The term "bloodlines" is used in dog and livestock breeding to refer to recognisable ancestral groups, often initiated or created by a single breeder or kennel, and nearly always the product of a significant degree of inbreeding, along with their present-day descendants. Traditionally the name of the breeder or the kennel affix is used as an identifying label when referring to such bloodlines. The term is a legacy of horse breeding and dates from a time before the exact mechanism of heredity was known to science and was thought to be inherent in the blood of an animal.