Farmers and breeders have for centuries used cross‐breeding to improve the genetic characteristics of crops and animals. Because this process involves gene transfers within the same species, environmental advocates label it “natural” — even though cross‐breeding is clearly man‐made. Modern genetic splicing makes it possible to combine genes from completely different species to produce much‐needed products, including pest‐resistant and high‐yielding crops.
The Bt gene from pest‐resistant bacteria, for example, has been inserted into cotton to create a pest‐resistant Bt cotton. The combination has greatly raised yields and reduced pesticide use. But some activists condemn this as a crime against nature.
When fears about genetically modified foods first arose, little was known about gene flow, also called horizontal gene transfer. The idea that genes could jump across species violated then‐conventional wisdom. But scientific research has established that natural gene transfers regularly occur. So genetic transfers are not a human invention — just a belated human effort to imitate what nature has been doing all along.
This discovery has convinced some longtime campaigners against genetically modified crops to make a U‐turn. British author and journalist Mark Lynas, for example, converted from being an activist opposed to genetically modified food to a firm supporter in a notable 2013 mea culpa speech, in which he apologized for letting his opinions trump the scientific data.
Scientists once thought that gene transfers occurred naturally only in simple organisms like bacteria. But research shows that transfers are also common in complex species, including human beings. Does this genetic intrusion make humans a monster species? Hardly.
The Economist used the headline “Genetically Modified People” for a report on genetic research by Alastair Crisp and Chiara Boschetti, the two Cambridge scientists. They have identified 145 genes that have crossed over from other species to humans.
This is, of course, a tiny fraction of the 20,000 odd genes in a human body. Why then should environmentalists lose sleep over the introduction of a single alien gene into crops?
Research on gene flow is still in its infancy. It could ultimately reveal thousands of alien genes that have entered human DNA. This should be no surprise: Nature has had almost a million years to do its work.
One gene identified by the Cambridge researchers helps hold cells together; it crossed over into humans from a fungus. Marine algae appear to be the source of another human gene associated with fat mass. Bacteria have provided a third gene that helps define blood groups.
Apart from human transfers, the scientists examined gene transfers in nine other primate species, 12 fruit fly species and four nematode worms. They found that the phenomenon was ubiquitous. The researchers considered the possibility that what looked like gene transfers between species might actually be genes both had inherited from a common ancestor millions of years ago.
Genes found in another animal could be a common ancient inheritance. But genes in animals that came from plants or bacteria would almost certainly represent gene flow. Crisp and Boschetti found that, on average, worms had 173 gene transfers, fruit flies 40, and primates had 109. Humans, with 145 transfers, were more genetically modified than other primates.
The researchers found two imported genes for amino‐acid metabolism, 13 for fat metabolism and 15 for modifying large molecules. They identified five immigrant genes that generated valuable anti‐oxidants, and seven that aided the immune system.
Far from creating monsters, the scientists found that genes from alien species appear beneficial. Activists against genetically modified organisms can argue that natural gene transfers have been spaced out over millennia, giving species time to adapt. But every time a natural gene transfer occurred, it carried the same risks as the insertion of a Bt gene into cotton or eggplants.
Besides, all crops, genetically modified or otherwise, are field‐tested for safety before commercial release. The United States has approved dozens of genetically modified crops for commercial use. Virtually all U.S. corn and soybeans today are genetically modified.
Chipotle’s claim of serving food free of genetic modifications is dubious because the meats it serves come from animals and chickens likely fed on genetically modified corn and soybean meal. More important, why should Chipotle even make the claim when its own customers are genetically modified?