The integrity and health of an organism can be considered as a state actively imposed by specialised 'salutogenic' mechanisms (immune, endocrine, paracrine etc) on an innate tendency towards internal conflict. One major source of internal conflict arises from the operation of natural selection upon replicating sub-organismal components such as cells, organelles and gene sequences. From this perspective cancer is seen not as a pathological process arising in a healthy organism but as caused by the capacity of replicating cells to evolve 'selfish' adaptations and elude the finite repertoire of integrative mechanisms. Cancer can therefore be regarded as one instance of a more general tendency towards senescence due to the failure of salutogenesis and accumulation of endogenous parasites. This may provide a new and potentially fruitful approach to framing, analysing and understanding the aetiology of the degenerative diseases of senescence.