Classical Evolutionary Theory Research Articles

Medicina evolucionaria una ciencia básica emergente: an emergent basic science

Evolutionary Medicine is an emergent basic science that offers new and varied perspectives to the comprehension of human health. The application of classic evolutionary theories (descent with modification, and natural selection) to the human organism, to its pathogens, and their mutual co-evolution, provides new explanations about why we get sick, how we can prevent this, and how we can heal. Medicine has focused mainly on the proximate or immediate causes of diseases and the treatment of symptoms, and very little on its evolutionary or mediate causes. For instance, the present human genome and phenotypes are essentially paleolithic ones: they are not adapted to modern life style, thus favoring the so-called diseases of civilization (ie: ateroesclerosis, senescence, myopia, phobias, panic attacks, stress, reproductive cancers). With the evolutionary approach, post-modern medicine is detecting better the vulnerabilities, restrictions, biases, adaptations and maladaptations of human body, its actual diseases, and its preventions.

Prey for Long Life

An inspirational guest on the Sally Jesse Raphael show might tell viewers to make the most of the time they have. Organisms naturally follow that advice, at least according to classical evolutionary theory: To maximize their chances of passing their genes to offspring, they fall apart at different rates, depending on their prospects for survival. But a new study suggests that the simple rule doesn't always apply. Belying the theory, tropical guppies menaced by ravenous predators age more slowly than do guppies from more peaceful waters. The work suggests that scientists need to use more refined theories to describe how evolution shapes life span.

What evidence is there for the existence of individual genes with antagonistic pleiotropic effects?

Classical evolutionary theory predicts the existence of genes with antagonistic effects on longevity and various components of early-life fitness. Quantitative genetic studies have provided convincing evidence that such genes exist. However, antagonistic pleiotropic effects have rarely been attributed to individual loci. We examine several classes of longevity-assurance genes: those involved in regulation of the gonad; the insulin-like growth factor pathway; free-radical scavenging; heat shock proteins and apoptosis. We find initial evidence that antagonistic pleiotropic effects are pervasive in each of these classes of genes and in various model systems—although most studies lack explicit studies of fitness components. This is particularly true of human studies. Very little is known about the early-life fitness effects of longevity loci. Given the possible medical importance of such effects we urge their future study.

Stability of Mixed Nash Equilibria in Symmetric Quantum Games

In bimatrix games the Bishop–Cannings theorem of the classical evolutionary game theory does not permit pure evolutionarily stable strategies (ESSs) when a mixed ESS exists. We find the necessary form of two-qubit initial quantum states when a switch-over to a quantum version of the game also changes the evolutionary stability of a mixed symmetric Nash equilibrium.

Rethinking the evolutionary theory of aging: transfers, not births, shape senescence in social species.

The classic evolutionary theory of aging explains why mortality rises with age: as individuals grow older, less lifetime fertility remains, so continued survival contributes less to reproductive fitness. However, successful reproduction often involves intergenerational transfers as well as fertility. In the formal theory offered here, age-specific selective pressure on mortality depends on a weighted average of remaining fertility (the classic effect) and remaining intergenerational transfers to be made to others. For species at the optimal quantity-investment tradeoff for offspring, only the transfer effect shapes mortality, explaining postreproductive survival and why juvenile mortality declines with age. It also explains the evolution of lower fertility, longer life, and increased investments in offspring.

The ecology and genetics of fitness in Chlamydomonas. VIII. The dynamics of adaptation to novel environments after a single episode of sex.

According to classical evolutionary theory, sexual recombination can generate the variation necessary to adapt to changing environments and thereby confer an evolutionary advantage of sexual over asexual reproduction. Using the green alga, Chlamydomonas reinhardtii, we investigated the effect of a single sexual episode on adaptation of heterotrophic growth on different carbon sources. In an initial mixture of isolates, sex was induced and the resulting offspring constituted the sexual populations, along with any unmated vegetative cells; the unmated mixture of isolates represented the asexual populations. Mean and variance in division rates (i.e., fitness) were measured four times during approximately 50 generations of vegetative growth in the dark on all possible combinations of four carbon sources. Consistent with effects of recombination of epistatic genes in linkage disequilibrium, sexual populations initially had a higher variance in fitness, but their mean fitness was lower than that of asexual populations, possibly due to recombinational load. Subsequently, fitness of sexual populations exceeded that of asexual ones, but finally they regained parity in both mean and variance of fitness. Although recombination was not more effective on more complex substrates, these results generally support the idea that sex can accelerate adaptation to novel environments.

Positive genetic correlation between parasite resistance and body size in a free-living ungulate population.

