Although this is theoretical, geneticists are enthusiastic about this approach to the prevention of disease, and its possible application to the elimination of cancer cells. As is almost always the case with important discoveries and novel technologies, there are many that warn against the potential dangers of genetic engineering. Many of the warnings come from people who are untrained in genetics, but occasionally, the warnings come from scientists. Others pointed out that humans fed only potatoes for ten years might not fare well either. In another, more compelling case, John Losey and colleagues at Cornell University in Ithaca reported that the larvae of monarch butterflies ate less, grew slowly and often died when fed milkweed leaves dusted with genetically engineered pollen from corn.
Milkweed is the exclusive diet of monarch larvae.
And nearly half of the larvae exposed to milkweed dusted with the genetically engineered pollen, died after four days. Others argued that harmful concentrations of pollen were not likely to be found more than a few feet from the flowering corn and that harmful concentrations of the pollen on milkweed would quickly be eliminated by rain and wind. It was also noted that corn pollinates only once each year whereas monarchs breed year round. But the use of genetically engineered crops remains highly controversial. It is not difficult to envision a time when early human embryos might be tested for genetic diseases, and then treated accordingly.