agents and regimens recommended by the NCCN are more myelosuppressive than those recommended a decade ago. Many oncologists are aware of this trend toward the more intensive treatment of patients with cancer and take proactive steps to minimize the risk of myelosuppression and its complications.
Adult↗
Genetics of epithelial tumors of the renal parenchyma in adults and renal cell carcinoma in children.
The classification of renal cell carcinomas has been affected by both the delineation of new histologic subtypes and the understanding that recognized histomorphologic patterns are reflective of specific sets of cytogenetic abnormalities. In fact, standard methods of clinicopathologic study and cytogenetic analysis have been cooperatively contributory in the evolution of current concepts regarding the biologic nature and classification of renal parenchymal epithelial tumors. In this review, the current classification scheme for these tumors is discussed from the perspective of both the defining histologic and cytogenetic features. Limited molecular data are described as well.
Adenocarcinoma, Clear Cell↗
Biotechnology and the creation of ethics.
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Biological Evolution↗
[The influence of man and society on biomedical progress].
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Aging↗
Evolution of indirect reciprocity in groups of various sizes and comparison with direct reciprocity.
Recently many studies have investigated the evolution of indirect reciprocity through which cooperative action is returned by a third individual, e.g. individual A helped B and then receives help from C. Most studies on indirect reciprocity have presumed that only two individuals take part in a single interaction (group), e.g. A helps B and C helps A. In this paper, we investigate the evolution of indirect reciprocity when more than two individuals take part in a single group, and compare the result with direct reciprocity through which cooperative action is directly returned by the recipient. Our analyses show the following. In the population with discriminating cooperators and unconditional defectors, whether implementation error is included or not, (i) both strategies are evolutionarily stable and the evolution of indirect reciprocity becomes more difficult as group size increases, and (ii) the condition for the evolution of indirect reciprocity under standing reputation criterion where the third individuals distinguish between justified and unjustified defections is more relaxed than that under image scoring reputation criterion in which the third individuals do not distinguish with. Furthermore, in the population that also includes unconditional cooperators, (iii) in the presence of errors in implementation, the discriminating strategy is evolutionarily stable not only under standing but also under image scoring if group size is larger than two. Finally, (iv) in the absence of errors in implementation, the condition for the evolution of direct reciprocity is equivalent to that for the evolution of indirect reciprocity under standing, and, in the presence of errors, the condition for the evolution of direct reciprocity is very close to that for the evolution of indirect reciprocity under image scoring.
Altruism↗
Emergence of cooperation among interacting individuals.
We study the evolution of interacting individuals located on the sites of a regular lattice. The individuals play a two action game in which the players either cooperate or defect with respect to a certain issue. The main rule of the game is that a player does not change his action when he and his opponent have held the same action in the previous round. Numerical simulations performed on a square lattice show a stationary state in which the lattice has a finite number of cooperators and defectors and two frozen states, one full of cooperators and the other full of defectors.
Journal Article↗
Cumulative benefit games: achieving cooperation when players discount the future.
Experimental studies with captive animals show strong preferences for immediate reward. Several authors have argued that these tendencies to discount delayed reward may severely limit the Iterated Prisoner's Dilemma game as a model of animal cooperation. This paper explores a simple mechanism, dubbed cumulative games, that can, in principle, promote cooperative action even when there is strong temporal discounting. In the simplest type of cumulative game a pair of players does not receive benefits at the end of each play, as in a conventional repeated game, but must complete a sequence of games before collecting the accumulated benefits. In a preliminary analysis pitting tit-for-tat against all-D, I show that accumulation can promote a conditionally cooperative strategy even when there is strong temporal discounting. However, the delays created by accumulation de-value the pairwise interaction, so although the relative value of cooperation increases, the total value of the interaction decreases. I investigate accumulation further by simulating the evolution of a broader class of strategies. These simulation studies show that accumulation, and small discounting rates (high future value) can both promote cooperative action. The limitations of these results are discussed.
Animals↗
Interleukin-2 and phytohaemagglutinin stimulate the proliferation of tunicate cells.
