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Several people have questioned whether teosinte could be a useful grain crop
because its seed are tightly encased in a hard, woody cupulate fruitcase (image),
suggesting that ancient peoples would have been incapable of freeing the grain
from this casing (See Beadle 1978; Iltis 2000). I don't accept this argument
because I believe that these ancient Mexicans were incredibly inventive and
intelligent individuals capable of solving this problem. Moreover, they had an
incentive to find a way to use teosinte grains since teosinte has a rather large
grain compared to other wild cereals. The earliest archaeological corn, which is
some 6,000 years old, has grains that are free of the fruitcase, indicating that
selection for edible grain happened very early (Benz 2001). So if the ancient
Mexicans were using teosinte for grain, how much yield could they have obtained?
To estimate the yield of teosinte, I harvested the seed from 14 randomly
chosen plants from one of my teosinte plots on Molokai Island in 2003. I thrashed
each plant against a plastic tarp to free the loose fruitcases, and then abraded
the stems some more by hand to free seed bound tightly in the leaf sheaths. I did
not attempt to recover all the seed from each plant. If I had to guess, I would say
I might have recovered about 50% from the average plant. I recovered an average of
1030 fruitcases per plant with a range from 235 to 2471. The average yield per plant
was 36.6 grams of fruitcases with a range from 6.7 to 93.1 g. The average weight of
the fruitcases was 33.3 mg with a range of 23.4 to 37.7. This average value for
fruitcase weight is on the low end of the range for teosinte as anticipated for
teosinte of southern Guerrero (Wilkes 1967; Sanchez et al. 1998).
About half the weight of the fruitcase is composed of the grain, so the average
plant yielded 18.3 grams of grain (or flour) and the best plant yielded 46.6 g. The
yield over all of my plot was 467 kg/hectare, a value that is not too far off yields
of 1000 to 2000 kg/hectare of early US open pollinated maize varieties (Troyer and
Mascia 1999). Considering that I may only have recovered 50% of the seed, I think it
clear that teosinte, even before its "improvement," had substantial yield potential for
a wild plant.
Could teosinte provide enough yield to feed a small group of
ancient peoples? Beadle (1978) estimated that a family of five could collect a
metric ton of teosinte seed in three weeks. For a family of five to obtain 25% of their
calories from teosinte grain, would require about 0.7 metric tons of grain per year
(Hillman and Davies 1990). This translates into a 1.5 hectare plot or 40,000 plants based
on my planting density and yield. Considerably fewer plants and less space would be
required if ancient teosinte farmers recovered a higher percentage of the seed from the
plants than I did. [Undoubtedly, they were better farmers than me.] Anthropologists Kent
Flannery and Bruce Smith (letters to the author) have estimated that a community in Mexico
at the time of maize domestication would have had 25 to 50 members at most. This group
would require 7.5 to 15 hectares or 200,000 to 400,000 teosinte plants, using my data.
This is very close to Flannery's (1973) estimate of 5 to 10 hectares of teosinte to support
a group of this size. His yield estimate for teosinte was 627 kg of grain per hectare where
teosinte grew in fallow cultivated fields in Mexico (Flannery 1973). Beadle's, Flannery's
and my estimates all concur that teosinte is a high yielding plant with the potential for
a small plot to support an ancient community.
Literature Cited:
- Beadle, G. W., 1978 Teosinte and the origin of maize, pp. 113-128 in
Maize Breeding and Genetics, edited by D. B. Walden. John Wiley &
Sons, New York, NY.
- Benz, B. F., 2001 Archaeological evidence of teosinte domestication from
Guilá Naquitz, Oaxaca. Proc. Natl. Acad. Sci. USA 98: 2104-2106.
- Flannery, K. V., 1973 The origin of agriculture. Ann. Rev. Anthro. 2:
271-310.
- Hillman, G. C., and M. S. Davies, 1990 Domestication rates in wild-type
wheats and barley under primitive cultivation. Biol. J. Linn. Soc. 39: 39-78.
- Iltis, H. H., 2000 Homeotic sexual translocations and the origin of maize
(Zea mays, Poaceae): a new look at an old problem. Econ. Botany 54:
7-42.
- Sanchez G., J. J., T. A. Kato, M. Aguilar, J. M. Hernandez, A. Lopez and
J. A. Ruiz, 1998 Distribucion y caracterizacion del teocintle. Instituto Nacional
de Investigciones Forestales, Agricolas y Pecuarias, Guadalajara.
- Troyer, A. F., and P. N. Mascia, 1999 Key technologies impacting corn genetic
improvement - past, present and future. Maydica 44: 55-68.
- Wilkes, H. G., 1967 Teosinte: the closest relative of maize. The Bussey
Institute, Harvard University, Cambridge.
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