Thin ground sections of first molars (M1), third molars (M3), and second premolars (P2) were scanned by light microscopy for relative amounts of interglobular dentine (IGD) in the top half of the crown. Two well-dated cemetery series of English provenance were sampled: the Saint Bride's Church collection (SB) from eighteenth century London, for which the sex, age, and calendar year at death of each individual are known; and the early Anglo-Saxons from Abingdon (A-AS), near Oxford. A lesser number of prehispanic aboriginal Guanche teeth from Tenerife (TG) were also studied. Estimates of insolation in the past were developed indirectly by reference to delta 0(18) mass spectrometer analyses of dated layers of the Greenland ice sheet. In the M1 and M3 of the SB and the A-AS populations, IGD varied as an inverse linear function of average annual hours of bright sunshine below a certain critical level, the insolation deficit threshold being significantly higher and IGD formation faster in the M1 than in the M3. No such dose-response gradient was apparent in the P2 data, presumably because the calcification of this tooth during the fourth year of life coincides with serious pediatric illnesses and weaning of the child onto cereal foods rich in phytate, which together confound and overwhelm the insolation deficit effect. IGD in all three types of teeth of the small TG series was considerably higher than had been predicted on the basis of bright sunshine availability; but the discrepancy is readily explainable in terms of this population's dietary, which relied on barley as the main staple.