Up to now, there are no wild materials, fossils or even intermediate types in the process of maize domestication from wild to cultivated in nature.
Maize is a kind of "super" domesticated crop, which has lost the most basic characteristic of other crops-the ability of natural reproduction, that is, maize reproduction must rely on artificial transmission before species can reproduce.
Who is the wild ancestor of corn, and how did the ancient Indians domesticate corn into such an advanced crop? Understanding the origin and evolution of maize is of great reference value for explaining the origin and evolution of maize and even the whole plant species.
In the past two centuries, many scientists have made unremitting explorations on maize ancestors and their evolution from the perspectives of morphology, cytology, archaeology and molecular biology, and put forward many theoretical hypotheses about the origin of maize, which are summarized in this paper (note: Mr. Liu's Maize Breeding summarizes some theoretical hypotheses about the origin of maize before the 1980s).
The hypothesis of the origin of wild corn with barnyard grass was put forward by Saint-Hilaire 1829.
According to this hypothesis, corn originated from the original wild corn with skin. The present corn has no shell and thick bracts outside the ear, which is the result of long-term domestication and selection.
This theory comes from a special ear of corn obtained by Saint Hilaire from Brazil. Each ear is covered with glumes, similar to oak and oats, and the whole ear is covered with bracts. This kind of wild corn is different from modern cultivated corn (table 1).
The hypothesis of "three-component origin" by Mangers Doff and Reeves also regards primitive wild corn as the primitive natural wild type of corn.