The Biology of Senescence 



Hereditary factors in human longevity have often been 

 sought. Pearl and Pearl (1934a, b) found, for instance, that the 

 summed ages at death of the six immediate ancestors of centen- 

 arians and nonagenarians were significantly greater than in a 

 control series of the relatives of individuals not selected for 

 longevity. 86-6 per cent of long-lived (> 70) subjects had at 

 least one long-lived parent, while 48-5 per cent of nonagenarians 



60- 



60 



: 40 



u 



20 - 



i i i i I i i i i i I i i i i iir'r ff'l | <"i 



24 monfhl 



Fig. 31. — Survival curves of mice in laboratory culture — breeding females. 



Curve A based on 241 dba females, curve B on 730 Bittner albinos, curve C, 



on 1350 Marsh albinos (from Gruneberg, 1951). 



and 53-4 per cent of centenarians had two such parents, all 

 these figures being significantly higher than in the control series. 

 Kallman and Sander (1948, 1949) found that in 1062 pairs of 

 twins the mean difference in longevity between dizygotic twin 

 individuals was twice as great as in monozygotics. These and 

 other studies indicate that longevity is 'hereditary', but un- 

 fortunately give little light on its genetics. Beeton and Pearson 

 (1901) studied the longevity records of Quaker families, and 

 found that the sib-sib correlation of longevity was nearly twice 

 the parent-offspring correlation, in those individuals who died 



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