One of the most characteristic and widely observable features of senescence, usually ignored by scientific investigation, is a very variable, dapple distribution of its manifestations, seen within systems, organs, and tissues of the same individual. Different parts of an organ or tissue undergo senescence at different ages. The early aged foci may form only small solitary places in a tissue, an organ, a region, or an organism or in large parts of it. The proportion of early aged parts to later aged ones, as well as their localization, is predestined by individual genetic makeup, thus determining diversity in the course and forms of senile regression and the lifespan of organisms under consideration. It is a kind of biodiversity that is least known. To clear up what we can say about the nature of the phenomenon today, the features of this kind of human body diversity were interpreted using the data and conceptions of immunology, molecular biology and genetics. The results of the interpretation allow us to suppose that different parts of a human body usually have unequal genetic limits of life duration and their own programs of ageing; each of them has its own 'biological watch' which tells a different time. The genesis of this diversity can be explained by hybridization of persons with different genetic susceptibility to internal and/or environmental factors inducing senescence.