428 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1944 
not necessarily indicate any great degree of antiquity. When such 
occurrences are in deposits that can be correlated with geologic phe- 
nomena, attributable to the late Pleistocene, however, dating the as- 
semblage as of that time is justifiable. Some of the North American 
evidence indicates that the earlier migrants were in the New World 
at the end of that period and on the basis of certain interpretations of 
the Patagonian manifestations it would appear that some must have 
arrived well before its termination. 
To describe in detail the different implements comprising the various 
complexes and those occurring in sporadic assemblages of bones and 
artifacts has not been possible in the bounds of the present discussion. 
It may be said that there are examples suggestive of late Paleolithic 
tools, a few Mesolithic forms, and numerous early Neolithic types. 
Comparisons are frequently made between these implements and those 
from various European stone industries. This is misleading, however, 
as the American examples must have been derived from eastern Asia 
where the development of stone working was for the most part inde- 
pendent of that in Europe. Such similarities to European types as 
may occur have no chronological significance and should not be used 
as criteria for dating New World material. 
There has been considerable disagreement and much argument over 
the date of the arrival of the first immigrants from Asia.’ This situa- 
tion may be attributed to the basing of conclusions on such differing 
factors as the characteristics of the archeological material, the faunal 
assemblages, the nature of the human skeletal remains, and the geologic 
evidence. The latter as a rule is considered as being the most accept- 
able, and dates based on it are now regarded by many as substantially 
correct. Without going into the problems of glacial variations and 
synchronization, varve counts, fossil pollens, and related subjects, it 
will suffice to say that from these sources the ages of various phenomena 
have been determined. The opening of the corridor east of the 
Rockies, making migration southward from Alaska possible, has been 
placed at 15,000 to 20,000 years ago. There appears to have been a 
similar opening some 20,000 years earlier, but it is generally considered 
as being too ancient to have played a part in human activities. The 
termination of the last pluvial in the North American Southwest, 
which is important in the study of a number of the manifestations, has 
been dated at approximately 10,000 years ago. The Lindenmeier site 
in northern Colorado is dated at from 10,000 to 25,000 with the state- 
ment that it may have been nearer the 25,000 mark (Bryan and Ray, 
1940), although other authorities consider the 10,000 figure as more 
nearly correct (Sayles and Antevs, 1941, p. 41, note 29). The Black 
Water Draw, between Clovis and Portales, N. Mex., has been dated 
12,000 to 18,000 (Antevs, 1935a). The oldest level of the Cochise is 