Proliferative responses of cells in tunicate pharyngeal explants to human interleukins and mitogenic lectins were tested. Increased tritiated-thymidine [( 3H]-TdR) uptake was detected among pharyngeal cells incubated with recombinant human interleukin-2 (IL-2), and phytohaemagglutinin-P (PHA-P). Responses to IL-2 were dose-dependent and affected lymphocyte-like cells. Enhanced proliferation was stimulated by IL-2 in the absence of co-stimulants and was not synergized by co-incubation with human interleukin-1 (IL-1) or PHA-P. Anti-IL-2 polyclonal antibody inhibited the stimulatory activity of recombinant human interleukin-2 (rhIL-2). Of three lectins tested (concanavalin-A [Con-A], pokeweed mitogen [PWM] and PHA-P), only PHA-P proved to be mitogenic. Con-A and PWM did not significantly increase proliferative activity even though both lectins were capable of binding pharyngeal cells as revealed by flow cytometry and fluorescence microscopy. Similarly, human IL-1 had no effect on [3H]-TdR uptake either alone or in combination with IL-2 and PHA-P. These data suggest that the functions of some interleukin-like cytokines have been conserved during evolution.
Animals↗
The coevolution of altruism and punishment: role of the selfish punisher.
Punishment is an important mechanism promoting the evolution of altruism among non-relatives. We investigate the coevolution of altruism and punitive behavior, considering four possible strategies: the altruist punisher (AP, a cooperator who punishes defectors), the altruist non-punisher (AN, a pure cooperator), the selfish punisher (SP, a defector who punishes defectors), and the selfish non-punisher (SN, a pure defector). The SP uses a paradoxical strategy as it punishes other defectors. We analyse the effects of SP and AN on the coevolution of altruism and punishment. We study both the score-dependent viability model (whereby the game's score affects survivorship only) and the score-dependent fertility model (whereby the score affects fertility only). In the viability model of a completely mixed population, SP first drives out SN, and hence it helps cooperators (AP and AN) to evolve. In contrast, in the fertility model of a completely mixed population, neither SP nor AN helps the evolution of cooperation. In both the viability and fertility models of a lattice-structured population, SP promotes the spread of AP. In contrast, AN discourages the evolution of AP. These results can be understood that punishment is a form of spite behavior, paying a cost to reduce the fitness of the opponents, and that different models give different magnitude of advantage to spite behavior.
Altruism↗
Life support system development in West Germany.
The delivery of fully qualified Environmental Control and Life Support System (ECLS) flight hardware for the Spacelab Flight Unit was completed in 1979, and the first Spacelab flight is scheduled for mid 1983. With Spacelab approaching its operational stage, ESA has initiated the Follow-on Development Programme. The future evolution of Spacelab elements in a continued U.S./European cooperation is obviously linked to the U.S. STS evolution and leads from the sortie-mode improvements (Initial Step) towards pallet systems and module applications in unmanned and manned space platforms (Medium and Far Term Alternatives). Extensive studies and design work have been accomplished on life support systems for Life Sciences Laboratories (Biorack) in Spacelab (incubators and holding units for low vertebrates). Future long term missions require the implementation of closed loop life support systems and in order to meet the long range development cycle feasibility studies have been performed. Terrestrial applications of the life support technologies developed for space have been successfully implemented.
Animals↗
Long-run cooperation in the one-shot Prisoner's Dilemma: a hierarchic evolutionary approach.
This paper proposes a hierarchic evolutionary model leading to long-run cooperation in the Prisoner's Dilemma. The population is segmented into groups, and evolution and interaction take place 'in parallel' at two levels: (i) within groups at the lower level; (ii) among groups at the higher one. At each of these levels, what performs currently best tends to be imitated. On the other hand, occasionally, individuals also experiment with (or mutate to) some new strategy. If the number of groups is sufficiently large, the long-run (invariant) distribution of the process is shown to be concentrated on the cooperative outcome.
Animals↗
The evolution of reproductive restraint through social communication.
The evolution of altruistic behavior through group selection is generally viewed as possible in theory but unlikely in reality, because individual selection favoring selfish strategies should act more rapidly than group selection favoring cooperation. Here we demonstrate the evolution of altruism, in the form of conditional reproductive restraint based on an explicitly social mechanism, modulated by intrapopulation communication comprising signal and evolved response, in a spatially distributed predatory/parasitic/pathogenic model system. The predatory species consistently comes to exploit a signal implying overcrowding, individuals constraining their reproduction in response, with a corresponding increase in equilibrium reproduction rate in the absence of signal. This signaled restraint arises in a robust way for a range of model spatial systems; it outcompetes non-signal-based restraint and is not vulnerable to subversion by noncooperating variants. In these systems, communication is used to evaluate population density and regulate reproduction accordingly, consistent with central ideas of Wynne-Edwards [Wynne-Edwards, V. C. (1962) Animal Dispersion in Relation to Social Behavior (Hafner, New York)], whose claims about the evolutionary importance of group selection helped ignite decades of controversy. This quantitative simulation model shows how the key evolutionary transition from solitary living to sociality can occur. The process described here of cooperation evolving through communication may also help to explain other major evolutionary transitions such as intercellular communication leading to multicellular organisms.
