By-product Of Selection Research Articles

Developing the Gaia Theory. A Response to the Criticisms of Kirchner and Volk

This paper is a response to the recent criticisms of Gaia theory by Kirchner and Volk, in this journal (Kirchner, 2002; Volk, 2002). As noted by Kirchner, there is a need for more dialogue on this topic, and we write in this spirit with the intention of helping clear a pathway ‘Toward a future for Gaia theory’, to use Volk’s phrase. We agree with Kirchner and Volk on a number of points. Our purpose here is to clarify outstanding differences and suggest how they may be resolved, in the hope that this will help form a basis for developing the Gaia theory. ‘Gaia’ is a particular type of open thermodynamic system, planetary in scale with abundant life tightly coupled to its environment. Planet Earth hosts the only known example, for which the name ‘Gaia’ was introduced. The Gaia theory aims to explain the development and functioning of Gaia systems, and is currently restricted to this one example. Our central point is that the functioning of such systems must be consistent with natural selection occurring within them, but this does not mean that planetary-scale regulation has to be the product of natural selection. We try to move from the more general questions raised by Volk to the more specific issues tackled by Kirchner. We begin by considering what constitutes a reasonable basis for generalising about the behaviour of Gaia systems (Section 2). Then we consider the possible explanations for the persistence of life on Earth (Section 3). We associate the ‘Gaia theory’ with the idea that regulatory feedbacks are a probable outcome on planets with abundant life, but note that if this is proved wrong and the existence of regulatory feedbacks on Earth turns out to be good luck, this still leaves an important research agenda. We briefly review the basic tenets of the Gaia theory (Section 4), and expand on the facts that Gaia systems are expected to contain both positive and negative feedback (Section 5), and both feedback from by-products of selection (Section 6) and feedback involving natural selection (Section 7). Means of distinguishing the results of environmental enhancement and adaptation to the environment are suggested (Section 8). We conclude by discussing how conceptions of Gaia have contributed to the emerging field of ‘Earth system science’ (Section 9).

The cellular lethality of radiation-induced chromosome translocations in human lymphocytes.

Recent evidence has shown that translocation frequencies decline over time. This phenomenon might be explained by the co-occurrence of translocations in cells that also contain dicentrics, in which case translocations would be eliminated as a by-product of selection against dicentrics. Alternatively, a fraction of translocations may themselves be lethal. Here we describe our initial approaches to develop mathematical models to test whether the decline in translocation frequencies results from the first, the second, or a combination of these two possibilities. The models assumed that all chromosome exchanges were simple, i.e., were comprised of dicentrics as well as one-way and two-way translocations. Complex aberrations (three or more breaks in two or more chromosomes) were not modeled, nor were fragments or intrachromosomal exchanges (rings, inversions). We tested the models using Monte Carlo simulations, and then we fitted the models to data describing chromosome aberration frequencies induced by a single acute in vitro exposure to (137)Cs gamma rays in human peripheral blood lymphocytes from two donors. Chromosome painting was used to enumerate translocations and dicentrics from 2 to 7 days after exposure. Our results indicate that in donor no. 2, the decline in translocation frequencies occurs as a by-product of selection against dicentrics. However, in donor no. 1, whose cells appeared more radiosensitive than cells from donor no. 2, up to 40% of the one-way translocations may themselves be lethal at high doses, although calculations indicate that two-way translocations do not cause lymphocyte mortality. Individual variation in the probability that translocations are lethal to cells appears to be important, and one-way translocations appear to be lethal more often than two-way translocations. Within the limits of these models, these findings indicate that both postulated mechanisms, i.e. inherent lethality and selection against dicentrics in the same cells, contribute to the loss of both one-way and two-way translocations.

Paradigms and pitfalls of yeast longevity research

Over the past 10 years, considerable progress has been made in the yeast aging field. Multiple lines of evidence indicate that a cause of yeast aging stems from the inherent instability of repeated ribosomal DNA (rDNA). Over 16 yeast longevity genes have now been identified and the majority of these have been found to affect rDNA silencing or stability. Environmental conditions such as calorie restriction have been shown to modulate this mode of aging via Sir2, an NAD-dependent histone deacetylase (HDAC) that binds at the rDNA locus. Although this mechanism of aging appears to be yeast-specific, the longevity function of Sir2 is conserved in at least one multicellular organism, Caenorhabditis elegans ( C. elegans). These findings are consistent with the idea that aging is a by-product of natural selection but longevity regulation is a highly adaptive trait. Characterizing this and other mechanisms of yeast aging should help identify additional components of longevity pathways in higher organisms.

Reduction of Phallus in Birds: An Avian Way to Safe Sex?

