(A) The fraction of modern 14C present in the membrane lipids of human lens nuclear regions. The lipid samples (•) are superimposed over the levels of artificial 14CO2 present in the atmosphere in the northern hemisphere (light gray) and the southern hemisphere (dark gray) from 1950 until 1990 (Hua et al., 2013). (B) The correlation between the predicted year of birth as calculated from the measured fraction of modern 14C present in lens membrane lipids and the actual year of birth of each individual. The slope was approximately one (0.98 ± 0.04) and the y-intercept was indistinguishable from zero within the measured error (39 ± 75). Vertical error bars: ± sigma. Horizontal error bars: year of birth ± six months.