1.Introduction: Definitions, Background -- 2.Competition For Limiting Resources, Hamilton's Rule And Chesson's R* -- 3.Flexible And Derived Varieties of Mammalian Social Organization: Promiscuity In Aggregations May Have Served As A Recent g2sToolkitg3s Giving Rise To g2sSexual Segregationg3s, Polygynous Social Structures, Monogamy, Polyandry And Leks Abstract -- 4. Multimale-Multifemale Groups And g2sNestedg3s Architectures: Collaboration Among Mammalian Males -- 5. Higher g2sGradesg3s Of Sociality In Class Mammalia: Primitive Eusociality -- 6. Ecological Models As Working Paradigms For g2sUnpackingg3s Positive And Negative Interactions Among Social Mammals -- 7.Mechanisms Underlying The Behavioral Ecology Of Group Formation -- 8. The Evolution Of Mammalian Sociality By Sexual Selection -- 9. Proximate Causation: Functional Traits And The Ubiquity Of Signaler To Receiver Interactions: From Biochemical To Whole Organism Levels Of Mammalian Social Organization -- 10. Synopsis

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 g2stool-kitg3s. "Top-downg3s (predators to nutrients), as well as g2sbottom-upg3s (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 g2snorms of reactiong3s (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 g2sdecisionsg3s made by types responding to competition for limiting resources constrained by Hamilton's rule (inclusive fitness operations)