ARCHEOLOGY AND ECOLOGY OF ALASKA — SOLECKI 473 



the emergence of a land bridge between Asia and America. That 

 this was not improbable is shown by several facts. Only some 56 

 miles of water separate both continents today, with a couple of is- 

 lands between the narrowest point. The minimum recession of 

 sea depth necessary for reemergence of the bridge is only about 120 

 feet. Furthermore, a true land bridge would have been required 

 to allow the intercontinental exchange of so many fauna. It may 

 be assumed as a possibility that as the animals migrated into the 

 New World, the first Americans and their successors followed. The 

 first or earliest Americans are collectively distinguished by the title 

 of "Early Man" or "Paleo-Indian." It is certain that all animals 

 did not have equal opportunities for reaching the intercontinental 

 highway, nor were all equally equipped with or adapted to the neces- 

 sary survival qualities, as George Gaylord Simpson (1940) has pointed 

 out. This type of screening may be termed a "filter bridge" (fig. 

 2). Early Man undoubtedly crossed into the new continent unknow- 

 ingly, with no preconceived notions of exploration and followed 

 the unglaciated portions of America. His route was presumably 

 controlled by the topography and the extent of the dispersion of 

 game. 



We assume that the first American, principally a hunter of herbi- 

 vores — like the carnivores of the region — was more interested in the 

 larger grass-eating mammals. The latter, in turn, depended on the 

 existence of suitable fodder. We feel that man did not consciously 

 direct his traffic in one direction or another but expanded his terri- 

 tory with the dispersion of his game. Thus, the usual definition of 

 migration with a view to residence does not strictly apply here. 

 Douglas Leechman (1946, p. 386) aptly states: 



Diffusion would be a better term than migration. In all probability, the first 

 people to cross the Bering Strait, and to make America their permanent home, 

 camped not very far from their landing place.^ Gradually the surrounding 

 district beca.me known to them and, as a result of hunting expeditions in the 

 neighborhood, attractive camp sites and fishing stations would be discovered. 

 As their children grew up, and had families of their own, they would settle a 

 few miles farther upstream or inland, thus diffusing gradually throughout the 

 whole district. The movement of an amoeba by means of pseudopodia gives us 

 an excellent illustration of the type of migration involved. 



It may be objected that this is altogether too slow a process, but an average 

 of as little as two miles a year would carry people from the Yukon down to 

 the bottom of South America in approximately 5,000 years. 



Leechman's estimate may be a little too conservative when we con- 

 sider some of the archeologically known shifts of populations in 

 America. It is also apparent that the process was not quite so simple. 



• Evidently Leechman bylicves that Early Man established a beachhead, crossing over water and not a 

 land bridge. This may have been true for man, but not for other mammalian life. Present-day travels 

 of Eskimos between the two continents by boat are well known. 



