302 I The Process of Evolution 



In the 90 years following the writing of this passage biologists have 

 been rather well disabused of the idea that species are unchange- 

 able, but the idea that they are "things" lying in wait to be discov- 

 ered in nature lingers on. 



There may be an additional cultural factor tending to prevent 

 recognition of anything but neatly segregated animal entities in 

 nature. There is a revulsion against so-called "miscegenation" in 

 many parts of Western culture. It has been suggested that, although 

 it is considered permissible for plants to engage in iUicit activities 

 (hybridization), such behavior could not be recognized in animals. 

 The validity of this interesting speculation is, to say the least, diffi- 

 cult to evaluate. There can be little doubt, however, that cultural 

 factors strongly influence the biologist's view of the structure of 

 nature. 



If the generalization that organisms exist as distinct species is 

 largely invalid, does this mean that there is no practical way of 

 investigating the diversity of nature? At first glance, it might seem 

 that the current nomenclatural structure would be an insuperable 

 obstacle to reasonably objective description of the patterns of vari- 

 ation found in the earth's biota. However, as long as names are 

 viewed merely as convenient landmarks in the continuum of life, 

 rather than as possessing some deep (if obscure) meaning in them- 

 selves, the problems are not too serious. 



In recent years taxonomists have been investigating multivariate 

 methods of assaying similarities among organisms. These techniques 

 rely on high-speed, automatic, data-processing equipment to com- 

 pare simultaneously many features of organisms or groups of or- 

 ganisms and to express numerically the degree of similarity of each 

 entity in the study with every other entity. For instance, it is easily 

 within the capabilities of modern digital computers to compare 200 

 different butterflies with each other, each of the 19,900 individual 

 comparisons being based on 100 or more attributes of the individuals 

 compared. Such computing systems obviously have a capacity that 

 transcends that of the human mind for making relatively objective 

 multiple comparisons. The details of the techniques are beyond the 

 scope of this book, but an introduction to the field of numerical 

 taxonomy is provided through a single brief example and in the 

 references at the end of this chapter. 



Development of these techniques for comparing organisms should 

 be of considerable aid in solving some of the more vexing questions 

 about the evolutionary process. Methods have been developed that 

 mathematically and pictorially express the patterns of relationship 

 found in numerical taxonomic studies. In this way, a portion of the 



