RELATION OF LIFESPAN TO BRAIN WEIGHT 

 AND BODY WEIGHT IN MAMMALS* 



George A. Sacher 



Division of Biological and Medical Research, 

 Argonne Natioiial Laboratory, Lemont, Illinois 



My interest in the comparative study of lifespans stemmed 

 from the reahzation that the zoological literature contains a 

 wealth of data that can be used to analyse the factors govern- 

 ing ageing and longevity in mammalian species. In this paper I 

 shall first describe a statistical analysis of the relations of life- 

 span to brain and body weight, and then enter into a discus- 

 sion of the theoretical issues. These considerations have been 

 alluded to briefly in previous communications (Sacher, 1957, 

 1958). 



The objective of the empirical analysis is to establish the 

 quantitative dependence of the lifespans of mammalian 

 species on the body weights, brain weights, and metabolic 

 rates of adult representatives of these species. This is in effect 

 a study of allometric relationships, in which lifespan is regarded 

 as a physical dimension of a species on the same footing as the 

 linear or mass dimensions. In this paper the species lifespan 

 is defined as the maximum documented longevity for that 

 species. With a few exceptions the lifespan data come from 

 domesticated animals or from zoo animals. 



There were two reasons for using the lifespan rather than 

 the life expectation. The first is that satisfactory estimates of 

 the life expectations even now are available for only a few 

 domesticated species and for an even smaller number of 



* This work was performed under the auspices of the U.S. Atomic Energy 

 Commission, 



115 



