BOTANICAL MUSEUM LEAFLETS 
HARVARD UNIVERSITY 
Marcu 10, 1959 Vor. 18, No. 8 
Campringr, Massacuusetts, 
THE ORIGIN OF CORN 
II. Tkostnre, 4 Hysrip or Corn anp Tripsacum 
BY 
Rozpert G. REEVEs AND Paut C. MANGELSDORF 
THE tripartite theory of the origin of corn (26) holds, 
among other things, that teosinte (Zea mexicana) origi- 
nated as a hybrid between corn and Tripsacum, which 
backcrossed to corn one or more times. In 1939, the 
hybridization was postulated as having occurred well 
after corn had been domesticated, perhaps as late as 900 
A.D. Reeves, however, later (35) favored the sugges- 
tion of Stebbins (47) that it might have occurred much 
earlier, possibly at a time when corn and Tripsacum pos- 
sessed somewhat the same plant characters as now but 
when they were more interfertile. Mangelsdorf and 
Smith (28) reported archaeological evidence that teosinte 
came into existence not later than 500 B.C. and perhaps 
earlier. 
Both Weatherwax (51, 52,53) and Randolph (81, 32) 
raised objections to this part of the theory, objections 
which fall into the following categories: (A) A cross as 
difficult to make as that of corn and Tripsacum could not 
have occurred in nature. (B) Tripsacum chromosomes 
and genes have a negligible effect when in combination 
with corn germplasm. (C) The frequency of interchange 
or crossing over between corn and Tripsacum is not suf- 
ficient to give rise to anew intermediate species by intro- 
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