and Hawkes (25), regard as *‘preadaptation.’’* These authors 
stress the fact that primitive ancestral forms of successul culti- 
vated plants already possessed tendencies which induced man 
to cultivate them. Corn had its share of these especially in its 
easily harvested and threshed grain, and its conspicuous re- 
sponse to man’s ministrations: freedom from competition with 
other vegetation and increased soil fertility. Early cultivators, 
although perhaps noting corn’s large pollen grains, just visible 
to the naked eye, could scarcely have been aware of their 
significance. But it was its large pollen grains that gave corn the 
ability to evolve in the direction of producing larger and larger 
ears. If ever there was a wild species preadapted to domestica- 
tion, corn is perhaps the prime example of this condition. 
Teosinte does not have this preadaptation: it could not have 
evolved in this direction without a series of mutations involving 
pollen size. 
POSSIBILITY OF CONTAMINATION 
One recent explanation of the fossil pollen is that it repre- 
sents contamination (/), either from modern pollen at the upper 
levels being carried to a lower one during the sampling or from 
pollen in the air when the sampling was being done. To explain 
the fossil pollen as contamination is, of course, to assume that 
it is indeed corn pollen. 
That pollen in the | - 3 meter level could be carried down to 
the 69.2 - 70.5 meter level leaving no contamination at interven- 
ing levels seems quite improbable, if not impossible, in view of 
the precision of the equipment and the techniques employed in 
“Further reading has shown us that the idea of preadaptation as presented by these 
authors, is new only as it applies to evolution under domestication. Simpson in his 
book, Tempo and Mode in Evolution (Columbia University Press, 1944) discusses at 
length the concept as it applies to evolution in nature. Students of corn’s evolution, 
including the senior author of the present article, have perhaps been remiss in not 
recognizing the phenomenon of preadaptation as an important factor in corn’s amaz- 
ingly rapid evolution under domestication. Included among corn’s preadaptive charac- 
teristics is its ability to hybridize and exchange genes with its relatives, teosinte and 
Tripsacum, Teosinte lacks this characteristic, since, if it is cultivated corn’s only 
ancestor, it had no wild corn, Zea Mays, with which to hybridize and its does not, even 
under ideal experimental conditions, hybridize successfully with Tripsacum. 
246 
