The Violinist's Thumb: And Other Lost Tales of Love, War, and Genius, as Written by Our Genetic Code by Sam Kean Read Free Book Online

various ways. The results were complex, but one result especially excited Morgan: after crossing some red-eyed descendants with each other, he discovered among the offspring a 3:1 ratio of red to white eyes.
    The year before, in 1909, Morgan had heard the Danish botanist Wilhelm Johannsen lecture about Mendelian ratios at Columbia. Johannsen used the occasion to promote his newly minted word,
gene,
a proposed unit of inheritance. Johannsen and others freely admitted that genes were convenient fictions, linguistic placeholders for, well, something. But they insisted that their ignorance about the biochemical details of genes shouldn’t invalidate the usefulness of the gene concept for studying inheritance (similar to how psychologists today can study euphoria or depression without understanding the brain in detail). Morgan found the lecture too speculative, but his experimental results—3:1—promptly lowered his prejudice to Mendel.
    This was quite a volte-face for Morgan, but it was just the start. The eye-color ratios convinced him that gene theory wasn’t bunk. But where were genes actually located? Perhaps on chromosomes, but fruit flies had hundreds of inheritable traits and only four chromosomes. Assuming one trait per chromosome, as many scientists did, there weren’t enough to go around. Morgan didn’t want to get dragged into debates on so-calledchromosome theory, but a subsequent discovery left him no choice: because when he scrutinized his white-eyed flies, he discovered that every last mutant was male. Scientists already knew that one chromosome determined the gender of flies. (As in mammals, female flies have two X chromosomes, males one.) Now the white-eye gene was linked to that chromosome as well—putting two traits on it. Soon the fly boys found other genes—stubby wings, yellow bodies—also linked exclusively to males. The conclusion was inescapable: they’d proved that multiple genes rode around together on one chromosome. * That Morgan had proved this practically against his own will mattered little; he began to champion chromosome theory anyway.
    Overthrowing old beliefs like this became a habit with Morgan, simultaneously his most admirable and most maddening trait. Although he encouraged theoretical discussions in the fly room, Morgan considered new theories cheap and facile—worth little until cross-examined in the lab. He didn’t seem to grasp that scientists need theories as guides, to decide what’s relevant and what’s not, to frame their results and prevent muddled thinking. Even undergraduates like Bridges and Sturtevant—and especially a student who joined the fly room later, the abrasively brilliant and brilliantly abrasive Hermann Muller—grew hair-rippingly frustrated with Morgan in the many quarrels they had over genes and heredity. And then, just as exasperating, when someone did wrestle Morgan into a headlock and convince him he was wrong, Morgan would ditch his old ideas and with no embarrassment whatsoever absorb the new ones as obvious.
    To Morgan, this quasi plagiarism was no big deal. Everyone was working toward the same goal (
right,
fellas?), and only experiments mattered anyway. And to his credit, his about-faces proved that Morgan listened to his assistants, a contrast to the condescending relationship most European scientists had with their help. For this reason Bridges and Sturtevant alwayspublicly professed their loyalty to Morgan. But visitors sometimes picked up on sibling rivalries among the assistants, and secret smoldering. Morgan didn’t mean to connive or manipulate; credit for ideas just meant that little to him.
    Nevertheless ideas kept ambushing Morgan, ideas he hated. Because not long after the unified gene-chromosome theory emerged, it nearly unraveled, and only a radical idea could salvage it. Again, Morgan had determined that multiple genes clustered together on one chromosome. And he knew from other scientists’ work that parents pass whole