412 p. S. MARTIN 



may be Important in understanding the possible hunting techniques 

 of use against the large, gregarious plains herbivores. However, as 

 Eisley (1946) noted, even the most ardent proponent of fire as an 

 ecological force may hesitate to attribute the extinction of forest 

 mastodons, the giant beaver {Castoroides) , and the West Indian 

 hystricomorphs to this technique. The mysterious survival of large 

 African herbivores frustrates sweeping conclusions. 



For paleoecological purposes it seems necessary to consider the 

 significance of large vertebrates as climatic indicators. If prehistoric 

 man is an extinction agent, how are we to interpret shifts in range in 

 terms of paleoecological uniformitarianism? Tapirs and capybaras, 

 today denizens of tropical forest, formerly ranged far to the north, 

 respectively to Oregon and Pennsylvania and to Florida and Arizona. 

 Are there compelling reasons to believe that, in the absence of man, 

 these animals would not occupy the same range under the present 

 climate? 



The porcupine, opossum, and armadillo have notably extended 

 their ranges within historic time. The opossum and armadillo moved 

 northward (Guilday, 1958; Fitch et at., 1952), the porcupine south- 

 ward, into Sonora (Benson, 1953). These extensions can be at- 

 tributed to climatic change. They can also reflect the reoccupation 

 by these species of marginal positions in their former range, from 

 which they had been eliminated in prehistoric time by human preda- 

 tion. The mountain top populations of Marmota flaviventris in 

 southern Arizona, New Mexico, and northeastern Mexico were 

 trimmed. Subalpine and boreal habitats, apparently suitable for 

 marmots, persist in these areas today. 



The giant tortoises, like the tapir and capybara, are another 

 group in which a complacent assumption of tropicality is read into 

 their ranges, for example, by Crook and Harris (1958, p. 241). Sur- 

 vival of tortoises only on remote oceanic islands seems to be at- 

 tributable to the circumstance that they here escaped pre-Columbian 

 extermination by man rather than to climatic change. Assumptions 

 of climatic change based on the present distributions of relatives of 

 the late Pleistocene fossil vertebrates are gratuitous as long as an 

 alternate cause of extirpation is possible. In brief we may inquire 

 whether tropical forests and remote islands constitute refugia from 

 climatic change or from the hunting practices of prehistoric man. 



For sensitive indicators of climate and past environments it may 



