EVOLUTION OF MAN 249 



taboos, as, for example, in Hawaii, Jamaica, and many other parts of the 

 world, racial hybridization is frequent and biologically normal. It is upon 

 this basis that we conclude that all living peoples belong to one species. 



Parenthetically it will be well to note a dissenting opinion on the state- 

 ment just made. As we shall see in our discussion of classification (pp. 

 314-320), the "biological definition" of the word "species" given above is 

 not accepted by everyone. Dift'erent species usually diff"er structurally, as 

 well as in the matter of reproductive isolation. If one stresses structural dif- 

 ferences and minimizes the importance of reproductive isolation one may 

 conclude that the different races are so different structurally that they 

 should be considered separate species. From time to time various students 

 of human evolution have adopted this view (see Gates, 1948), but most 

 investigators conclude that all modern peoples belong to but one species. 



Turning our attention to the prehistoric men, we ask: how should they 

 be classified? As noted previously, Cro-Magnon man has long been con- 

 sidered a member of our species, sapiens. In addition we have noted 

 earlier peoples (such as Swanscombe, Steinheim, Ehringsdorf, and Fonte- 

 chevade ) who had so many sapiens-Yike attributes that placing them in our 

 own species seems justified (Le Gros Clark, 1955, 1959). Actually we can, 

 of course, have no direct knowledge of the matter of reproductive isolation in 

 their cases, but structurally they were so like typical sapiens that repro- 

 ductive isolation from the latter seems unlikely. 



As we have seen, some of the Pleistocene peoples combined Neanderthal- 

 like characteristics with sapiens-like ones. What shall we say of them? 

 Would they have been reproductively isolated from their more sapiens- 

 like contemporaries? And what of the typical or "classic" Neanderthal peo- 

 ples themselves? Would they have been reproductively isolated from peo- 

 ples combining Neanderthal-like and sapiens-Wke characteristics, and from 

 sapiens-Uke people? We can not answer these questions with certainty. 

 As noted previously, classic Neanderthals are usually placed in their own 

 species on structural grounds, and called Homo neanderthalensis. But per- 

 haps all these late Pleistocene men constituted "actually or potentially 

 interbreeding natural populations" and hence should be considered mem- 

 bers of but the one species. Homo sapiens (Mayr, 1950). 



And what of the various forms that collectively we have called Pithe- 

 canthropus, living in earlier Pleistocene times? They are so unhke Homo 

 sapiens that they are usually placed in a separate genus {Pithecanthropus) 

 from him, though, as noted previously, Mayr ( 1950) suggested that the dif- 

 ferences are not sufficient to warrant separation at the species level, and 

 suggested Homo erectus as a suitable name. 



Going back to the earliest Pleistocene we find still less agreement con- 



