Flaws in the theory of predictive adaptive responses.

Human foetuses have been proposed to make 'predictive adaptive responses' during pregnancy, to adapt metabolic profile in anticipation of conditions expected in adulthood. Predictive adaptive responses are invoked in particular to explain associations between early-life experience and risk of the metabolic syndrome, although the concept is problematic on theoretical grounds and fits poorly with empirical data. In ecosystems, as in economics, the future cannot be predicted with confidence. It is likely to be the case that human offspring look not to the future but back to the past, and align their developmental trajectory with maternal phenotype, the key factor in determining their nutritional supply. This debate has important implications, potentially offering a robust theoretical basis for designing public health interventions and guiding the nutritional management of individual infants.