Maynard-Smith Research Articles

Evolution and strategic stability: From maynard smith to kohlberg and mertens

A simple and intuitive condition on a set of strategy profiles guarantees that the set has a strategically stable subset. The condition arises naturally in evolutionary contexts.

Aggressive Motivation in the Midas Cichlid: Evidence for Behavioral Efference

Behavioral Efference is a hypothetical positive feedback from the performance of an aggressive display that augments the level of aggressive motivation. The hypothesis was proposed (BOND, 1989) to account for the occurrence of truthful communication during aggressive encounters, even in the face of a presumed selective pressure in favor of deceit (MAYNARD SMITH, 1984). Evidence of Behavioral Efference was sought in an experimental study of adult Midas cichlids Cichlasoma citrinellum, in which subjects responded aggressively to varying sizes of dummy fish. Before and after each aggression trial, the level of aggressive motivation was estimated from the intensity of the subject's attacks on conspecific juveniles. A weighted index of aggressiveness that objectively combined the frequencies of four aggressive action patterns was obtained using detrended correspondence analysis. Aggression indices from aggression trials, as well as from intertrial intervals, furnished a basis for comparison of two causal models: behavioral efference, which assumes that post-stimulus motivation is substantially influenced by display performance, and Direct Stimulus Mediation, which assumes that the displays themselves play no immediate causal role. When the subjects actively displayed to the stimulus dummy, the results showed no significant correlation between the size of the dummy and the magnitude of the motivational effect. However, a significant relationship was demonstrated between the level of aggressive display and subsequent increases in aggressive motivation, in precise accord with the Behavioral Efference model. Direct Stimulus Mediation was evident only in trials in which the subject displayed no overt aggression toward the stimulus object. An account of the functional significance of Behavioral Efference is provided, suggesting that the feedback serves to regulate the intensity of aggressive interactions by preparing the displaying individual for active combat.

List of contributions

(1) The evolutionary biology of molecular parasites by s. NEE and j. MAYNARD SMITH.

The evolutionary advantage of recombination. II. Individual selection for recombination.

Based on the FISHER-MULLER theory of the evolution of recombination, an argument can be constructed predicting that a recessive allele favoring recombination will be favored, if there are either favorable or deleterious mutants occurring at other loci. In this case there is no clear distinction between individual and group selection. Computer simulation of populations segregating for recessive or dominant recombination alleles showed selection favoring recombination, except in the case of a dominant recombination allele with deleterious background mutants. The relationship of this work to parallel investigations by WILLIAMS and by STROBECK, MAYNARD SMITH, and CHARLESWORTH is explored. All seem to rely on the same phenomenon. There seems no reason to assume that the evolution of recombination must have occurred by group selection.

CORRIGENDUM

IOCHEMICAL studies of certain proteins have recently shown that the rate of evolution or gene substitution is much higher than that previously thought (KIMURA 1968; DAYHOFF 1969). This high rate of gene substitution has aroused a great deal of controversy about HALDANE’S (1957; 1960) theory of the cost of natural selection. HALDANE postulated that the genetic deaths needed to secure gene substitution by natural selection lower the average fitness of a population, so that there is an upper limit to the number of gene substitutions per unit length of time, depending on the fertility of the species in question. In this case the fitness of a genotype was assumed to be constant. HALDANE’S theory was accepted by KIMURA (1960; 1967) and CROW (1968) but questioned by a number of authors. Among others, SVED (1968) and MAYNARD SMITH (1968) have argued that if the population size is regulated in a density-dependent manner and gene substitution occurs by competitive selection, the mean fitness of the population would not necessarily be reduced. They produced a model of threshold selection in which gene substitutions may occur at a much higher rate than HALDANE’S computation allows. Recently, MATHER (1969) developed an interesting model of competitive selection and showed that many classical formulae for the change in gene frequency hold true under competitive selection. He, however, argued that the cost of natural selection should be re-examined, taking into account competitive selection and the effect of selection on population size. He thought that the cost of selection would be much less than HALDANE’S computation suggests. Another type of model for competitive selection was developed by SCHUTZ and UZANIS (1969). In this model, however, neither the cause and process of competition nor the mechanism of population regulation was studied in detail. The purpose of the present paper is first to develop mathematical models for natural selection in regulated populations and then examine the adequacy of the theory of the cost of natural selection. The cost of natural selection will be looked at from a slightly different angle, and the fertility excess or genetic variance of fitness necessary for a given rate of gene substitution will be studied. It will be shown that competition itself does not lead to threshold selection and HALDANE’S conclusion is essentially correct.

Group Selection and Kin Selection

DR. MAYNARD SMITH'S communication raises a good many more questions than I can attempt to answer here. The major obstacle to constructive discussion between us really arises from the understandable (though regrettable) differences in outlook and experience between a laboratory geneticist and a field ecologist. To me his picture of territorial systems and other aspects of conventional behaviour appears scarcely true or comprehensive enough to provide a basis for valid deduction; my own grasp of the genetical theory of natural selection, on the other hand, no doubt looks still more halting and inept to him. We ought to enlarge the area of common ground, but that is too big a task to discharge effectively here.

Body size and weight in relation to varicocoele and hernia.

Annals of Human GeneticsVolume 21, Issue 4 p. 304-312 BODY SIZE AND WEIGHT IN RELATION TO VARICOCOELE AND HERNIA SHEILA MAYNARD SMITH, SHEILA MAYNARD SMITHSearch for more papers by this author SHEILA MAYNARD SMITH, SHEILA MAYNARD SMITHSearch for more papers by this author First published: May 1957 https://doi.org/10.1111/j.1469-1809.1972.tb00201.xCitations: 12AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume21, Issue4May 1957Pages 304-312 RelatedInformation

REVIEWS

REVIEWS Get access Atonement, by H. MAYNARD SMITH, (London: Macmillan and Co., 1925.) What is the Atonement? A Study in the Passion of God in Christ, by H. MALDWYN HUGHES (London: James Clarke and Co.) J. K. MOZLEY J. K. MOZLEY Search for other works by this author on: Oxford Academic Google Scholar The Journal of Theological Studies, Volume os-XXVIII, Issue January, January 1927, Pages 192–194, https://doi.org/10.1093/jts/os-XXVIII.January.192 Published: 01 January 1927

FRANK WESTON, BISHOP OF ZANZIBAR: AN APPRECIATION

International Review of MissionVolume 14, Issue 2 p. 188-197 FRANK WESTON, BISHOP OF ZANZIBAR: AN APPRECIATION H. MAYNARD SMITH D.D., H. MAYNARD SMITH D.D.Search for more papers by this author H. MAYNARD SMITH D.D., H. MAYNARD SMITH D.D.Search for more papers by this author First published: April 1925 https://doi.org/10.1111/j.1758-6631.1925.tb04632.xCitations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume14, Issue2April 1925Pages 188-197 RelatedInformation

REVIEWS

Journal Article REVIEWS Get access The Church of England, by the ARTHUR C. HEADLAM Bishop of Gloucester, with an appendix by the H. MAYNARD SMITH, Canon of Gloucester. ( John Murray, 1924.) J. M. CREED J. M. CREED Search for other works by this author on: Oxford Academic Google Scholar The Journal of Theological Studies, Volume os-XXVI, Issue 102, January 1925, Pages 218-b–221, https://doi.org/10.1093/jts/os-XXVI.102.218-b Published: 01 January 1925