Natural selection implements an efficient mechanism for the invention of adaptive structure and function, including sexual selection, which plays a role in creating sex-linked traits. These selective pressures can potentially divide a population into fractions with diversified anatomy and behavior, which can even lead to speciation. The morphological and neurobehavioral traits subsequently change in such events, and although the significance of this coordinated change for evolution is obvious, the underlying mechanisms remain an enigma. Consider the case of Homo sapiens. The use of language and tools and the trait of self-actualization/self-awareness/consciousness are uniquely human, and the emergence of these neurobehavioral traits is believed to be tightly coupled with changes in the skeletal organization and entire body structure. However, little is known about the mechanism underlying such “body (morphological)–mind (neurobehavioral)” concordance.
Thus, despite an explosion of Evo-Devo studies on morphological traits, the impact of neurobehavioral factors upon speciation has been almost completely ignored. This issue of the Journal of Neurogenetics features review articles from a number of experts to highlight seminal studies using systematic analyses of diversification in the neural circuitry in relation to genomic changes that led to polymorphic behavioral traits within and among populations. I would like to name this emerging research field “Evo-Devo-Neuro-ethology.” I believe that the Evo-Devo-Neuro approach to behavior will pave the way for understanding how selective forces drive diversification in genetically constrained behavioral traits by researching into rare mutations that renovate brain operation while maintaining its vital functions. It will thus unveil a unified mechanistic basis for how natural selection and sexual selection coordinate to shape a behavioral phenotype by acting through vital and nonvital life channels. The featured articles forecast an accelerated growth of the Evo-Devo-Neuro ethology, which is expected to create a new horizon in evolutionary biology.