Evening star., 1938-10-15
OF STARS,
MEN AND ATOMS
Notebook of Science Progress
in Field, Laboratory
T. and Study.
BIZ THOMAS r. HENRY.

historically Americas CTleI dsi lCuACuh a.
crop, is to be found in the Jungles OF
Central South America, according to
report just made to the National Academy
of Sciences by Drs. P. G. Mangelsdor1
and r. G. Reeves of the Texas Agrlcul-
tural Experiment Station.
Corn was found by the earliest White
explorers as cultivated crop through
out the Americas, essentially in the form
known today. It had been domestlcateo
by the Indians from some wild graln'
but there was no trace OF this hypo-
thetical ancestor Only two grassllke
prowths remotely approached it-teosinte
in Mexico and Central America and trip
sacum. which grows through the South
ern United States southwark through
Mexico.
Neither approached very closely the
cultivated maize which seems to have
spread from two centers where two great
civilizations had been built up upon it
Peru and Yucatan. The two Texas
botanists conducted their search for the
origin of corn within the grain itself by
microscopic study of the structure OF its
chromosomes, or bundles of genes, which
are the units of heredity.
These show clearly, they report to the
National Academy, that it could have de-
scended neither from teosinte or trip
sacum. The former grass, they maintain,
actually appears to be later develop
ment from a cross between maize and
tripsacum. There are tripSacum elements
in the corn now grown in the United
States, but these apparently are only
later developments.
Thus they are forced back to an un-
known wild ancestor. There Is form
of corn which sometimes appears as a
variation, especially in crops raised by
the Indians, which is characterized by
pods around each grain. Cultivated
maize, they say, could have come from
Single gene variation from this pod
corn" BY process of elimination. they
find, the most probable site for this is
Central South America, from which it
spread to Peru.
The Texas botanists report: There is
no longer any necessity for seeking the
origin of maize in Mexico or Central
America Most of the evidence, except
its close relation to teosinte, has consist
emily pointed to Peru as the primary
center of domestication. But Peru is one
of the few places in America where pod
corn is unknown.
This may be accounted for by as
suming that pod corn has survived as
relic gene in the maize varieties of the
more primitive Indians, who, notoriously
careless in maintaining purity in their
varieties, have never practiced rigid Sc
lection against the podded characteris-
tic. but that in Peru where agriculture
reached higher stage of advancement
than elsewhere in America, selection
finally succeeded in eliminating the pod
ded gene from the population. If this
assumption is sound we might still ex-
pect to find pod corn represented in the
prehistoric Peruvian pottery where the
ancient Peruvians depicted many of their
food plants. Accordingly we began
search in the museums and finally found
faithful replica of prehistoric ear of
pod corn at the Peabody Museum of
Yale University.
although Peru was undoubtedly the
primary center of domestication of maize,
1t probably was not the original wild
habitat, for the geography and climate
Of Peru are not those under which we
should expect maize to have existed as
wild plant. 1t appears far more likely
that maize had its native habitat in the
lowlands of South America-not in the
tropical rain forest, for maize completes
poorly with tall vegetation and its seed
have no mechanism for maintaining DOR
NANCY under humid conditions, but the
forests of South America are interspersed
with rainy green savannas where an
abundance of rain is followed by dry
period. In such regions wild maize
plant might easily persist. Supporting
this assumption are found four indie
pendent historical references associating
pod corn with the Guarany Indians of
South America, or with the region which
they occupied One of these describes q
type of maize which bears it's seeds in
the tassel and which may well have been
the homozygous, earless form of pod corn.
There is no evidence in conflict with
the view that maize had but one center
OF origin. In the case of several other
crops notably beans and squashes, it
appears that domestication developed in
dependently in Peru and Central Amer
lea, but this is not true OF maize"
Once the hybridization between the
pod corn and the tripsacum took place
producing teosinte, followed by number
OF back crosses, several varieties preyi-
ously unknown in the world came into be-
ing, the two botanists believe One of
these probably was popcorn, practically
unknown in South America, but very
abundant in Mexico, where the cross
probably took place. Another was flint
corn, also unknown in South America
and which makes its first appearance in
the Pueblo region of the American South
west about the year 900 AID.
These conclusions are supported, they
report, by studies OF chromosome pecu-
liarities of the various corn varieties.