DO THE FASTEST CONCEPTI HAVE A SHORTER LIFE-SPAN

An evolutionary hypothesis based on an 'antagonist pleiotropy' or 'dis posable soma' mechanism is put forward to explain differences in longe vity between species, strains, and sexes, Data from several congenic m ouse strains and mammalian species suggest that there may be an associ ation between cleavage rate of concepti and longevity, in such a way t hat concepti from species, strains or the sex (male) with the fastest cleavage rates have shorter life spans. The major histocompatibility c omplex (MHC) and, in particular, the conceptus development gene (Ped) together with several Y-linked genes that are expressed during the pre implantation stages of development may play an important role in deter mining or modulating longevity in mammals, Notwithstanding, effects of other loci as well as environmental factors on conceptus development and longevity cannot be ignored.