Parasite resistance and body size are subject to directional natural selection in a population of feral Soay sheep (Ovis aries) on the island of St. Kilda, Scotland. Classical evolutionary theory predicts that directional selection should erode additive genetic variation and favor the maintenance of alleles that have negative pleiotropic effects on other traits associated with fitness. Contrary to these predictions, in this study we show that there is considerable additive genetic variation for both parasite resistance, measured as fecal egg count (FEC), and body size, measured as weight and hindleg length, and that there are positive genetic correlations between parasite resistance and body size in both sexes. Body size traits had higher heritabilities than parasite resistance. This was not due to low levels of additive genetic variation for parasite resistance, but was a consequence of high levels of residual variance in FEC. Measured as coefficients of variation, levels of additive genetic variation for FEC were actually higher than for weight or hindleg length. High levels of additive genetic variation for parasite resistance may be maintained by a number of mechanisms including high mutational input, balancing selection, antagonistic pleiotropy, and host-parasite coevolution. The positive genetic correlation between parasite resistance and body size, a trait also subject to sexual selection in males, suggests that parasite resistance and growth are not traded off in Soay sheep, but rather that genetically resistant individuals also experience superior growth.

Determinants of Intraspecific Brood Amalgamation in Waterfowl

-Intraspecific brood amalgamation in waterfowl can occur before hatching, when females lay eggs in the nests of conspecifics, or after hatching, when females abandon their young to the care of other conspecific families. Using phylogenetic information, I examined whether evolutionary transitions to intraspecific prehatching and posthatching brood amalgamation in waterfowl can be associated with certain life-history and ecological variables. Transitions to intraspecific prehatching brood amalgamation occurred more frequently in lineages carrying the colonial-breeding state and the cavity-nesting state. However, such transitions occurred equally frequently in lineages carrying different life histories as indexed by the ratio of clutch mass to female body mass. The results support the view that opportunities for successful amalgamation, which are thought to be higher in colonial-nesting and cavity-nesting species, act as a proximate determinant of prehatching brood amalgamation. Transitions to posthatching brood amalgamation occurred most often in lineages carrying the prehatching brood-amalgamation state, which suggests that amalgamation after hatching represents an extension of amalgamation before hatching that temporally increases the window of opportunity for brood mixing. Received 27 October 1995, accepted 16 July 1996. AS A RESULT of intraspecific brood amalgamation, parents provide care to unrelated young in many species of mammals (Packer et al. 1992), birds (Eadie et al. 1988), fishes (Johnston 1994, Fraser and Keenleyside 1995), and insects (Mappes et al. 1995, Petanidou et al. 1995, Premoli and Sella 1995). Initially a puzzling case for classic evolutionary theory, intraspecific brood amalgamation can increase reproductive success of adoptive parents, adopted young, and/or genetic parents (Riedman 1982, Eadie et al. 1988, Sayler 1992). Among birds, intraspecific brood amalgamation arises in two ways. Prehatching brood amalgamation (preHBA) occurs when one female lays eggs in the nest of a conspecific that incubates the clutch and subsequently raises the offspring. Posthatching brood amalgamation (postHBA) occurs when the young from one family mix permanently with offspring from another conspecific family. The two types of intraspecific brood amalgamation are common in species that have self-feeding young, such as waterfowl. Nevertheless, the determinants of 1 Present address: Faculty of Veterinary Medicine, University of Montr6al, CP 5000, St-Hyacinthe, Quebec J2S 7C6, Canada. E-mail: beauchgu@ere.umontreal.ca intraspecific brood amalgamation in waterfowl are poorly known (Eadie et al. 1988, Rohwer and Freeman 1989, Afton and Paulus 1992, Sayler 1992). Various life-history and ecological determinants of intraspecific preHBA and postHBA in waterfowl have been suggested on the basis of comparative studies that commonly use individual species or genera as independent units of analysis. The validity of these claims is questionable, however, because phylogenetic information rarely is used. For example, it is conceivable that information from tribes with many species inflated some life-history and ecological correlations (Harvey and Pagel 1991). Consequently, I examined whether evolutionary transitions to intraspecific preHBA and postHBA in waterfowl are associated with certain life-history and ecological variables using the phylogenetic classification proposed by Livezey (1991; 1995a, b, c; 1996). Below, I review the non-phylogenetically based determinants of intraspecific brood amalgamation that have been suggested in earlier waterfowl studies. Determinants of preHBA. -Discussions of the determinants of intraspecific preHBA have focused on nest visibility, nest density, parental behavior, and reproductive effort. Nest visibility and nest density may reflect the ease with

