The Fly Who Saved A Million Lives (Or More)

It’s a funny thing about history: lots of folks jabber away telling the rest of us that we don’t know our history, and that failure leads to a lot of getting bitten in the gluteus maximus. Philosopher George Santayana expressed this concern most eloquently and famously thus: “Those who fail to learn from history are doomed to repeat it.” There are enough examples of Santayana’s warning coming true in just the last century to write several volumes. In a similar vein we are also told that history is written by the winners, to which I now add that it is written by those who can write. You see, I truly believe that the most influential being of the twentieth century was not Albert Einstein, nor Winston Churchill, Franklin Roosevelt, or William Paley (founder of CBS). In fact, the most influential being couldn’t read or write, and wasn’t even a human being; he was a fly. This is his story.

You’ve probably heard of Gregor Mendel, the Austrian monk who, in the 1860s, was the first person to figure out the basic principles of inheritance. While the United States was waging its Civil War, the curious monk was trying to understand the scientific principles that would help the local farmers grow better crops and livestock. Mendel had wanted to do his experiments by breeding locally collected mice, but as a resident of a Catholic monastery he quickly found that the other brothers were intensely opposed to any sexual activity taking place under that roof. Fortunately, the boss (or, if you prefer, abbot) convinced Mendel that the basic rules governing inheritance should be the same in plants as in animals. Mendel agreed, and he began his extensive breeding experiments with pea plants. By the time he finished his studies Mendel had raised, counted, and measured a lot of peas, and he was able to calculate the foundation principles of how genetics work. Here is what he came up with:

First: genes are the substances that guide the development of a body, and they are clustered together on chromosomes.

Second: each parent contributes one complete set of its genes to each offspring, so, for example, you got half your eye-color genes from Mom and half from Dad.

Third: the sex of an individual is determined by their chromosomes – but he didn’t understand how that worked

Fourth: for each trait, such as pea color or plant height, a gene may occur as either a dominant form or a recessive form; if even one dominant version is present, it is expressed and the recessive trait is not.

Now skip ahead to 1900, three decades after Mendel passed on to that great pea patch in the sky. A Dutch botanist named Hugo de Vries had discovered Mendel’s publications and picked up the study of genetic principles. In particular, de Vries wanted to understand how new variations developed. For example, he knew that some flowers could occur as red or white forms, so how did red or purple varieties arise? This clever fellow figured that to get a new trait you had to change an old gene – instead of having only types A and B, one of them somehow is altered to become C. That new version was not present in either parent or grandparent, it is entirely new. Scholar that he was, de Vries knew that Latin word meaning “to change” is mutare, so he called those new genes “mutants.”

Alas, de Vries had several examples of plant mutations that later examination turned out to be something else. In a great irony in science, de Vries came up with a good definition for a real event that he did not have available as an example!

You’re wondering about the fly, aren’t you? Hang on, I’m getting there.

Columbia University of 1910 was already a formidable and prestigious school, and pronouncements from its faculty carried considerable weight. The school hired a volatile young professor to run their foundling genetics program, and chose one with a solid reputation and well-known doubt about the reality of earlier genetics research. His intent was to expose Mendel, de Vries, and others as poor scientists whose work was based more on hope and fudged data than real research. After all, he thought, no one had actually seen a gene, or had anything but a mathematical model for how sex was determined. Most important, he felt that genes were a myth, and if he could prove it he would summarily destroy the theories of Darwin, Mendel, and de Vries. His name was Thomas Hunt Morgan and he was to be thwarted in all of his efforts. In so doing, he would become the father of modern genetics, paving the way for the discovery of the functions and structure of DNA, genetic screening, molecular biology, and a considerable number of modern medical innovations.

But before he could claim that illustrious mantle he needed some help. Here is where that fly comes in. When Morgan took the position at Columbia, he was not given a lot of room in which to work; after all, very few folks thought that genes were real or that genetics was science. Given his small space, Morgan had to come up with a test creature that could be produced rapidly, reliably, and in the confines of an area the size of a large closet. That’s how he chose fruit flies, which everyone who ever stayed awake through high school biology classes learned are the most important organisms ever used in learning about genetics. Morgan started it all in what became known as the Columbia Fly Room.

For two years Morgan and his two graduate students bred and examined fruit flies. Generation after generation produced thousands of flies that looked pretty much like their parents: two wings, red eyes, cinnamon-colored body. Put them under a magnifying glass and you could see the differences between the males and females. The team kept breeding and examining flies, learning, undoubtedly, more about fruit flies than even another fruit fly would want to know. What they wanted to find was a case of mutation, the kind de Vries defined but never found. After two solid years of studying tens of thousands of flies, Morgan told a visiting colleague that he felt he had wasted all that time. Breeding flies produced no evidence that supported Mendel’s theory or his own counter-theory. He was getting close to the point where he could fold up the project and claim, truthfully, that two years of intense research had yielded no evidence at all to support genetic theory.

Now for the hero of this story. One day in 1910 Morgan’s team found something odd in one of the little bottles that contained a colony of flies and the banana mash they feed upon. Looking up from the specimen platform under the microscope, anesthetized so he wouldn’t fly away, was a male fruit fly with white eyes. No fly had ever been seen with anything but red eyes, including the parents, grandparents, and great-great grandparents back to the founding flies of 1908. Morgan had to wonder if this was just some kind of odd defect or a true mutation. There was only one way to tell.

Morgan needed that fly to mate, for only if the trait showed up in his descendants would the mutation theory be confirmed. Unfortunately, that fly was sickly and weak, and seemed to be on the verge of death. Luckily for science, he gathered enough strength to mate with one female fly, after which he died. His mate was quickly sequestered in a bottle of her own, and she soon produced eggs that resulted in 1,237 offspring. Another thing you should remember if you got through that biology class is that Mendel predicted that the sons and daughters should all express only one version of a specific gene if it comes in dominant and recessive forms. A recessive trait only shows up again in the grandchildren’s generation.

So, the Fly Room team allowed all those brothers and sisters to mate, and they awaited their eggs to hatch. Here’s where it gets exciting; of the offspring, 3,470 had red eyes and 782 had white eyes! On top of that, every single white-eyed fly was a male. The ratio of white-eyed to red-eyed flies was almost exactly what Mendel’s formula predicted. Ergo, the stuff that produced white eyes – a gene – was real, and it was also a real mutation. Whatever else Morgan may have been, he was an honest and competent scientist, and he quickly switched his position on Mendel, de Vries, and genetics. Because of that one white-eyed male fly, Morgan and his team salvaged genetics from the role of scientific heresy to highly respected research subject. As a direct result of that fly, Morgan and his students were able to quickly go on to prove that genes are real, mutations are real, sex is determined by chromosomes, and some genes are sex-linked (determined by the sex of the individual). Also, his experiments went on to validate everything Mendel had proposed, which is why we consider Mendel, and not Morgan, the founder of the science of genetics. Once the most basic of foundations had been established by no less an academic powerhouse as Columbia University, the field of genetics became respectable and took off like a fruit fly out of a banana bottle. Because of that one fly, Watson and Crick would be able to figure out the structure of DNA, the development of antibiotics could take place, and billions of dollars worth of research, medical and agricultural advances, and all the jobs associated with them, would take place. Because of that fly, biology students everywhere had to learn about Mendel, statistics, and fruit flies. Millions of lives have been saved as a result, and the theories of scientific luminaries including Darwin, Mendel, and de Vries have been thoroughly vindicated.

Because of that one white-eyed male fruit fly. What other being made so many major innovations and advances possible?

Dr. Robert Sprackland is a featured writer for Xomba.com. Read the rest of his work here .