Altruism↗
Evolution of altruism in optional and compulsory games.
In "optional" variants of the iterated prisoner's dilemma, players may choose whether or not to participate. Members of evolving populations playing optional variants of the iterated prisoner's dilemma by following inherited strategies tend to cooperate more than do members of populations playing the standard, "compulsory" version. This result is due to dynamical properties of the evolving systems: the populations playing the compulsory game can become stuck in states of low cooperation that last many generations, while the optional games provide routes out of such states to states of high cooperation. Computational simulations of the evolution of populations playing these games support these analytic results and illustrate the interactions between the genetic representation of strategies and the composition of populations in which those strategies are deployed.
Altruism↗
Evolution of spite through indirect reciprocity.
How can cooperation persist in the face of a temptation to 'cheat'? Several recent papers have suggested that the answer may lie in indirect reciprocity. Altruistic individuals may benefit by eliciting altruism from observers, rather than (as in direct reciprocity) from the recipient of the aid they provide. Here, we point out that indirect reciprocity need not always favour cooperation; by contrast, it may support spiteful behaviour, which is costly for the both actor and recipient. Existing theory suggests spite is unlikely to persist, but we demonstrate that it may do so when spiteful individuals are less likely to incur aggression from observers (a negative form of indirect reciprocity).
Aggression↗
Cooperation is fleeting in the world of transposable elements.
Composite transposons are key vehicles for the worldwide spreading of genes that allow bacteria to survive toxic compounds. Composite transposons consist of two smaller transposable elements called insertion sequences (ISs), which flank the genes that permit such survival. Each IS in a composite transposon can either transpose alone, selfishly, or it can transpose cooperatively, jointly with the other IS. Cooperative transposition can enhance an IS's chance of survival, but it also carries the risk of transposon destruction. I use game theory to show that the conditions under which cooperative transposition is an evolutionarily stable strategy (ESS) are not biologically realistic. I then analyze the distribution of thousands of ISs in more than 200 bacterial genomes to test the following prediction of the game-theoretical model: if cooperative transposition was an ESS, then the closely spaced ISs that characterize composite transposons should be more abundant in genomes than expected by chance. The data show that this is not the case. Cooperativity can only be maintained in a transitional, far-from-equilibrium state shortly after a selection pressure first arises. This is the case in the spreading of antibiotic resistance, where we are witnessing a fleeting moment in evolution, a moment in which cooperation among selfish DNA molecules has provided a means of survival. Because such cooperation does not pay in the long run, the vehicles of such survival will eventually disappear again. My analysis demonstrates that game theory can help explain behavioral strategies even for mobile DNA.
Animals↗
How should we define goodness?--reputation dynamics in indirect reciprocity.
Theory of indirect reciprocity is important in explaining cooperation between humans. Since a partner of a social interaction often changes, an individual should assess his partner by using social information such as reputation and make decisions whether to help him or not. To those who have 'good' social reputation does a player give aid as reciprocation, whereas he has to refuse to help those who have 'bad' reputation. Otherwise benefits of altruism is easily exploited by them. Little has been known, however, about the definition of 'goodness' in reputation. What kind of actions are and should be regarded as good and what kind of actions bad? And what sort of goodness enables sustaining exchange of altruism? We herein challenge this question with an evolutionary perspective. We generalize social reputation as 'Honor-score' (H-score) and examine the conditions under which individuals in a group stably maintain cooperative relationships based on indirect reciprocity. We examine the condition for evolutionarily stable strategies (ESSs) over 4096 possible cases exhaustively. Mathematical analysis reveals that only eight cases called 'leading eight' are crucial to the evolution of indirect reciprocity. Each in the leading eight shares two common characteristics: (i) cooperation with good persons is regarded as good while defection against them is regarded as bad, and (ii) defection against bad persons should be regarded as a good behavior because it works as sanction. Our results give one solution to the definition of goodness from an evolutionary viewpoint. In addition, we believe that the formalism of reputation dynamics gives general insights into the way social information is generated, handled, and transmitted in animal societies.
Altruism↗