QUATERNARY 68 1 



plements are left, especially along river courses where the pebbles 

 from which the implements were made occur. 



(2) If a stone implement is found buried to a great depth, the 

 thickness of the overlying deposit has often been taken as a measure 

 of its age. Such data are very uncertain, since during floods a river 

 may scour out deep holes in its bed, and within a few weeks, or months, 

 completely fill the excavation. The Missouri, for example, scours 

 out its bed to a depth of 40 feet or more during floods, and soon fills 

 it again (p. 88). It will readily be seen, therefore, that the finding 

 of a flint implement in river gravels at a depth of 40 feet might not 

 indicate any greater antiquity for it than for one on the surface. 



(3) The age of flints in talus slopes is uncertain, since what was in 

 the top portion of the cliff naturally becomes part of the base of the 

 talus as the clifF crumbles back. 



(4) The antiquity of stone implements found beneath layers of 

 stalagmite has often been overstated, because a too low rate of deposi- 

 tion was used in the estimate. This, however, has not been a source of 

 difficulty in America, since cave deposits are rare on this continent. 



(5) The admixture of human remains with those of extinct animals 

 is not necessarily a proof of their contemporaneousness, since it may 

 have been due to accidental causes, such as human burial in deposits 

 containing extinct animals, or to the washing out from older deposits 

 of the bones of extinct animals and their redeposition with those of 

 recent species. 



It will readily be seen from the above that the error in determining 

 the age of human relics will usually be in the direction of too great 

 antiquity. From the similarity in physical appearance of the aborig- 

 ines of North and South America, it seems probable that the original 

 inhabitants of the New World were immigrants who came from Asia 

 and spread over the Americas after they had become differentiated 

 in Asia, but long enough ago to permit of the development in their new 

 home of the many languages and dialects now spoken by the Indians. 



REFERENCES FOR MAN IN NORTH AMERICA 



Osborn, H. F., — Age of Mammals, pp. 494-500. 



Osborn, H. F., — Men of the Stone Age. 



Scott, W. B., — A History of Land Mammals in the Western Hemisphere, pp. 588-590. 



Wissler, C, — The Art of the Cave Man : Am. Museum Jour., Vol. 12, 191 2, pp. 289-295. 



Birthplace of Man. — The location of the original home of man was 

 a matter of speculation even by the ancients and is still in doubt, bur 



