MAN AS A MAKER OF NEW PLANTS — ANDERSON 465 



The cultivated grain amaranths (known to the Western world 

 mainly through such bizarre late-summer annuals as love-lies-bleed- 

 ing) demonstrate that we shall be in for some rude shocks when we 

 make serious studies of these apparently trivial plants. J. D. Sauer 

 found (1950) that this whole group was domesticates, divisible into 

 several different species, none of which could be equated to any wild 

 amaranth; that the whole group was of American origin; and that 

 the varieties cultivated since ancient times in Kashmir, China, and 

 Tibet were not (as had previously been taken for granted) derived 

 from Asiatic amaranths. They are instead identical with those cul- 

 tivated by the Aztecs and the Incas. 



It is now becoming increasingly clear that the domestication of 

 weeds and cultivated plants is usually a process rather than an event. 

 None of them rose in one leap from the brain of Ceres, so to speak. 

 The domestication of each crop or weed went on at various times and 

 places, though by bursts rather than at a regular rate. For many 

 it still continues. Our common weed sunflowers, for example, are at 

 the moment being bred into superweeds. In California, by hybridiza- 

 tion with a rare native sunflower, these weeds are increasing their 

 ability to colonize the Great Valley (Heiser, 1949). In Texas 

 (Heiser, 1951), by similar mongrelizations with two native species, 

 they are adapting themselves to life on the sandy lands of the Gulf 

 Coast (see figs. 1, 2, and 3). 



The story of the American sunflower is significant because it demon- 

 states the kinds of processes that went on in the Stone Age and 

 before, when our major crops were domesticated. It is because the 

 domestication of weeds and cultivated plants (using the word "do- 

 mestication" in its broadest sense) is a continuing process that it came 

 to my professional attention. Thirty years ago I started out to study 

 (and if possible to measure) such evolution as was still going on. As 

 I analyzed example after example, the fact became increasingly clear 

 that evolutionary activity is concentrated in (though by no means 

 confined to) disturbed habitats — to times and places where man's 

 interference with the prehuman order of things has been particularly 

 severe. Post-Pleistocene evolution, it seems, has been very largely the 

 elaboration of weedlike plants and animals. 



Now why should this be ? What is there about the presence of man 

 that stimulates his plant and animal companions into increased evolu- 

 tionary activity? A growing body of observational and experimental 

 data bears directly upon that question ; rather than summarizing it, 

 let me describe in considerable detail one particularly illuminating 

 example. It concernes the hybridization of two California species 

 of wild sage, Salvia apiana and S. mellifera. They have been meticu- 

 lously studied by Epling — in the field (1947), the herbarium (1938), 



