By Val Giddings
Thomas Jefferson famously noted that “[T]he greatest service which can be rendered any country is to add a useful plant to its culture…” Outgoing Mexican President Andrés Manuel López Obrador (AMLO) did not get that memo.
At AMLO’s direction, on 13 February 2023, the Government of Mexico published a decree purportedly aimed at enhancing Mexican food security and sovereignty. The decree “prohibits the use of genetically modified corn for dough and tortillas” and directs health authorities to “carry out scientific research into the possible impacts of genetically modified corn on people’s health.” These measures are undertaken allegedly to safeguard the integrity of indigenous breeds of corn and to evaluate whether or not “genetically modified” corn threatens human health. The decree also reaffirms the Government of Mexico’s responsibility to ensure “that phytosanitary decisions must be based on scientific evidence.”
In view of the multiple factual errors in the decree the United States, appropriately, objected and requested consultations in Geneva to discuss the conflict between the decree and Mexico’s obligations under WTO rules. But in the interval, reality has inconveniently intruded, leading to AMLO subsequently pausing his proposed ban on “GMO” corn.
Then on June 2, Mexico elected Claudia Sheinbaum to succeed AMLO. Formerly the mayor of Mexico city, and hand-picked by AMLO, Sheinbaum is a physicist and atmospheric scientist who has promised to continue the populist policies of AMLO’s Morena party. Despite a blemished record as mayor, her reputation as a pragmatist has led to high hopes in some quarters that some of AMLO’s anti-science policies might be repaired.
The extent of historical human manipulation of maize genetics is so extensive that half of the genes in modern corn are derived from non-maize lineages, mostly of viral origin. These sequences have been drivers of maize evolution, and a Nobel Prize was awarded to Barbara McClintock for beginning to figure out what was going on. The genes show us that corn is far from a “natural” plant (what “natural” means is a topic for another day). It is, in fact, a purely human artifact, the intended result of thousands of years of genetic manipulation by smallholders in what is now Mexico, who are some of the most successful informal innovators in human history.
The ancestor from which modern corn is descended is a species of grass that is actually something of a weed in southern Mexico and Central America: teosinte. Plant geneticists have long debated vigorously the exact relationship between teosinte and maize, and a clear picture has now begun to emerge thanks to modern molecular techniques. The essential facts are clear – the indigenous stewards of heirloom varieties of maize actively hybridized them among each other, saving and maintaining results they liked and discarding those they didn’t. Fifty years ago, researchers collected at least 59 distinct landraces from one Mexican state. The true number from the entire country is unknown, but undoubtedly much larger. The most important finding from all this research is just how dynamic the stewardship of these myriad varieties has always been. The informal innovators who have been growing these ever-changing varieties for the past 9,000 years swapped their genes back and forth in every way imaginable. Were it not for the propaganda campaigns of professional opponents posing as ‘green’ their certain response to news of a maize variety resistant to pests would be to plant some, cross it with their preferred varieties, and work with the results to develop new and more desirable varieties, as they’ve done forever. Indeed, there is some indication that the process may already be underway.
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