Journal of Heredity 10(4): 170-172. (1919)
A FOSSIL EAR OF MAIZE
First Tangible Evidence of the Existence of Indian Corn in Geologic Times
G. N. COLLINS
Bureau of Plant Industry, United States Department of Agriculture, Washington, D. C.
|1 Jour. Wash, Acad. of Sci., Vol. 9, No. 5, pp. 134-136, March 4, 1919.|
DR. F. H. KNOWLTON has recently published the description of a fossil ear of maize from Peru.1 The specimen, which is described as a new species, Zea antiqua Knowlton, was purchased from a collector of curios in Cuzco, Peru, in 1914. In spite of its unsatisfactory history, the specimen is of especial interest since it affords the first tangible evidence of the geological existence of this important cultivated plant.
It is well known that maize or Indian corn was grown widely in North and South America before the time of Columbus. How long before, there is as yet no way of determining. A very long period is indicated by the fact that the progress made in the improvement of this plant since the discovery of America is insignificant in comparison with the changes that must have taken place since the prototypes of maize were able to exist as wild plants. Not only were the kinds found growing by the earliest explorers similar to those now cultivated, but remains of ears found in prehistoric graves are almost duplicates of the varieties grown in the same regions today.
The finding of a fossil ear means that the origin of maize may now be transferred from prehistoric to geologic times, for Dr. Knowlton is confident that, although the specimen may not be assigned to its exact geological period, it is an undoubted fossil. Yet the type it represents is domesticated maize essentially like the varieties still being grown in Peru and Bolivia.
Mexico is generally thought to be the region where maize was originally domesticated. The chief reason for assigning the origin of maize to Mexico rather than to South America is the important fact that Mexico is the natural habitat of teosinte, the nearest wild relative of maize. On the other hand, the great diversity of types existing in South America certainly bespeaks either a very great antiquity or a multiple origin.
|2 Darwin, C. R., "Geological Observations on Coral Reefs, Volcanic Islands and on South America," Pt. II, pp. 47-49, London, 1851.|
Prior to the discovery of Zea antiqua the most ancient evidence of maize was the specimens found by Darwin2 who unearthed "heads of Indian corn," mixed with marine shells and earth on an elevated ledge on the island of San Lorenzo near Callao, Peru. The ledge on which the relics of maize were found was elevated 85 feet above sea level. The shells which accompanied the maize specimens belonged to recent species and were covered with a few inches of detritus. Darwin states that the maize and human remains "had all indisputably been embedded with the shells."
The ear of Zea antiqua is 60 mm. long and 35 mm. in greatest diameter. The apical portion is missing but the original ear must have been about 80 mm. in length. The butt is rounded and the ear is strongly tapered, there being no portion even approximately cylindrical.
FOSSIL MAIZE AND MODERN MAIZE
|An ear of fossil maize (Zea antiqua) compared with existing South American types. Nos. 1, 2 and 3, different aspects of the fossil ear; No. 4, a Bolivian variety from high altitudes; Nos. 5 and 6, a Peruvian popcorn from Ollantaytambo; Nos. 7 and 9, Copacabana variety from near Lake Titicaca; No. 8, a Peruvian variety called Granada. (Fig. 7.)|
The seeds are from 4 to 8 mm. in length and from 3 to 5 mm. in width, sharply pointed and irregularly disposed. The seeds on one side of the ear at some distance from the base are somewhat smaller and more irregular in form, making the ear slightly asymmetrical. Asymmetry of this kind is frequently observed in varieties which have the ears closely oppressed to the culm. If this analogy is correct, the aspect shown in Fig. 7, No. 1, is the axial side of the ear. The articulation of the seeds with the cob can be readily made out and individual seeds are easily detached. The structure of the cob is not apparent, at least without sectioning. The seeds extend around the base indicating that the pedicel must have been very small. In size and shape the specimen is similar to the ears of Peruvian and Bolivian varieties, illustrations of which are shown with those of the fossil ear in Fig. 7.
The gradually rounded butt is not an uncommon character and is well illustrated in Nos. 4, 5 and 7. The shape of the seeds cannot be exactly duplicated by any specimen in our collection, but is not unlike those of a Peruvian variety of pop-corn shown as No. 5 that was grown near Ollantaytambo. Pointed seeds are a common characteristic of Bolivian and Peruvian varieties, but they are usually much larger than those of Zea antiqua. An example of these larger pointed seeds is shown as No. 8. The irregular arrangement of the rows is approximated by specimens of the Copacabana variety from the region of Lake Titicaca, No. 7.
The extent to which the base is covered by the seeds seems almost to preclude the possibility of a pedicel able to hold the ear in an upright position. Equally small pedicels are, however, not uncommon in Peruvian specimens. See Nos. 6 and 9. In existing varieties having very small pedicels, the pedicels are also short and the ear is supported chiefly by the subtending leaf-sheath.
While the fossil ear is not duplicated by any ear in our collection, it presents no new characters, but rather a different combination of characters found among the existing types.