140 



Franz J. Kallmann 



In line with clinical and psychological observations, it is 

 shown by comparative data on the length of life of senescent 

 twins (Table I) that basic variations in the human lifespan 

 depend on gene-specific health and longevity potentials. In 

 those pairs of our sample where both twins died after age 60, 



Table I 



BlENNTAL MEAN INTRA-PAIR LIFESPAN DIFFERENCES IN SAME-SEXED TWIN 



PAIRS OVER 60 



* Significant at 1% level 

 ** All opposite -sexed pairs over 60: 106.0 months 



the mean intra-pair lifespan difference continues to be much 

 smaller in one-egg than in two-egg pairs. The present total 

 mean difference varies from 36 • months in the one-egg group 

 to 74-6 months in the two-egg group of the same sex, and to 

 106-0 months in dizygotic pairs of opposite sex. In same- 

 sexed pairs, this difference is about the same for both sexes, 

 despite the shorter lifespan of the male. It may also be 

 mentioned that one-egg twin partners are more than twice as 



