By identifying stable isotopes of carbon-12 in human tissue

By identifying stable isotopes of carbon-12 in human tissue, scientists have been able to prove that 25% of all carbon molecules consumed by Americans originate in corn. One of the most ubiquitous substances in the North American diet, corn has seemingly innumerable, multifarious uses. Each corn kernel’s endosperm contains a preponderance of starch, a substance made of glucose molecules connected by glycosidic bonds which create long and complex chains of carbohydrate molecules that scientists have learned to separate and rearrange to form crucial raw materials for food and other industries. In the form of cattle feed, corn provides the key ingredient in the production of cheap meat, the basis of the contemporary American diet, while high fructose corn syrup is the major component of carbonated beverages so popular in the West. It could be argued that the current American way of life is not imaginable without the abundant supply of this staple crop. Therefore, given the multitude of corn’s benefits unlocked by modern technology, it is ironic that an earlier culture equally dependent on it for sustenance might have been severely hampered by its limitations.

According to most scientists, corn is a mutated descendent of teosinte, a wild grass native to Central America. The ears of the teosinte plant were not large, encased the seeds in a hard envelope and contained much less seed than comparable grains, making them unappealing to primitive humans. However, several thousand years ago, an evolutionary jump redesigned the teosinte. The tassel, the male inflorescence at the end of a primary lateral branch of the plant, underwent a feminization which monopolized the resources of the lateral branch, creating larger ears with a corresponding number of seeds with higher nutritional content.

This evolutionary path is, according to anthropologist Jared Diamond, a key to the condition of pre-Columbian American societies. While Eurasian societies had an abundance of wild grains available for cultivation and, therefore, moved to agriculture tens of thousands of years ago, a time period which allowed for the creation of large populations and, eventually, a market for advanced technologies, pre-Columbian Americans had no enticement to form agricultural societies. They made this move relatively late and therefore had no time to create societies as large and complex as the Europeans, a fact that led to their defeat when the latter arrived in Central America.

Diamond’s argument is not only innovative and parsimonious but relies on a seemingly unassailable basis of our knowledge of the evolutionary biology of corn. However, historical considerations make one reluctant to accept the veracity of Diamond’s elegant argumentation. Whenever they started to grow, as we now know, Central American societies achieved significant demographic growth and technological progress and were able to mobilize significant resources for the conduct of war. Therefore, one must seek the roots of their defeat not in their dependence on corn but in factors such as epidemics launched by European arrival and the political dissensions in their midst.

Which of the following, if true, would weaken the author's objections to Diamond's theory?

(A) Although the population of pre-Columbia America was decimated by disease, the armies arrayed against the Europeans did not suffer the same fate because they did not live in close quarters.
(B) While they were outnumbered, the Europeans' use of iron breastplates allowed them to withstand the impact of bronze-tipped arrows used by pre-Columbian Americans.
(C) Remains of pre-historic agricultural societies in Eurasia show evidence of sophisticated technologies at much higher levels that those achieved by American societies at the time.
(D) Some societies of pre-Columbian American were strong enough to enforce their will on their neighbors and drew on those resources to present a united front against a third party.
(E) The average size of a pre-Columbian America village and the average yield of its crops were only half as large as their European counterparts.