Amarathus is a related genus of plant and was actually domesticated by the Paleo Indians in North America.
Archeoblog includes this article that discusses if North American Indians went from gathering the seeds while hunters to actually domesticating the seeds as a crop.
awhile back, I checked an article on PaleoIndians in the NE of North America which said the archeologists could identify when this was domesticated because the size of the grain in their archological digs got larger, i.e. men (or more likely women) we selecting the larger seeds to plant for a future crop.
But it seems that at one point, corn was introduced, and corn gives you a lot more calories so the seeds were no longer grown for a major food crop, although it did supplement the diet.
Sort of like when I worked in Africa: Most of the dietary calories were from corn meal mush, and corn was introduced by the Portuguese, but most people had a small field of millet or sorghum because it will give a crop if the rains are poor, and they also use it to make beer... and we often advised them to use this to feed their malnourished babies because it was easier to digest than maize.
There are lots of Amaranth species out there, and Wikipedia lists a lot of different folks that use it for food all over the place.
a foodie discusses the Amaranth vs quinoa here, and includes recipes.
and pigweed is an amaranth that is pesticide resistant and you've probably seen it growing in your garden or in the local vacant lot.
The leaves, stems and seeds of Palmer amaranth, like those of other amaranths, are edible and highly nutritious. Palmer amaranth was once widely cultivated and eaten by Native Americans across North America, both for its abundant seeds and as a cooked or dried green vegetable. Other related Amaranthus species have been grown as crops for their greens and seeds for thousands of years in Mexico, South America, the Caribbean, Africa, India, and China.
The plant can be toxic to livestock animals due to the presence of nitrates in the leaves. Palmer amaranth has a tendency to absorb excess soil nitrogen, and if grown in overly fertilized soils, it can contain excessive levels of nitrates, even for humans. Like spinach and many other leafy greens, amaranth leaves also contain oxalic acid, which can be harmful to individuals with kidney problems if consumed in excess,.
the Perdue Famine food website has quite a few amaranth species listed
So remember, preppers, in case of a zombie apocolypse, pigweed is all over the place.