"Teosinte is a wild grass, which is closely related to maize. In fact, it is generally considered the ancestor of modern maize and has been recovered from cave sites in Oaxaca, Mexico occupied by humans as long as 4000 years ago.....
The teosinte that can be found in farmer’s fields today is generally a hybridized form of teosinte. Teosinte found in Mexico is about 95% fertile with maize; Guatemalan teosinte is about 85% fertile with both maize and Mexican teosinte. This means that the Guatemalan teosinte has higher sterility and is likely an earlier form.
Hybrid clusters in fields can be attributed to a common parent that outcrossed in the previous year. An isolated teosinte plant surrounded by maize has a higher probability of outcrossing. If maize pollen and teosinte pollen reach the teosinte silks at the same time, often the teosinte will win."
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