346 NATURAL SCIENCE. mav. 



of food or tissue, or to other slight advantages, may carry child or 

 man through fevers otherwise fatal, or through physical dangers and 

 hardships, or arduous labours and mental trials under which he would 

 otherwise have succumbed. In the not very remote past, a lighter 

 skull, by diminishing the weight to be moved, and so increasing a 

 man's speed and agility, may have enabled him to save his life by 

 flight from enemies, or to overtake and kill a less swift and agile foe. 

 Considering correlated changes and advantages, and looking at the 

 many and varied tests through which our species has had to pass, at 

 the critical episodes of personal strife, the occasional narrow escapes 

 from natural dangers, and the innumerable diseases, parasites, 

 microbes, &c., that waylay us through life, and search out the weaker 

 points, it becomes almost impossible to say that any advantage has 

 been so minute as never to have affected survival. Under starvation, 

 wounds, disasters, illnesses, men hover on the brink of the grave, 

 and a hair's-breadth of advantage, a single grain of spare nutriment 

 or lessened expenditure, may decide ultimate recovery, while any 

 little disadvantage may prove the last straw that breaks the camel's 

 back. All organisms pass through kindred dangers and diseases of 

 which we know little and care less. As a rule, the lower animals 

 suffer far more frequently and severely from starvation and enemies 

 than man does ; they multiply much faster, and they are eliminated 

 with proportional frequency. In view of such facts, we are by no 

 means bound to suppose that small economies can never influence life 

 or death in their immediate or ultimate effects. 



Darwin did not disdain to call in the effects of slight causes. He 

 partly attributes the somewhat reduced size of our teeth to the prin- 

 ciple of economy,'- although a tooth is scarcely ^^uooth part of the 

 weight of a man's body. Mr. Spencer, however, thinks that we 

 ought to feel certain that economy, panmixia, and reversed selection, 

 all put together, cannot reduce the useless, exposed, and sensitive 

 eyes of the proteus and other "blind fish and amphibia" living in 

 dark caves. We are told, indeed, that " an economy of ^o^h of the 

 creature's weight could not appreciably affect survival " (p. i66).'3 

 But if Natural Selection were really incompetent to secure economy 

 in small parts, it could not secure economy in the body as a whole. 



i'^ Descent of Man, p. 562. 



'•'' Such an economy is equivalent to the saving of three-quarters of a pound in 

 man. Many circumstances are concei\able in which death might be avoided and 

 muhiplication be fa\'Oured by sHghtly increased faciHty and quicl<ness of motion, 

 by surplus nutriment, and lessened Habihty to various dangers. Disused parts 

 retain, or, apparently even increase, their share of liability to tumours, ulcers, and 

 other diseased conditions which occasionally prove fatal by their direct or indirect 

 results — of which many examples are known in man, the only animal with 

 whose pathology we are really well acquainted. Probably, too, as Ray 

 Lankester points out, there was a preliminary selection of animals whose im- 

 perfect eyes led them into the sheltering darkness of the cave, and prevented them 

 from straying from it. 



