Phenotypic plasticity plays a crucial role in driving genetic evolution by enabling populations to adapt to new environments. The review explores how phenotypic plasticity interacts with environmental conditions to produce genetic change, using a model of an adaptive landscape. Moderate levels of plasticity are optimal for population survival and allow populations to shift towards new adaptive peaks. High levels of plasticity may increase population persistence but reduce genetic change, as the population becomes close to an adaptive peak. Moderate plasticity arises when multiple traits, some plastic and others not, form a composite trait involved in the adaptive response. For example, altered behaviors may drive selection on morphology and physiology. Phenotypic plasticity is widespread in nature and may speed up, slow down, or have little effect on evolutionary change. Moderate levels of plasticity may often facilitate genetic evolution, but careful analyses are needed to determine whether plasticity is essential or incidental to population differentiation. The review uses two examples from birds: the evolution of red and yellow plumage coloration due to carotenoid consumption and the evolution of foraging behaviors on islands. Carotenoids are responsible for many bird colors, and their availability influences plumage coloration and subsequent genetic evolution. Foraging behaviors also evolve in response to environmental changes, with behavioral changes often leading to morphological and physiological evolution. Phenotypic plasticity can drive genetic change through a process called genetic assimilation, where plastic responses become genetically fixed. This process is illustrated in experiments with Drosophila and birds, showing how plastic responses can be genetically assimilated over generations. The review concludes that moderate levels of phenotypic plasticity are optimal for evolution in novel environments. Plasticity enhances population persistence and places populations under directional selection towards new peaks. However, the term "moderate" is context-dependent, and plasticity may be essential, facilitative, or even detrimental to adaptation. Future research is needed to determine the likelihood of each scenario in nature. The study highlights the importance of phenotypic plasticity in shaping evolutionary trajectories, particularly in behaviors and morphological traits, and underscores the complex interplay between plasticity and genetic evolution.Phenotypic plasticity plays a crucial role in driving genetic evolution by enabling populations to adapt to new environments. The review explores how phenotypic plasticity interacts with environmental conditions to produce genetic change, using a model of an adaptive landscape. Moderate levels of plasticity are optimal for population survival and allow populations to shift towards new adaptive peaks. High levels of plasticity may increase population persistence but reduce genetic change, as the population becomes close to an adaptive peak. Moderate plasticity arises when multiple traits, some plastic and others not, form a composite trait involved in the adaptive response. For example, altered behaviors may drive selection on morphology and physiology. Phenotypic plasticity is widespread in nature and may speed up, slow down, or have little effect on evolutionary change. Moderate levels of plasticity may often facilitate genetic evolution, but careful analyses are needed to determine whether plasticity is essential or incidental to population differentiation. The review uses two examples from birds: the evolution of red and yellow plumage coloration due to carotenoid consumption and the evolution of foraging behaviors on islands. Carotenoids are responsible for many bird colors, and their availability influences plumage coloration and subsequent genetic evolution. Foraging behaviors also evolve in response to environmental changes, with behavioral changes often leading to morphological and physiological evolution. Phenotypic plasticity can drive genetic change through a process called genetic assimilation, where plastic responses become genetically fixed. This process is illustrated in experiments with Drosophila and birds, showing how plastic responses can be genetically assimilated over generations. The review concludes that moderate levels of phenotypic plasticity are optimal for evolution in novel environments. Plasticity enhances population persistence and places populations under directional selection towards new peaks. However, the term "moderate" is context-dependent, and plasticity may be essential, facilitative, or even detrimental to adaptation. Future research is needed to determine the likelihood of each scenario in nature. The study highlights the importance of phenotypic plasticity in shaping evolutionary trajectories, particularly in behaviors and morphological traits, and underscores the complex interplay between plasticity and genetic evolution.