This brief discusses factors associated with group formation, group maintenance, group population structure, and other events and processes (e.g., physiology, behavior) related to mammalian social evolution. Within- and between-lineages, features of prehistoric and extant social mammals, patterns and linkages are discussed as components of a possible social tool-kit . "Top-down (predators to nutrients), as well as bottom-up (nutrients to predators) effects are assessed. The present synthesis also emphasizes outcomes of Hebbian (synaptic) decisions on Malthusian parameters (growth rates of populations) and their consequences for (shifting) mean fitnesses of populations. Ecology and evolution (EcoEvo) are connected "via" the organism s norms of reaction (genotype x environment interactions; life-history tradeoffs of reproduction, survival, and growth) exposed to selection, with the success of genotypes influenced by intensities of selection as well as neutral (e.g. mutation rates) and stochastic effects. At every turn, life history trajectories are assumed to arise from decisions made by types responding to competition for limiting resources constrained by Hamilton s rule (inclusive fitness operations)."

Among the unresolved topics in evolutionary biology and behavioral ecology are the origins, mechanisms, evolution, and consequences of developmental and phenotypic diversity. In an attempt to address these challenges, plasticity has been investigated empirically and theoretically at all levels of biological organization-from biochemical to whole organism and beyond to the population, community, and ecosystem levels. Less commonly explored are constraints (e.g., ecological), costs (e.g., increased response error), perturbations (e.g., alterations in selection intensity), and stressors (e.g., resource limitation) influencing not only selective values of heritable phenotypic components but, also, decisions and choices (not necessarily conscious ones) available to individuals in populations. Treating extant mammals, the primary purpose of the proposed work is to provide new perspectives on common themes in the literature on robustness ("functional diversity"; differential resistance to "deconstraint" of conserved elements) and weak robustness (the potential to restrict plasticity and evolvability), plasticity (variation expressed throughout the lifetimes of individuals in a population setting "evolvability potential"), and evolvability (non-lethal phenotypic novelties induced by endogenous and/or exogenous stimuli). The proposed project will place particular emphasis upon the adaptive complex in relation to endogenous (e.g., genomes, neurophysiology) and exogenous (abiotic and biotic, including social environments) organismal features discussed as regulatory and environmental perturbations with the potential to induce, and, often, constrain variability and novelty of form and function

Reproductive skew is the study of how reproduction is partitioned in animal societies. In many social animals reproduction is shared unequally and leads to a reproductive skew among group members. Skew theory investigates the genetic and ecological factors causal to the partitioning of reproduction in animal groups and may yield fundamental insights into the evolution of animal sociality. This book brings together new theory and empirical work, mostly in vertebrates, to test assumptions and predictions of skew models. It also gives an updated critical review of skew theory. The team of leading contributors cover a wide range of species, from insects to humans, and discuss both ultimate (evolutionary) and proximate (immediate) factors influencing reproductive skew. Academic researchers and graduate students alike with an interest in evolution and sociality will find this material stimulating and exciting.