Discovery isn’t always pretty, inspiring, or even mildly interesting. Sometimes it’s literally the tale of watching flies fuck.
Today’s Moment of Science… the Fly Room.
The mystery of how traits are passed on from one generation to the next eluded scientists for far longer than it needed to. Blending inheritance was a commonly accepted explanation in the nineteenth century, suggesting that our traits are an average of sorts from both parents. Which, to be fair, was a smidge closer to reality than saltationism, Lamarckism, and Lysenkoism.
In the 1850s-1860s, Gregor Mendel’s breeding experiments with 30,000 some odd pea plants produced the first thing we’d recognize today as genetics. He worked out the concepts of dominant and recessive traits. He observed that genes for various traits assort independently of each other. However, when he published his findings, his breakthrough was largely unnoticed, misunderstood, or the subject of mockery.
“My time will come,” he was quoted as telling a friend.
In the 1890s, after Mendel’s death, biologists Carl Correns in Germany and Hugo De Vries in the Netherlands independently stumbled across his work. They both published papers in 1900 that gave Mendel some long-overdue credit.
So, drosophila, the humble fruit fly.
To study genetics decades before the advent of the PCR, your best option was to breed, interbreed, and crossbreed organisms. Lots of them, and fast. If you were lucky, you’d eventually see something worth writing about. The more generations of offspring available to breed and observe, the better.
It’s not that biologists had some deep love for fruit flies to speak of. It’s that these itsy organisms had a ten day gap between generations, females could bang out up to a hundred eggs a day, and they were super easy to study after you got them high as fuck on ether.
In 1908, Thomas Hunt Morgan began studying fruit flies in a small room at Columbia University. Morgan wasn’t convinced about Mendelian genetics at first, and primarily set out to investigate mutationism. An older pet theory of De Vries that’s similar to saltationism, it proposed that speciation could occur “instantaneously (via) large-scale genetic changes.” Only the slightest of exaggerations, but it’s a bit like thinking a pigeon could ‘whoops’ out a flamingo.
Morgan and his team wanted to see what fruit flies could ‘whoops’ out.
For the first two years, they just shat out more boring old fruit flies that spent their lives making babies and getting high on ether. Morgan said “there’s two years of work, wasted.” But that wasn’t long before they got their first apparent mutant: a white eyed male born in a litter of red eyed drosophila.
Morgan did the only sensible thing: watched more flies fuck.
That first generation of offspring, perhaps disappointingly at the time, didn’t have any white eyed offspring. They also didn’t have pink eyes, which wasn’t a good sign for the hypothesis of ‘blending inheritance.’ The next generation though? Males had inherited the white-eyed trait at a ratio of three red eyed flies to one with white eyes. Which- I’m sure coincidentally- is exactly the rate at which Mendelian genetics predicts recessive genes will make themselves apparent.
A joint effort including geneticists Alfred Sturtevant, Hermann Muller and Calvin Bridges, the lab started finding and crossbreeding more mutants. Sturtevant made one of the earliest maps of genes on a fruit fly chromosome. Muller found that there was a direct relationship between exposure to x-rays and mutations, stumbling on the discovery for x-ray mutagenesis. Bridges did groundbreaking work into sex-linked traits. He’s also credited along with Morgan for the discovery of nondisjunction, which is when chromosomes split up and have a super messy division of assets.
This is a long way of saying they tortured the foundations of genetics out of those goddamn flies. When reached for comment, the flies responded “don’t care, had sex.”
Their groundbreaking joint publication was The Mechanism of Mendelian Heredity. Vindicating Mendel, it all but cemented the acceptance of Mendelian genetics and the chromosome theory of inheritance in biology.
This has been your Moment of Science, still picturing a very confused pigeon with a baby flamingo.
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Part of my work-study program at UNC Chapel Hill in 1974 was in the genetics lab sorting fruit flies by sex and eye type. We gave the little fuckers a roofie of ether, sorted under a microscope with artist brushes, then the keepers were put in a fresh beaker of sugary baby shit brown stuff. The defective and undesirable little bastards were dumped while unconscious in a jar of oil. As hundreds of little stoned flies sank into their oily death, a cloud of tiny bubbles would rise as they expelled their last breath.