Generations: birth to reproductive maturity. An average human generation is twenty-two years. (Norman, 7/14/09) A single step in the line of descent from a common ancestor. (NCIt) The offspring of the same parent or parents. The whole body of people born or living at about the same time; later also, the average length of time in which children become ready to take the place of their parents. (Oxford)

Atavistic: resemblance to more remote ancestors rather than parents; tendency of animals to revert to an ancestral type. (Oxford)

Consanguinity: genetic relatedness between individuals who are descendants of at least one common ancestor. (NCIt) Marriage between blood relatives. The term means ‘shared blood.’ (Lewis, 76) The magnitude of ‘inbreeding’ in humans. (MeSH)

First Generation: the first generation born (in a country or an environment). (Brooker, 328) Editor's note - inheritance nomenclature is ‘F1’ Also referred to as ‘first filial.’

Lineage: organisms allied by common descent. (Lawrence) Descent in a line from a common progenitor or source. (NCIt) The genetic relationship between an individual or group of individuals and its ancestors. A series of ancestors in a population that shows a progression of changes. (Brooker, G-21)

Origin: the beginning, cause, or ultimate source of something; that from which a thing is derived. A person's parentage, or ancestry. (Oxford) The place where something begins or comes from in either the sense of a physical location or a metaphysical source. (NCIt)

Second Generation: the second generation offspring. (Brooker, 328) Editor's note - inheritance nomenclature is ‘F2’  Also referred to as 'second filial.’