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Discusses the book "Narrow Roads of Gene Land: The Collected Papers of W.D. Hamilton," vol.2, "The Evolution of Sex," by W. D. Hamilton. Details of Hamilton's explanation of sex, through his theory of Parasite Red Queen Theory; Details of Hamilton's concept of eugenics and the human genome; Views of Hamilton on the dangers of genetic disorientation.

Science progresses faster when researchers operate within an explicit framework of concepts and theories, but currently biology has no explicit, overarching conceptual framework and few general theories. The single general theory currently recognized is that of evolution, which was put forth by Charles Darwin 150 years ago. Recently, Scheiner and Willig (2008) explicated a similarly general theory of ecology. In this paper, using the theory of evolution as an exemplar, I discuss the nature of theory in biology and put forth an overarching theory, as well as new general theories for cells, organisms, and genetics. Along with the theories of evolution and ecology, these constitute a general conceptual framework for the biological sciences. This framework reveals linkages among the various parts of biology, makes explicit the assumptions behind more narrow theories and models, and provides new insights into the structures of biological theories. This framework can also be used as a teaching tool, moving the teaching of biology beyond the transference of a vast compendium of facts. My hope is that this essay will lead to a vigorous discussion and debate across all of biology about the nature and structure of its theories. [ABSTRACT FROM AUTHOR]

Evolutionary genetics has recently made enormous progress in understanding how geneticvariation maps into phenotypic variation. However, why some Waits are phenotypically invariant despite apparent genetic and environmental changes has remained a major puzzle. In the 1940s, Conrad Hal Waddington coined the concept and term "canalization" to describe the robustness of phenotypes to perturbation; a similar concept was proposed by Waddington's contemporary Ivan Ivanovich Schmalhausen. This paper reviews what has been learned about canalization since Waddington. Canalization implies that a genotype's phenotype remains relatively invariant when individuals of a particular genotype are exposed to different environments (environmental canalization) or when individuals of the same single- or multilocus genotype differ in their genetic background (genetic canalization). Consequently, genetic canalization can be viewed as a particular kind of epistasis, and environmental canalization and phenotypic plasticity are two aspects of the same phenomenon. Canalization results in the accumulation of phenotypically cryptic genetic variation, which can be released after a "decanalizing" event. Thus, canalized genotypes maintain a cryptic potential for expressing particular phenotypes, which are only uncovered under particular decanalizing environmental or genetic conditions. Selection may then act on this newly released genetic variation. The accumulation of cryptic genetic variation by canalization may therefore increase evolvability at the population level by leading to phenotypic diversification under decanalizing conditions. On the other hand, under canalizing conditions, a major part of the segregating genetic variation may remain phenotypically cryptic canalization may therefore, at least temporarily, constrain phenotypic evolution. Mechanistically, canalization can be understood in terms of transmission patterns, such as epistasis, pleiotropy, and genotype by environment interactions, and in terms of genetic redundancy, modularity, and emergent properties of gene networks and biochemical pathways. While different forms of selection can favor canalization, the requirements for its evolution are typically rather restrictive. Although there are several methods to detect canalization, there are still serious problems with unambiguously demonstrating canalization, particularly its adaptive value. [ABSTRACT FROM AUTHOR]

Organisms adapt developmental and physiological features to local and transient conditions in part by modulating transcription, translation, and protein functions, usually without changing DNA sequences. Remarkably, these epigenetic changes sometimes endure through meiosis and gametogenesis, thereby affecting phenotypic variation across generations, long after epigenetic changes were triggered. Transgenerational effects challenge our traditional understanding of inheritance. In this review, we focus on patterns of inheritance, molecular features, mechanisms that lead from environmental and genetic perturbations to phenotypic variation in later generations, and issues about study design and replication. [ABSTRACT FROM AUTHOR]

Contemporary Darwinian medicine is a still-expanding new discipline, one of whose principal aims is to arrive at an evolutionary understanding of those aspects of the body that leave it vulnerable to disease. Historically, there was a precedent for this research; between 1880 and 1940, several scientists tried to develop some general evolutionary theories of disease as arising from deleterious traits that escape elimination by natural selection. In contrast, contemporary Darwinian medicine uses evolutionary theory to consider all the possible reasons why selection has left humans vulnerable to disease. [ABSTRACT FROM AUTHOR]

This review describes new developments in the study of transgenerational epigenetic inheritance, a component of epigenetics. We start by examining the basic concepts of the field and the mechanisms that underlie epigenetic inheritance. We present a comprehensive review of transgenerational cellular epigenetic inheritance among different taxa in the form of a table, and discuss the data contained therein. The analysis of these data shows that epigenetic inheritance is ubiquitous and suggests lines of research that go beyond present approaches to the subject. We conclude by exploring some of the consequences of epigenetic inheritance for the study of evolution, while also pointing to the importance of recognizing and understanding epigenetetic inheritance for practical and theoretical issues in biology. [ABSTRACT FROM AUTHOR]

We discuss the evolutionary origin and elaboration of sociality using an indirect genetic effects perspective. Indirect genetic effects models simultaneously consider zygotic genes, genes expressed in social partners (especially mothers and siblings), and the interactions between them. Incorporation of these diverse genetic effects should lead to more realistic models of social evolution. We first review haplodiploidy as a factor that promotes the evolution of eusociality. Social insect biologists have doubted the importance of relatedness asymmetry caused by haplodiploidy and focused on other predisposing factors such as maternal care. However indirect effects theory shows that maternal care evolves more readily in haplodiploids, especially with inbreeding and despite multiple mating. Because extended maternal care is believed to be a precondition for the evolution of eusociality, the evolutionary bias towards maternal care in haplodiploids may result in a further bias towards eusociality in these groups. Next, we compare kin selection and parental manipulation and then briefly review additional hypotheses for the evolutionary origin of eusociality. We present a verbal model for the evolutionary origin and elaboration of sib-social care from maternal care based on the modification of the timing of expression of maternal care behaviors. Specifically, heterochrony genes cause maternal care behaviors to be expressed prereproductively towards siblings instead of postreproductively towards offspring. Our review demonstrates that both maternal effect genes (expressed in a parental manipulation manner) and direct effect zygotic genes (expressed in an offspring control manner) are likely involved in the evolution of eusociality. We conclude by describing theoretical and empirical advances with indirect genetic effects and sociogenomics, and we provide specific quantitative genetic and genomic predictions from our heterochrony model for the evolutionary origin and elaboration of eusociality. [ABSTRACT FROM AUTHOR]