We have seen how the theory of PARs helps us to understand the aetiology of some of the common chronic diseases of adulthood, especially components of the metabolic syndrome (Syndrome X), which include high blood pressure, Type 2 diabetes, a disordered blood-lipid profile and clotting-factor levels, obesity and increased risk of atheroma, coronary heart disease and stroke. Such diseases have a high prevalence in the developed world and are increasing at an alarming rate in populations in transition in the developing world. The humanitarian and financial burden they convey is enormous. The growing epidemic of obesity in young people further magnifies the problem.

But what of other common chronic diseases – breast and prostate cancer, asthma, Alzheimer's disease? Is it possible that the biological phenomenon of PARs could underlie the aetiology of such diseases? We can only speculate. For each of these conditions there is some evidence but as yet it is either preliminary or unconfirmed, so we felt that it would not be responsible to include it in our discussions at this stage.

Not everything that happens in early life and has lifelong consequences is a result of PARs. Teratogenesis is an irreversible developmental disruption which can have no predictive or adaptive value. In addition, some responses the fetus must make to survive (e.g. preterm delivery in the face of amniotic infection) must have inevitable costs after.