The Theory of Evolution | 301 



The biological-species concept might be redefined in a way that 

 would make laboratory tests conclusive; the problem of cutting the 

 continuum of possible degrees of success in hybridization would 

 remain. In addition, the amount of work involved in delimiting a 

 single species would be staggering, and one would still be faced with 

 the omnipresent problem of the experimental biologist: deciding 

 what the experimental results tell him about situations in nature. 



Considering the patent difficulties of dealing with the concept of 

 species, how can one account for its great tenure in the biological 

 literature? The idea seems to have had its origins in western Euro- 

 pean parochialism. As in the bear example in Chap. 11, the apparent 

 distinctness of clusters is much enhanced when only a small geo- 

 graphic area is known. Equally, inadequate sampling over a large 

 geographic area will increase the impression of distinctness. If an 

 expedition from Mars collected samples of man by shooting a few 

 inhabitants of Norway and one or two African pygmies, the Mar- 

 tians might easily come to the conclusion that there were two dis- 

 tinct species of man. 



The appearance of Darwin's Origin of Species signaled the end 

 of the idea that species were eternal and unchanging but did rela- 

 tively little to dispel the notion of prevalence of distinct clusters. 

 However, the idea that scientists, in expecting to find discrete spe- 

 cies, were imposing their own prejudices on nature was not entirely 

 lost on biologists of the last century. J. Victor Carus (Geschichte 

 derZoologie, 1872) stated: 



It is of interest to note that in Aristotle the difference between plants 

 and animals is already touched upon. . . . Regarding the nature of some 

 marine growths one may be in doubt whether they are plants or animals. 

 . . . Even the ascidians, says Aristotle, properly may be called plants 

 since they cive off no excrement. . . . One sees that Aristotle fell into 

 the same error as almost all moderns. The term "plant," which came to 

 us as part of our language, was interpreted as a term that must correspond 

 to a class of naturally occurring entities. The same thing has happened to 

 later workers with respect to the term "species." Instead of investigating 

 whether there exists in nature anything that is unchangeable and circum- 

 scribed and that corresponds to this term, and then, in the absence of 

 such, to allow nature her liberty and only artificially to assign a meaning 

 to it that corresponds to the current state of knowledge, one simply 

 assumed that one was compelled to consider the words as a symbol for 

 one of nature's secrets, a secret that one might still hope to unveil.^ 



^ We are indebted to Prof. R. G. Schmieder for translating this passage and 

 bringing it to our attention. 



