Switchovers and crossovers: “What’s Left?” July 2018, MRR #422

Every elementary schoolchild knows that, after 1492, two food staples common to the “New World” were introduced into the “Old World” via the trans-Atlantic exchange inaugurated by Columbus. I’m talking about potatoes and corn, or maize. What’s not so well known is that maize was substantially undigestible, that potatoes contained low level toxins, and that native Americans processed both heavily in order to make them palatable. Plant breeding and hybridization techniques since 1492 have resulted in far more edible varieties of both maize and potatoes, at the cost of the diversity of the original plant populations.

Both maize and potatoes are considered species complex (superspecies, species aggregate) which, biologically, means a group of closely related species that are so similar in appearance to the point that the boundaries between them are frequently unclear. In fact, the original maize and potato superspecies each contained hundreds, if not thousands of related individual species that could potentially hybridize. One species of maize or potato might not be able to easily cross breed with another species of maize or potato at the far range of their respective genetic spectrums, but that spectrum did allow for gradual, continuous hybridization along the way.