6538 



On the Tendency of Species 



varieties of a species might have a better chance of escaping or 

 protecting themselves against certain adverse circumstances than the 

 parent species; as, for instance, unusual length of limb might give an 

 antelope greater facility to escape from the feline Carnivora; and it is 

 argued that, after such a variety had become numerous, any subsequent 

 circumstances which would throw an additional strain on the vitality 

 of such species would result in the annihilation of the parent, leaving 

 only this variety, which is assumed to be a superior variety. 



Now have we any right to assume that an antelope with longer legs 

 than its parent is superior to that parent? It seems evident that we 

 cannot, in any way, do so, unless we are certain that it has every other 

 power and faculty in the same perfection as its parent, and is exposed 

 to no other disadvantage on account of this partial superiority, and 

 I cannot think there is sufficient ground for such an assumption ; the 

 additional speed which would enable it to escape from some enemies 

 might be accompanied with dulness of sight or hearing, which would 

 leave it more exposed to the attacks of others, and in all probability 

 it would be accompanied by a thinner coat, which would render it 

 more susceptible to changes of temperature, and by a necessity for 

 more food, which would throw an additional strain on its other powers, 

 and these and other circumstances of a similar nature would counter- 

 balance the partial superiority supposed ; and even if not, — even if any 

 variety thus specially characterized should, under certain circum- 

 stances, acquire a numerical superiority over the parent species, — is 

 there any reason to suppose that a subsequent change of circumstances 

 would throw an additional weight into the scale in favour of the 

 variety ? I think not. The perfection of any organized being con- 

 sists in its unity as a whole — in its adaptation to all the phases of its 

 being ; and a special modification in one direction, to meet certain 

 circumstances, so far from rendering it more suited for different cir- 

 cumstances, would in all probability produce an opposite result. 



But it will probably be objected that this is all very inconclusive ; 

 and so it is, and so must all our opinions on this subject be till we 

 are far wiser than we are now. The fact seems to be that there is, 

 among organized beings, a tendency to vary ; but a tendency is not a 

 law of indefinite progress ; a tendency to increase is not a law of 

 indefinite increase, neither is a tendency to vary a law of indefinite 

 variation. Tendencies can be seen in their true light only when 

 viewed in connexion with other tendencies which modify and set 

 limits to them ; and if, as in the present case, we know something 

 more of one tendency than of the opposing ones, we have not, on that 



