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    Epigenetics as an answer to Darwin’s “special difficulty,” Part 2: natural selection of metastable epialleles in honeybee castes
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    Abstract:
    In a recent perspective in this journal, Brian R. Herb discussed how epigenetics is a possible mechanism to circumvent Charles Darwin’s “special difficulty” in using natural selection to explain the existence of the sterile-fertile dimorphism in eusocial insects. Darwin’s classic book “On the Origin of Species by Means of Natural Selection” explains how natural selection of the fittest individuals in a population can allow a species to adapt to a novel or changing environment. However, in bees and other eusocial insects, such as ants and termites, there exist two or more castes of genetically similar females, from fertile queens to multiple sub-castes of sterile workers, with vastly different phenotypes, lifespans, and behaviors. This necessitates the selection of groups (or kin) rather than individuals in the evolution of honeybee hives, but group and kin selection theories of evolution are controversial and mechanistically uncertain. Also, group selection would seem to be prohibitively inefficient because the effective population size of a colony is reduced from thousands to a single breeding queen. In this follow-up perspective, we elaborate on possible mechanisms for how a combination of both epigenetics, specifically, the selection of metastable epialleles, and genetics, the selection of mutations generated by the selected metastable epialleles, allows for a combined means for selection amongst the fertile members of a species to increase colony fitness. This “intra-caste evolution” hypothesis is a variation of the epigenetic directed genetic error (EDGE) hypothesis, which proposes that selected metastable epialleles increase genetic variability by directing mutations specifically to the epialleles. Natural selection of random metastable epialleles followed by a second round of natural selection of random mutations generated by the metastable epialleles would allow a way around the small effective population size of eusocial insects.
    Keywords:
    Eusociality
    Abstract ‘Levels of selection’ examines the levels-of-selection question, which asks whether natural selection acts on individuals, genes, or groups. This question is one of the most fundamental in evolutionary biology, and the subject of much controversy. Traditionally, biologists have mostly been concerned with selection and adaptation at the individual level. But, in theory, there are other possibilities, including selection on sub-individual units such as genes and cells, and on supra-individual units such as groups and colonies. Group selection, altruistic behaviour, kin selection, the gene-centric view of evolution, and the major transitions in evolution are all discussed.
    Group Selection
    Kin selection
    Positive selection
    Gene selection
    The way Elliott Sober conceives group selection implies two claims: a) that natural selection is a cause; b) that natural selection can act at multiple levels of biological organization and that these multi-level selection processes are distinct or independent from one another. However, a comparison of multi-level selection processes with the distinction between selection and random drift allows us to assert that, if we conceive group selection as Sober does, the possibility of accurately quantifying the contributions to evolutionary change of two selective processes acting at different levels is an essential step needed in order to properly distinguish between them. However, Sober’s endorsement of the Price approach to measuring group and individual selection contributions makes it impossible for him to support, at the same time, both of the claims indicated above. He is thus forced either to admit an essential interconnectedness between selective processes acting at different levels, or to deny that evolutionary change is causally determined by natural selection.
    Group Selection
    Citations (2)
    Darwin did not specify: “Species”. Darwin did not know the difference between “Phenotypic and Genotypic features”. “Natural Selection” cannot produce new species. Spontaneous mutations do not exist. Mutants have no offspring. Darwin did not make tests to confirm his theory. Evolution, with natural selection, is neither about the Origin of Life, nor about New Life but is about the Optimal Preservation of all existing living creatures.
    Creatures
    Charles darwin
    After clarifying how Darwin understood natural selection and common ancestry, I consider how the two concepts are related in his theory. I argue that common ancestry has evidential priority. Arguments about natural selection often make use of the assumption of common ancestry, whereas arguments for common ancestry do not require the assumption that natural selection has been at work. In fact, Darwin held that the key evidence for common ancestry comes from characters whose evolution is not caused by natural selection. This raises the question of why Darwin puts natural selection first and foremost in the Origin.
    Origin of species
    Common descent
    Citations (47)
    Knowledge of the pattern of selection in natural populations is fundamental for our understanding of the evolutionary process. Selection at higher levels has gained considerable theoretical support in recent years, and one possible level of selection is the breeding pair where fitness is a function of the pair and cannot be reduced to single individuals. We analyzed the importance of pair-level selection over 25 years in a natural population of the collared flycatcher. Pair-level selection was significant in five and probably in another 9 years. The relative importance of pair-level selection varied over years and can have stronger or the same strength as directional selection. This means that selection can act on the combination of the breeding pair in addition to selection on each individual separately. Overall, the conservative estimates obtained here show that this is a potentially important form of selection.
    Directional selection
    Stabilizing selection
    Citations (9)
    Abstract The argument-from-design, based on biological evidence, was elaborated by William Paley in his Natural Theology (1802). It was revived in the 1990s by several authors, with a new moniker, the theory of intelligent design. In The Origin of Species (1859), Darwin advanced a scientific explanation of the design of organisms: evolution by natural selection. Organisms are pervaded by imperfections, dysfunctions, cruelties, and even sadism. The theory of evolution accounts for these mishaps, by natural selection, so that they need not be attributed to God's explicit design. The theory of evolution by natural selection is Darwin's gift to religion, in addition to its centrality in biology.
    Teleological argument
    Argument (complex analysis)
    Creationism
    Origin of species
    Intelligent design
    Charles darwin
    Citations (1)
    This chapter contains sections titled: Intelligent Design Darwin's Scientific Revolution Natural Selection Chance and Necessity: Mutation and Natural Selection "Only a Theory" Evolution Is a Fact Irreducibly Complex? The Disguised Friend References and Recommended Readings
    Intelligent design
    Scientific Revolution