Several months ago, my Canadian informant, retired Guelph University agronomy professor Ann Clark, forwarded me an article titled “Nature’s GM Sweet Potato and the Rock from Space,” which was published in 2015 (gmwatch.org/news/latest-news/16216). In this article writer Claire Robinson addressed the intentions of British biotech entrepreneur Jonathan Jones to dismantle safety testing and assessment for genetically modified (GM) foods. He justified his agenda, arguing that nature herself genetically engineered the sweet potato. Robinson proceeded to explain why his logic is faulty.
Jones cited a paper from early 2015 which showed that genes from Agrobacterium, a soil microbe, had been found in a non-GM variety of sweet potato. Genetic engineers use Agrobacterium to convey genes into host organisms in a process called horizontal gene transfer (HGT). The paper to which Jones alluded stated that nature had long been doing genetic engineering on her own, which led him to conjecture that worries about genetic engineering performed in a lab are unwarranted.
Jones referred to an article that appeared in the journal Ars Technica, by quoting it: “Genetically modified crops? Nature got there first. The sweet potato has been genetically engineered by bacteria.” That article said that consumers worry about GM crops engineered with genes from unrelated organisms. But this paper showed “that this has occurred naturally” in the sweet potato. Those authors want their sweet potato finding to “influence the public’s current perception that transgenic crops are ‘unnatural.’”
This British genetic engineer, working with Salisbury Laboratory in Norwich, England, published an article in Nature that read, “Sweet! A naturally transgenic crop: One of the world’s most important staple crops, the sweet potato, is a naturally transgenic plant that was genetically modified thousands of years ago by a soil bacterium. This surprising discovery may influence the public view of GM crops.”
In an attempt to enlighten the masses, Jones stressed, “No clearer example can be imagined for the safety of the Agrobacterium-mediated DNA transfer process than the fact that all cultivated sweet potato genotypes carry an ancient GM event, and that the results of that event have been eaten with impunity for centuries by millions of people.”
This is where Robinson stated that the axe Jones was grinding can be summed up as an equation: “Naturally GM sweet potato = no need for GMO regulations.” Jones’s message targeted Europe’s precaution-based GMO regulations.
He kept arguing: “We have been eating the products of genetic engineering for millennia, and thus demonstrate that there is no longer (if ever there was) any rationale for intense safety scrutiny from every crop line that has arisen from use of GM methods.” Robinson countered by stating: “Scientists have known for decades that gene transfer can happen in nature, so the sweet potato discovery adds little to that knowledge.”
On her own roll, Robinson asserted that Jones failed to grasp the vital difference between this “natural” genetic engineering and what happens in the lab. The former happens over evolutionary time, and the latter happens with commercially-driven speed. Any harmful mutations caused by “natural” horizontal gene transfer – e.g., those resulting in toxic plants – “will be selected out over the long process of co-evolution of humans and their food crops.”
Robinson stated that we shouldn’t assume that the long-term “natural” HGT process was benign. Most likely, collateral damage (like poisonings) occurred along the way. We don’t know. All that is certain is that the sweet potatoes we now have passed the test of co-evolution with humans over a huge time expanse and were chosen by our ancestors and bred selectively.
As Dr. Michael Hansen of Consumer Union said at the time the sweet potato paper was published, “The notion that this natural engineering of sweet potatoes shows that GM technology is perfectly safe is false.” Since we weren’t around to document the early history of these sweet potatoes, we have no idea if they caused problems. According to Hansen, “We should presume that the first ‘natural’ GM sweet potato, in addition to having some of the Agrobacterium DNA present, also caused a gene to be turned on that produced birth defects, sterility or reduced fertility. As the further breeding occurred, there would be variable levels of this particular toxin among sweet potatoes.”
Hansen stated that folks eating sweet potatoes with high levels of the toxin would have fewer viable offspring, thus natural selection would shift toward decreasing the level of toxin in this vegetable due to the strong selection pressure. Quoting Hansen again: “But far from assuring us that genetic engineering is safe, all that can be concluded from Ars paper is that the scientists have no idea what the history of the development of the sweet potato might be, nor what effects it might have had on human or animal consumers during its evolution.”
Robinson then passed us off to Dr. Jack Heinemann, professor of genetics at the University of Canterbury in New Zealand. He emphasized that modern lab-based GM is a radical departure from “natural” genetic engineering, and that all GM crops and foods must be subjected to safety assessments and testing: “When people move genes into plants, we move constructs that we have pieced together from an average of eight different species simultaneously. In my 25 years of work in HGT, I’ve seen no precedent for this kind of transfer so quickly. When HGT occurs in nature, nature has a chance to react, respond and adjust over many millennia to initially very small descendant populations. When we do it, nature is immediately bombarded by millions of hectares of new organisms in only a few years.”
Quoting Heinemann: “Of course nature can create organisms … by HGT or other means … that are capable of causing us harm. But that is no reason for us to do it unwittingly to ourselves. Nature can squash us with a rock from space, causing injuries indistinguishable from a car crash. This is not a reason to stop motor vehicle safety testing or recommending removing seat belts.”