So what did Amerindians in North America eat before corn was introduced?

There is a concept called the Colombian exchange, about the exchange of crops, technology and diseases that followed Columbus and other European invaders/settlers.

But there is an almost unknown history of Native America before then... and alas too many Youtube etc stuff is nonsense, missing the real history.

Here is a lecture series on PaleoIndians, stressing the Nothern continent.



one of the newer ideas is that they might not have trudged down between glaciers, but came along the coast, (where artifacts might have been lost as the sea rose).

the northern tribes eventually obtained corn from the south, but by that time they had already started domesticating other crops, such as sunflower, gourds, and grains. LINK

Over several thousand years, selective collection and seed deposition on middens by sedentary foragers would have had the same impact as selective breeding done by scientists today: genetic modification of the plant community. In patches of disturbed soil at the Archaic Period campsites, the seeds deposited by humans would not have been from "average" plants. Those plants would have had larger-than-average seeds, more-than-the-average-quantity of seeds on each plant, more-than-average percentage of seeds that would ripen at the same time, and more-than-average percentage of seeds that would cling to the plant after ripening.
...In the Western Hemisphere, plants were domesticated in Eastern North America separately from the development of agriculture in Central and in South America. Domestication of three species occurred in the Mississippi Valley - and perhaps in Virginia as well, though the archeological evidence is documented primarily from sites in the Ohio/Tennessee/Mississippi River valleys.2 three of the first native plants to be domesticated for food in North America: Marshelder (Iva annua) Sunflower (Helianthus annuus)Lambsquarters (Chenopodium berlandieri)

eventually corn made it there, and became the main crop.

NYT article on the 9000 year history of corn (Maize).

what is interesting is that corn didn't just spring up and then man made it larger: Corn originates in a plant that does't look anything like corn...

teosinte vs. corn after 9,000 years of human selection
Source: National Science Foundation, Scientists Trace Corn Ancestry from Ancient Grass to Modern Crop

Early cultivators had to notice among their stands of plants variants in which the nutritious kernels were at least partially exposed, or whose ears held together better, or that had more rows of kernels, and they had to selectively breed them. It is estimated that the initial domestication process that produced the basic maize form required at least several hundred to perhaps a few thousand years.

more HERE.

And then there is the story of the turkey:
domesticated in two areas (SW US and Mexico) and initially used for feathers. but only were raised as a major food source later.

Domestic turkeys were initially raised for their feathers; however, around 1100 A.D., Native Americans began to rely on these birds as a food source.

COURTESY OF THE AMERIND FOUNDATION, INC., DRAGOON, ARIZONA. ERIC J. KALDAHL, PHOTOGRAPHER

but the ones we eat today are mainly from the Aztec ones...