No, it is not easy. In fact, a large majority of tests have failed in the ITP. But you are right about the major role of “extraneous” environmental factors, an

No, it is not easy. In fact, a large majority of tests have failed in the ITP. But you are right about the major role of “extraneous” environmental factors, and this is why we started our studies with a systematic perturbation of diet—low fat versus very high fat (citations are above). The correlation of longevity on these profoundly different diets is about r = 0.6 based on an analysis of 76 balanced cohorts of strains on the two diets—about 10 females per strain per diet. With the deep replication (10 identical twins per treatment) these are rock solid data. A correlation of 0.6 gives “explained variance” of only 36% (r^2), so that highlights the major effect of diet on longevity. And the gene variants that modulate longevity on the two diets are, as expected, very different. Bottom line: the genetics of longevity is the genetics of gene-by-environment interaction—your major point.