An overview from Existence is Wonderful: "So, what is known so far about longevity in mole-rats and echidnae? Well, perhaps not as much as is known about mice, but certainly a fair amount - and the pool of knowledge is growing all the time. ... One theory regarding exceptional longevity in mammals [is] the "membrane pacemaker" theory of metabolism ... Essentially, what this means is that some findings suggest a relationship between metabolic rate and the health over time of the various fatty-acid membrane structures that comprise animal physiology. Animals are, in a sense, made possible by membranes - life is dependent upon being able to direct functional pathways along specific routes, and to contain chemical materials where they are needed (that is, where they can perform their life-sustaining activities). Longer-lived species, according to the membrane pacemaker theory, are likely to have more peroxidation-resistant membrane lipids than shorter-lived species ... naked mole-rat membrane structure actually remains largely unchanged with age, but that the chemical composition of mole-rat membranes more lipid-peroxidation-resistant than that found in mice."