Two hundred years ago Englishmen used to rave about the beautiful complexions of milk maids who seemed immune from the dread scourge of smallpox, which disfigured the people it did not kill. It was Edward Jenner who figured out that milk maids were exposed to cowpox, a lesser disease, and that cowpox immunized them from smallpox.
He developed a cowpox vaccine that has been so successful that today the only smallpox bacilli left on earth are isolated in laboratories in the United States and Russia.
Many people thought, however, that vaccinations were against nature and dangerous. Illustrated predictions of milk maids with cows growing out of their bodies appeared in the press.
Today a similar wave of fearful but equally unscientific protest is rising over the genetic altering of crops. Many Europeans have said they will not accept genetically altered food.
The focus has moved to Boston this weekend with the BIO2000 International Meeting and Exhibition, which opens here today - a showcase for the nascent industry.
Biotechnology is so new that, as Henri Termeer, CEO of Genzyme, put it: If it were the Boston Marathon we would be just lacing up our sneakers.
And this is what many critics have against it. They say the industry is moving too fast, is too commercially driven, that we do not know the end results of genetic engineering.
They say that the brakes ought to be applied with heavy regulation, and some would put a stop to the entire enterprise. Protesters compare themselves to Rachel Carson, whose landmark book, "Silent Spring," blew the whistle on DDT-based pesticides and probably saved many species from extinction.
But unlike Carson, the biologically altered food opponents have little evidence to back up their fears. The idea of mixing fish genes with tomato genes may make the stomach queasy, but a gene is a gene - neither a fish nor a tomato - and all human beings share genes with animals and plants. The image of fish heads growing out of tomatoes misunderstands the process as much as cows growing out of a milk maid did in the 18th century.
The protesters also seem not to appreciate the careful testing to which genetically altered crops are subjected by the Environmental Protection Agency, the Food and Drug Administration, and the Department of Agriculture.
Mankind has been altering crops since people learned to breed wild grasses into edible food. And animal husbandry has altered the wild beasts into the farm animals we see today.
Yes, we need to proceed carefully with proper regulation, and yes, bio-engineering is different from the cross-breeding of the past. And although the danger to Monarch butterflies, for example, has been exaggerated, the industry needs to guard against unintended consequences.
But to stop the genetic altering of food that can make crops insect-resistant, for example, or stronger and more able to survive, would be to deprive mankind of a benefit that may become necessary to save the world in the centuries to come when populations increase.
Much of the protest in Boston this weekend is based on the same kind of ignorance that tried to end Edward Jenners immunizations two centuries ago.