PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 413 



be necessary to consider only plant distributions plus those small 

 animals whose population density and reproductive capacity could 

 keep pace with human predation. 



Within our present knowledge there seems little agreement on the 

 problem of extinction and man's role in it. Most authors who have 

 reviewed the problem reduce it to the outcome of an interaction of 

 all factors that can limit animal populations — predation, competi- 

 tion, parasitism, climatic change, evolutionary lag during environ- 

 mental stress, and also the effect of man (Colbert, 1938; Gill, 1955; 

 Hamilton, 1939; Osborn, 1906; Romer, 1945; Simpson, 1931, 1953). 

 I believe this multiple hypothesis does injustice to the temporal 

 and ecological record, i.e., (1) differential loss of large animals, (2) 

 lack of evidence of major climatic change during the extinction 

 period, (3) the narrow chronological range in which extinction oc- 

 curred, and (4) the phenomenon of removal without replacement. It 

 would appear that within the Cenozoic the late Pleistocene environ- 

 ment had some unique features. Man is the only one clearly 

 identified. 



Acknowledgments 



In part the viewpoints expressed grew out of seminars and less formal 

 discussions on Pleistocene matters at the universities of Michigan, Yale, 

 Montreal, and Arizona. In particular I would thank the following for their 

 help: P. Dansereau, M. B. Davis, E. S. Deevey, J. A. Elson, R. F. Flint, 

 F. K. Hare, B. E. Harrell, E. W. Haury, J. J. Hester, C. W. Hibbard, 

 K. F. Koopman, J. F. Lance, A. and D. Love, C. H. Lowe, G. Lowther, 

 M. Martin, J. E. McDonald, J. E. Mosimann, J. G. Ogden, G. B. Rabb, 

 J. Schoenwetter, T. L. Smiley, and D. R. Whitehead. Mrs. Helen Griffin 

 provided valuable clerical aid. I am indebted especially to palynologists 

 F. H. Barclay, M. B. Davis, E. B. Leopold, and D. A. Livingstone, who 

 forwarded advance copies of their unpublished pollen diagrams. 



REFERENCES 



Aguayo, C. G. 1950. Observaciones sobre mamiferos cubanos extinguidos. 

 Bol. hist, natural soc. Felipe Poey, 1: 121-134. 



Allen, G. M. 1911. Mammals of the West Indies. Bull. Museum Comp. 

 ZooL, 54: 175-263. 



. 1918. Fossil mammals from Cuba. Bull. Museum Comp. ZooL, 



62: 133-148. 



. 1942. Extinct and Vanishing Mammals of the Western Hemisphere. 



American Committee for International Wild Life Protection, Lan- 

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