Evolution is the outcome of an interaction between adaptive specializations and phylogenetic constraints. In terms of learning mechanisms, the last decades have seen an emphasis on the study of adaptive specializations in learning stemming from discoveries on taste aversion and avoidance learning made during the 1960s. The adaptive approach has been presented as the only biologically plausible by some proponents. However, both empirical evidence on learning, and major recent discoveries in evolutionary biology point to what appears to be extreme conservatism of biological processes, including learning. Learning mechanisms underlying acquisition, discrimination, and spatial memory, among others, appear to be general and based on conserved aspects of the vertebrate telencephalon. There is, however, evidence of an evolutionary divergence in vertebrate history that points to the evolution of emotionally-mediated processes in instrumental learning in the lineage leading to the mammals. Adaptation and conservatism appear to be both essential to understand the evolution of vertebrate learning processes.