AMAZING MAIZE

     Plants depend on a variety of helpers to spread 
their seeds around: The wind, birds, animals, 
and waterways all carry seeds from one place 
to another. Most plants get along just fine with-
out humans. Not so with corn. Corn depends 
entirely on humans to spread its seeds; 
archeological evidence confirms that corn 
has traveled only where humans have taken it. 
What’s striking about this story is that modern 
geneticists have pinpointed the mutations that 
humans took advantage of to create one of the 
world’s most widely used crops.
Primitive corn (called maize) put in its first 
appearance around 9,000 years ago. The prede-
cessor of maize is a grass called teosinte. You 
need a good imagination to see an ear of corn 
when you look at the seed heads of teosinte; 
there’s only a vague resemblance, and unlike 
corn, teosinte is only barely edible — it has a 
few rock hard kernels per stalk. Yet corn and 
teosinte (going by the scientific name of Zea 
mays) are the same species.
The five mutations that turned teosinte into 
maize popped up naturally and changed several 
things about teosinte to make it a more palat-
able food source:
 ✓ One gene controls where cobs appear on 
the plant stalk: Maize has its cobs along the 
entire stem instead of on long branches like 
teosinte.
 ✓ Three genes control sugar and starch stor-
age in the kernels: Maize is easier to digest 
and better tasting than teosinte.
 ✓ One gene controls the size and position of 
kernels on the cob: Unlike teosinte, maize 
has an appearance normally associated 
with modern corn.

Humans apparently used teosinte for food 
before it acquired its mutational makeover, so 
it’s likely that people caught on quickly to the 
change that developed. The mutations of the 
aforementioned five genes were cemented into 
the genome by selective harvest and planting of 
the new variety. People grew the mutated plants 
on purpose, and the only reason corn is so 
common now is because humans made it that 
way. The first true maize crops were planted 
in Mexico 6,250 years ago, and, as a popular 
addition to the diets of people in the area, its 
cultivation spread rapidly. Archeological sites 
in the United States bear evidence of maize 
cultivation as early as 3,200 years ago. By the 
time Europeans arrived, most native peoples in 
the New World grew maize to supplement their diet.