Before revision:  We show that ageing contains both a stochastic component, related to regulatory error accumulation in transcription/translation/metabolic pathways , and a strong deterministic component, which can be naturally associated with a part of a development programme.
After revision:  We show that ageing contains both a stochastic component, related to regulatory error accumulation in transcription/translation/metabolic pathways due to imperfection of signaling cascades in the network and of responses to environmental factors. We also establish that there is a strong deterministic component, which can be naturally associated with a part of a development programme.