In contrast to other organisms with internal fertilization, males of the majority of birds do not possess a copulatory organ. Causes of this loss of phallus are not well understood. Copulations in birds are very short, indicating selection for fast transfer of sperm. I propose here that the loss of phallus is mainly a by-product of selection for rapid copulations, and present two hypotheses to explain this loss: (1) Predation Avoidance. During copulation birds temporarily lose ability to fly, which strongly reduces their ability to escape predator attacks. Insemination with the phallus cannot be accomplished in a few seconds. Therefore, the reduction of phallus would result in acceleration of sperm transfer and shortening of the period of exposure to an elevated predation risk. (2) Copulation Efficiency. In most birds, the copulating male stands on the female's back in a very unstable position. A faster sperm transfer because of the loss of a phallus would result in fewer interrupted copulations due to loss of balance as well as in reduced risk of the female being injured if the male loses balance.

Insurance ovulation, embryo mortality and twinning.

The 'insurance ova' hypothesis (Anderson, 1990) views dizygotic twinning as a by-product of selection for multiple ovulation which sometimes--in error--results in the birth of twins. From this viewpoint, polyovulation is a mechanism which reduces the risks of fertilization failure or embryo defect/mortality. If DZ twin births are a 'side-effect' of a mechanism which compensates for defective embryos one might predict that embryo defect rates and twinning rates will covary. This prediction is tested using national-level data on twinning rates and rates of trisomy-21 (Down's syndrome), and a strong positive correlation is found, even when controlling for maternal age. One suggestion that follows from this finding is that intra- and interpopulation variation in both twinning rates and Down's syndrome rates may result, in part, from individual variation in pre-implantation rejection of embryos in the very early stages of pregnancy. In this paper it is proposed that the 'insurance ova' explanation for twinning in humans could be expanded to incorporate a model of rejection of anomalous embryos, be they anomalies of number or type. Variation in the efficiency of an embryo rejection mechanism, combined with variation in frequency of polyovulation, would have consequences for individual reproductive success.

Biography vs Biology in Visual Aesthetic Preference

Theories concerning the human aesthetic sense are rarely based on moderate views. While Immanuel Kant argued that the aesthetic judgment is strictly independent of the knowledge of things ( Critique of Judgment, §15, page 1795), modern biological research suggests that the aesthetic sense emerged as a by-product of natural selection for the recognition of signals. We tested such theories by measuring the effect of cognitive training on aesthetic preference. Using a psychometric method of paired comparisons we obtained preference data by presenting to twenty-two naive observers 16 compound Gabor signals that were equally spaced on a full ‘circle of form’ in a 2-D feature space. Subjects were then trained to classify the same patterns into four deliberately defined pattern classes. The effect of this learning procedure was then assessed in another preference experiment. We show that our preference data can be explained in terms of two factors: pattern complexity and pattern symmetry. Cognitive learning (ie biography) significantly affected the complexity factor, while the symmetry factor remained invariant. We argue that these findings are inconsistent with the extreme positions of both Kant and the biologists. Rather, they imply that aesthetic preference is being determined by the interplay of ‘pre-wired’ biological functions of signal recognition and of individual experience.

Sex differences and evolutionary by-products

AbstractFrom the perspective of evolutionary theory, we believe it makes more sense to view the sex differences in spatial cognition as being an evolutionary by-product of selection for optimal rates of fetal development. Geary does not convince us that his proposed selective factors operated with “sufficient precision, economy, and efficiency.” Moreover, the archaeological evidence does not support his proposed evolutionary scenario.

The multiple sides of the same tool: Cognitive development as a matter of social constructions and meanings

The study of cognitive development in children has moved through several identifiable phases in the last twenty years. Butterworth (1992) suggests a first shift from a focus on intellectual processes within the individual child, as in the classic Piagetian studies towards an understanding of the interpersonal context of cognitive growth, but contextual factors were for the most part seen only as moderators of this growth. A second shift seems to us theoretically more important: when theorists began to explore the inextricable links between contextual constraints and the acquisition of knowledge, thus underlying 'the social' not as a mere collection of moderating variables but as a constituent of 'what cognition really is'. The fruitfulness of interplay between 'the social' and 'the cognitive' has been recommended a long time ago by Levy-Bruhl who, according to Luria (1976), was among the first scholars to point out the qualitative feature of primitive thought and to treat logical processes as products of historical development. He had a great influence on the psychologists of the 1920's who tried to go beyond simplistic notions about the mind as a by-product of natural selection and to understand human consciousness as a product of sociocultural development. As Moscovici (1990) suggests, there are at least two ways of approaching the interplay

Adaptive Phenotypic Plasticity: Target or By-Product of Selection in a Variable Environment?

Adaptive Phenotypic Plasticity: Target or By-Product of Selection in a Variable Environment?

