Technical Abstract: The presence of mammary glands are the defining morphological feature of mammals, and a successful lactation is crucial to mammalian reproductive strategies. Among mammalian species, the nature of lactation and the composition of milk vary greatly. The evolution of lactation and its diversity among species is of considerable interest to biologists. Recent assembly of the bovine genome has expanded the capability of agricultural biologists to investigate this economically important species and the opportunity for comparative study of mammalian genomes. The evolution and diversity of lactation are briefly discussed in this article in context of a current publication in Journal of Biology dealing with the linkage of bovine milk and lactation data with other mammalian genomes.