Understanding the evolutionary history of crops, including identifying wild relatives, helps to provide insight for conservation and crop breeding efforts. Cultivated Brassica oleracea has intrigued researchers for centuries due to its wide diversity in forms, which include cabbage, broccoli, cauliflower, kale, kohlrabi, and Brussels sprouts. Yet, the evolutionary history of this species remains understudied. With such different vegetables produced from a single species, B. oleracea is a model organism for understanding the power of artificial selection. Persistent challenges in the study of B. oleracea include conflicting hypotheses regarding domestication and the identity of the closest living wild relative. Using newly generated RNA-seq data for a diversity panel of 224 accessions, which represents 14 different B. oleracea crop types and nine potential wild progenitor species, we integrate phylogenetic and population genetic techniques with ecological niche modeling, archaeological, and literary evidence to examine relationships among cultivars and wild relatives to clarify the origin of this horticulturally important species. Our analyses point to the Aegean endemic B. cretica as the closest living relative of cultivated B. oleracea, supporting an origin of cultivation in the Eastern Mediterranean region. Additionally, we identify several feral lineages, suggesting that cultivated plants of this species can revert to a wild-like state with relative ease. By expanding our understanding of the evolutionary history in B. oleracea, these results contribute to a growing body of knowledge on crop domestication that will facilitate continued breeding efforts including adaptation to changing environmental conditions. Introduction Results - Sequencing Depth and SNP Identification - Phylogeny and Population Clustering Distinguish Wild and Feral Populations - Species Tree and Admixture Inference Indicate Brassica cretica Is the Closest Living Wild Relative - Archaeological and Literary Evidence Point to a Late-Holocene Domestication - Late-Holocene Environmental Niche Modeling Highlights Wild Relatives’ Ranges Discussion - Multiple Lines of Evidence Support a Single Eastern Mediterranean Origin - The Role of Ferality in the Domestication of Brassica oleracea - Postdomestication Cultivar Relationships Materials and Methods - Taxon Sampling - RNA Isolation and Sequencing - Mapping and SNP Calling - Phylogenetic and Introgression Inference - Population Structure and Variation - Clustering Based on Expression Profiles - Environmental Niche Modeling