much light on this, the data presented here in no way 
conflict with multiple and independent origins for Amer- 
ican agriculture. Archaeological evidence seems at pres- 
ent to support this hypothesis and may be expected to 
add important information in the future (19, 20, 86, 181). 
Some writers (9) have upheld a very great antiquity for 
New World agriculture. The information on this is yet 
fragmentary, but here too, the joint efforts of archaeology 
and botany are doing much to clarify the picture and 
indicate a quite respectable age for agriculture in this 
hemisphere (19, 131). 
With attention being focused on the ultimate origins 
of agriculture, more thought is being given to the man- 
ner in which plants first entered cultivation. However, 
less is being heard of the ingenious savage who decided 
to return seed or roots to the soil and thereby revolution- 
ized culture overnight (I suspect that early man had an 
adequate understanding of the seed long before he used 
this knowledge in agriculture). It seems more probable 
that the development of agriculture, whatever its pat- 
tern, was a gradual process. Some authors (9, 10, 176, 
178, 205, 206) have drawn attention to the weedy ‘‘camp- 
follower’’ element among our cultivated plants, those 
plants which might be expected to invade camp sites and 
trash heaps and to be encouraged by man. The hypo- 
thesis of a gradual development from such a nearly com- 
mensal relationship has much to recommend it. The al- 
liance was probably never purely commensal, but to some 
degree mutualistic or symbiotic from the beginning, with 
both members profiting from the association. Instances 
of semi-cultivation in peripheral areas of North America 
are described elsewhere (42), and several are known for 
tropical America. A considerable number of New World 
cultivated plants are such ‘‘weedy’’ types and many are 
still to be found on the trash heap; such plants include: 
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