Theism as a By-Product of Natural Selection

Previous articleNext article No AccessTheism as a By-Product of Natural SelectionJack D. Maser and Gordon G. Gallup, Jr.Jack D. Maser Search for more articles by this author and Gordon G. Gallup, Jr. Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Journal of Religion Volume 70, Number 4Oct., 1990 Article DOIhttps://doi.org/10.1086/488474 Views: 6Total views on this site Citations: 5Citations are reported from Crossref Copyright 1990 The University of ChicagoPDF download Crossref reports the following articles citing this article:Ajit Varki Did Human Reality Denial Breach the Evolutionary Psychological Barrier of Mortality Salience? A Theory that Can Explain Unusual Features of the Origin and Fate of Our Species, (Oct 2019): 109–135.https://doi.org/10.1007/978-3-030-25466-7_6Jesse M. Bering The Existential Theory of Mind, Review of General Psychology 6, no.11 (Mar 2002): 3–24.https://doi.org/10.1037/1089-2680.6.1.3Thomas J Bouchard, Matt McGue, David Lykken, Auke Tellegen Intrinsic and extrinsic religiousness: genetic and environmental influences and personality correlates, Twin Research 2, no.0202 (Feb 2012): 88–98.https://doi.org/10.1375/twin.2.2.88Dean Falk Braindance oder das Hirn der schönen Künste, (Jan 1994): 187–210.https://doi.org/10.1007/978-3-0348-6181-6_9Terrence W. Tilley Reformed Epistemology in a Jamesian Perspective, Horizons 19, no.11 (Sep 2014): 84–98.https://doi.org/10.1017/S0360966900025676

Natural hybrids of Papilio (Insecta: Lepidoptera): poor taxonomy or interesting evolutionary problem?

A minimum of 6% of Papilio species hybridize in nature, with most hybrids derived from parents within the same species group. Extensive laboratory hybridization between Papilio species indicates relatively little postzygotic incompatibility and suggests that most barriers to gene flow are prezygotic. In some species, mating behavior appears to be a by-product of selection on ecologically important traits. For example, larval host shifts in P. machaon in western North America may have led to changes in its mating sites and phenology. The extent of these changes can be related to the frequency of hybridization between P. zelicaon and P. machaon. In another species, P. glaucus, gene flow between two distinct subspecies may be decreased by genetic linkage between ecologically important traits on sex chromosomes. Although current information for Papilio species indicates that most species differences developed in allopatry, the observed connection between ecological traits and mating traits suggests the possibility of significant divergence in parapatry or sympatry. The persistent formation of natural hybrids between otherwise distinct species of Papilio supports the view that species are populations primarily maintained by ecological selection.

Age Specificity and Ecological Theory

This paper attempts first to deal with the question of aging as a byproduct of natural selection, drawing on the theories of Medawar, Williams and Hamilton, and second, to apply the conclusions to considerations of population and behavioral ecology. It is concluded that: (1) Age—specific mortality should drop to a minimum prior to earliest reproductive age and then rise with age. (2) Age—specific fecundity should rise with age to a peak, which may occur at almost any age depending on the sort of organism considered, and then fall. (3) A sudden increase in mortality at a given age will result in natural selection favoring higher relative mortality at immediately preceding and following ages, and lowered fecundity immediately after that age. (4) A sudden increase in fecundity at a given age will result in natural selection favoring relative higher mortality in early life and immediately after that age, as well as relaxed selection for increased fecundity, especially at middle and late ages. (5) Selection acts to make increasingly steep the survivorship curve of a population declining or fluctuating due to changes in mortality. (6) Selection acts to postpone reproductive effort in populations declining or fluctuating due to changes in fecundity. (7) If mortality is very low, animals, as they age, should ideally take greater risks to secure reproductive success. (8) The nature of altruistic behavior may be age specific, with older individual more characteristically altruistic and younger individuals more characteristically pampered. (9) Intergroup hostilities should be largely directed toward certain age groups.

DEGENERATION AND RELICT ADAPTATION

RECENT advances in biology have shed considerable light on the evolutionary fate of originally adaptive structures which have since become functionless. It is a commonplace that in the great majority of animals such organs degenerate and either disappear entirely or become vestigial, while often showing excessive variability. This tendency to degeneration (and excess variation) of functionless organs appears to be automatic in sexually reproducing organisms with any considerable degree of outbreeding, like the great majority of higher animals. In such cases, as Muller1 has pointed out, mutation-pressure alone will tend to cause useless organs to degenerate. Sewall Wright2, while agreeing with this view, believes that a more important factor operating in the same direction is the prevalence of multiple-factor (polygene) systems of genes with multiple (pleiotropic) effects, in the genetic make-up of organisms. Wherever this is so, “the evolutionary changes in a system of genes, some bringing increased development and others reduced development in those parts of the organism which are under direct selection, should have a net effect on indifferent parts in the direction of reduced development”. Further, when linked polygenic systems exist (that is, polygene systems consisting of one or more sets of genes which show genetic linkage with each other) and two such systems are lodged in the same chromosome or chromosomes, then anything which promotes change in the one will, by virtue of the resultant general recombination, promote change in the other. Thus, if selection is acting to alter the main character controlled by one such system, while the character controlled by the second is selectively neutral or useless, the resultant recombination will 'break up' the useless character, and in virtue of the obvious tendency of change to be towards decreased efficiency unless kept up to the mark by selection, this will promote degeneration of the useless feature. Degeneration of useless organs is thus genetically inevitable, partly as the direct effect of mutation pressure, partly indirectly as a by-product of selection acting on polygene systems with multiple effects.