Spatial evolutionary game theory: Hawks and Doves revisited

We consider a spatial generalization of evolutionary game theory in which strategies are distributed over a spatial array of sites. We assume that the strategy corresponding to a given site has local interactions with the strategies sitting on neighbouring sites, and that the strategies change if neighbouring strategies are doing better. After briefly setting the stage with a formal definition of spatial evolutionary game theory, we consider the spatial extension of the Hawk-Dove game, and we show that the results are qualitatively different from those obtained from classical evolutionary game theory. For example, the proportion of Hawks in the population is in general lower in the spatial game than in the classical one. We also consider spatial generalizations of the extensions of the Hawk-Dove game obtained by including strategies such as Retaliator and Bully. Here, too, the results from the spatial game are very different from the classical results. In particular, with space Retaliator is a much more successful strategy than one would expect from classical considerations. This suggests that, in general, spatial structure may facilitate the evolution of strategies such as Retaliator, which do not necessarily prosper classically, and which are reminiscent of the \`nice', \`provokable' and `forgiving' strategies which seem to play a central role in the evolution of cooperation. The results indicate that including spatial structure in evolutionary game theory is a fruitful extension.

NUCLEAR RIBOSOMAL DNA VARIATION AMONG RAMETS AND GENETS OF WHITE CLOVER.

Central to population and evolutionary biology is understanding the sources and consequences of genetic variation revealed at various levels of organization: within and among individuals, populations, and taxa. Classical evolutionary theory emphasizes the role that variability plays in influencing the evolutionary potential of a population or taxon. Consequently, there are hundreds of studies for plants alone published on population level sources of genetic variation (Hamrick and Godt, 1990). In contrast there is a dearth of studies in population biology that have examined the occurrences or consequences of within individual genetic (i.e., somatic) variation (King and Schaal, 1990; Rogers et al., 1986; Schaal and Learn, 1988; Silander, 1985). Even fewer have attempted to place such studies in the context of genetic variation at various levels of organization (Schaal, 1985). The evolutionary significance of somatic variation continues to be a source of considerable speculation in plant population biology (Antolin and Strobeck, 1985; Klekowski, 1988; Silander, 1985; Walbot and Cullis, 1985; Whitham et al., 1984). The little documented information available is often ambiguous or difficult to interpret evolutionarily, and is met with skepticism (see review by Klekowski, 1988). If somatic variation is likely to have some evolutionary significance, vegetatively propagating plant populations are a likely place to begin a search (see Klekowski, 1988). Advantageous somatic variants can be perpetuated indefinitely in clonal plants even if they are not immediately incorporated into the germ line. Indeed some of the best direct evidence for the occurrence of somatic variation and its potential evolutionary significance comes from studies of natural, clonal populations of plants (Klekowski, 1988; Schaal, 1985; Schaal and Learn, 1988; Silander, 1985). This study focusses on genetic variation in nuclear ribosomal DNA (rDNA) from accessions of natural clover populations. Genetic variation in rDNA was found to be common among genets (i.e., genetic individuals) of white clover (Trifolium repens), as well as among different species of clover. This was due to both restriction site and restriction fragment length

Sociological theory: Looking forward

A brief model of the rise, salience, criticism, and relative decline of theoretical perspec tives in sociology is sketched, citing the dominance of sociological positivism in the early part of the twentieth century as an example. Classical evolutionary theory and structural-functionalism are also mentioned as illustrations. Viewing the contemporary theoretical scene, the author sees a kind of peaceful pluralism as a visible motif, and some modest signs of integrative or synthetic theoretical activity on the horizon.

CARBON AND NITROGEN ABUNDANCES IN OLD, VERY METAL-POOR STARS : A REPRISE BASED ON THE LOW-RESOLUTION LICK SURVEY.

ABSTRACT A summary is given of the carbon and nitrogen abundances found in the Lick survey of nearly 300 old, very metal-poor stars (Fe/H of less than -1.3). The survey consists of population samples drawn from various stellar subsystems of the Galaxy as well as different stages of stellar evolution. The question of whether a systematic pattern of carbon depletion and nitrogen enhancement emerges within the data was examined and three conclusions were made: (1) the average value of (C + N)/Fe lies within narrow limits for all stellar subsystems, suggesting that the large nitrogen enhancement found in many evolved metal-poor stars is the result of interior C and N mixing; (2) the degree of carbon depletion and corresponding nitrogen enhancement is much larger than predicted by classical evolutionary theory; and (3) the extensive CN processing that occurs in evolved metal-poor stars proceeds further in some stellar subsystems than in others. This is particularly true of the most metal-poor halo field giants vis-a-vis giants in M15 and M92.

