An account of the origin of turkeys is presented. The development of the turkey, including comparisons with other poultry species, is covered in a review of research published on turkey genetics and breeding from the 1920s to 1987. The subject has been divided into the following topics: gene mutations, cytogenetics, biochemical assessments, physiological assessments and parthenogenesis, strain and variety comparisons for body characteristics, body conformation, body weight, efficiency of feed utilization, egg production, semen production, sexual maturity, fertility, hatchability, egg weight, yield of edible meat, and phenotypic deformities. The review is in two parts. Part I, which follows, covers origin and development while Part II, covering economics and selection, will appear in the next issue, volume 45:2 (July, 1989)