Carbon and nitrogen abundances in giant stars of the metal-poor globular cluster M15

view Abstract Citations (122) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Carbon and nitrogen abundances in giant stars of the metal-poor globular cluster M15. Trefzger, D. V. ; Langer, G. E. ; Carbon, D. F. ; Suntzeff, N. B. ; Kraft, R. P. Abstract The authors derive carbon and nitrogen abundances for 33 giant-star members of the globular cluster M15, thus extending their earlier work in M92 to another cluster of comparably low metallicity ([M/H] ⪉ -2). They describe a technique for obtaining C and N abundances which is based on spectrophotometric indices that measure the strengths of NH, CN, and CH bands in low-resolution scanner spectra. The spectrophotometric indices are calibrated using scanner spectra of M92 giant stars in which estimates of C and N abundances had previously been obtained by the method of spectrum synthesis. The complex behavior of C and N abundances in M15 giants cannot be adequately described by models based on classical evolutionary theory. The scenarios already advanced to explain these abundance patterns in the case of M92 are discussed briefly in connection with M15. Publication: The Astrophysical Journal Pub Date: March 1983 DOI: 10.1086/160765 Bibcode: 1983ApJ...266..144T Keywords: Abundance; Giant Stars; Globular Clusters; Stellar Evolution; Stellar Spectrophotometry; Carbon Stars; Interstellar Extinction; Late Stars; Metallicity; Nitrogen; Stellar Spectra; Astrophysics full text sources ADS | data products SIMBAD (28)

Are individuals really subordinated to genes? A theory of living entities

Abstract Modern evolutionary theory consists of an explicit theory of change and an implicit theory of the existence of living entities. A theory of the latter type, called the theory of the process of living (POL), is proposed. It contains a two-level definition of living entities, an analysis of possible and impossible similarity and differences between parents and offspring, and a logical division of the information governing the functioning of a living organism. The theory of POL emphasizes the proceeding of living entities in time while the modern evolutionary theory emphasizes the types of entities proceeding in time. The theory of POL produces a basis for reanalysing relations between individuals, their genes and the environment. It produces some predictions deviating from classic evolutionary theory. These conflicts occur in areas where analyses of genetic dynamics have made implicit assumptions of rules of POL. For example, the theory of POL states that the genetic relatedness of successive generations is a technical solution more than the reason of reproduction, that genetic relatedness as such does not imply altruism between individuals and that genes are the tools whereby organisms exist and not the contrary. Implications of the theory of POL on paradoxes of evolutionary theory are discussed.

Carbon and nitrogen abundances in giant stars of the metal-poor globular cluster M92

view Abstract Citations (225) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Carbon and nitrogen abundances in giant stars of the metal-poor globular cluster M 92. Carbon, D. F. ; Langer, G. E. ; Butler, D. ; Kraft, R. P. ; Suntzeff, N. B. ; Kemper, E. ; Trefzger, C. F. ; Romanishin, W. Abstract The 169 low resolution image tube scanner spectra obtained at the Lick Observatory for 71 stars in the field of M92, covering the 3100-5200 A spectral interval, are matched with synthetically generated spectra to find the C and N abundances for a subset of 45 bright member giants. It is found that (1) stars side by side in the color-magnitude diagram show N and C abundance variations by factors of 10 and three, respectively, (2) the segregation of stars into small groups by effective temperature and log g shows no inversely proportional relationship between N and C abundance, and (3) the mean C abundance is 10 times smaller on the AGB than on the SGB. The C and N abundances of M92 therefore disagree with the predictions of classical evolutionary theory. Four different scenarios which have been suggested to account for the observations cited are discussed. In addition, primordial CNO abundances observed in, or deduced for, metal-poor field and cluster stars are compared with those deduced for M92, and then discussed in connection with the global galactic nucleosynthesis and cluster self-contamination process scenarios. Publication: The Astrophysical Journal Supplement Series Pub Date: June 1982 DOI: 10.1086/190796 Bibcode: 1982ApJS...49..207C Keywords: Abundance; Giant Stars; Globular Clusters; Late Stars; Stellar Evolution; Stellar Spectra; Asymptotic Giant Branch Stars; Atomic Spectra; Carbon; Color-Magnitude Diagram; Hyperfine Structure; Image Dissector Tubes; Molecular Spectra; Nitrogen; Nuclear Fusion; Solar Spectra; Stellar Atmospheres; Stellar Models; Stellar Temperature; Ubv Spectra; Astrophysics full text sources ADS | data products SIMBAD (76)