Excerpted from Chapter 1, “Genes, Freaks, DNA: How Do Living Things Pass Down Traits to Their Children?” (footnotes and images omitted) from The Violinist’s Thumb: And Other Lost Tales of Love, War, and Genius, as Written by Our Genetic Code by Sam Kean. Reprinted by arrangement with Little, Brown & Company. Copyright © 2012. All rights reserved. No part of this excerpt may be reproduced or printed without permission in writing from the publisher.
Chills and flames, frost and inferno, fire and ice. The two scientists who made the first great discoveries in genetics had a lot in common — not least the fact that both died obscure, mostly unmourned and happily forgotten by many. But whereas one’s legacy perished in fire, the other’s succumbed to ice.
The Violinist's Thumb: And Other Lost Tales of Love, War, and Genius, as Written by Our Genetic Code
(Little, Brown & Company; US: Jul 2012)
The blaze came during the winter of 1884, at a monastery in what’s now the Czech Republic. The friars spent a January day emptying out the office of their deceased abbot, Gregor Mendel, ruthlessly purging his files, consigning everything to a bonfire in the courtyard. Though a warm and capable man, late in life Mendel had become something of an embarrassment to the monastery, the cause for government inquiries, newspaper gossip, even a showdown with a local sheriff. (Mendel won.) No relatives came by to pick up Mendel’s things, and the monks burned his papers for the same reason you’d cauterize a wound — to sterilize, and stanch embarrassment. No record survives of what they looked like, but among those documents were sheaves of papers, or perhaps a lab notebook with a plain cover, probably coated in dust from disuse. The yellowed pages would have been full of sketches of pea plants and tables of numbers (Mendel adored numbers), and they probably didn’t kick up any more smoke and ash than other papers when incinerated. But the burning of those papers — burned on the exact spot where Mendel had kept his greenhouse years before — destroyed the only original record of the discovery of the gene.
The chills came during that same winter of 1884 — as they had for many winters before, and would for too few winters after. Johannes Friedrich Miescher, a middling professor of physiology in Switzerland, was studying salmon, and among his other projects he was indulging a long-standing obsession with a substance — a cottony gray paste — he’d extracted from salmon sperm years before. To keep the delicate sperm from perishing in the open air, Miescher had to throw the windows open to the cold and refrigerate his lab the old-fashioned way, exposing himself day in and day out to the Swiss winter. Getting any work done required superhuman focus, and that was the one asset even people who thought little of Miescher would admit he had. (Earlier in his career, friends had to drag him from his lab bench one afternoon to attend his wedding; the ceremony had slipped his mind.) Despite being so driven, Miescher had pathetically little to show for it — his lifetime scientific output was meager. Still, he kept the windows open and kept shivering year after year, though he knew it was slowly killing him. And he still never got to the bottom of that milky gray substance, DNA.
DNA and genes, genes and DNA. Nowadays the words have become synonymous. The mind rushes to link them, like Gilbert and Sullivan or Watson and Crick. So it seems fitting that
Miescher and Mendel discovered DNA and genes almost simultaneously in the 1860s, two monastic men just four hundred miles apart in the German-speaking span of middle Europe. It seems more than fitting; it seems fated.
But to understand what DNA and genes really are, we have to decouple the two words. They’re not identical and never have been. DNA is a thing — a chemical that sticks to your fingers. Genes have a physical nature, too; in fact, they’re made of long stretches of DNA. But in some ways genes are better viewed as conceptual, not material. A gene is really information — more like a story, with DNA as the language the story is written in. DNA and genes combine to form larger structures called chromosomes, DNA-rich volumes that house most of the genes in living things. Chromosomes in turn reside in the cell nucleus, a library with instructions that run our entire bodies.
All these structures play important roles in genetics and heredity, but despite the near-simultaneous discovery of each in the 1800s, no one connected DNA and genes for almost a century, and both discoverers died uncelebrated. How biologists finally yoked genes and DNA together is the first epic story in the science of inheritance, and even today, efforts to refine the relationship between genes and DNA drive genetics forward.
Mendel and Miescher began their work at a time when folk theories — some uproarious or bizarre, some quite ingenious, in their way — dominated most people’s thinking about heredity, and for centuries these folk theories had colored their views about why we inherit different traits.
Everyone knew on some level of course that children resemble parents. Red hair, baldness, lunacy, receding chins, even extra thumbs, could all be traced up and down a genealogical tree. And fairy tales — those codifiers of the collective unconscious — often turned on some wretch being a “true” prince(ss) with a royal bloodline, a biological core that neither rags nor an amphibian frame could sully.
That’s mostly common sense. But the mechanism of heredity — how exactly traits got passed from generation to generation — baffled even the most intelligent thinkers, and the vagaries of this process led to many of the wilder theories that circulated before and even during the 1800s. One ubiquitous folk theory, “maternal impressions,” held that if a pregnant woman saw something ghoulish or suffered intense emotions, the experience would scar her child. One woman who never satisfied an intense prenatal craving for strawberries gave birth to a baby covered with red, strawberry-shaped splotches. The same could happen with bacon. Another woman bashed her head on a sack of coal, and her child had half, but only half, a head of black hair. More direly, doctors in the 1600s reported that a woman in Naples, after being startled by sea monsters, bore a son covered in scales, who ate fish exclusively and gave off fishy odors. Bishops told cautionary tales of a woman who seduced her actor husband backstage in full costume. He was playing Mephistopheles; they had a child with hooves and horns. A beggar with one arm spooked a woman into having a one-armed child. Pregnant women who pulled off crowded streets to pee in churchyards invariably produced bed wetters. Carrying fireplace logs about in your apron, next to the bulging tummy, would produce a grotesquely well-hung lad. About the only recorded happy case of maternal impressions involved a patriotic woman in Paris in the 1790s whose son had a birthmark on his chest shaped like a Phrygian cap— those elfish hats with a flop of material on top. Phrygian caps were symbols of freedom to the new French republic, and the delighted government awarded her a lifetime pension.
Much of this folklore intersected with religious belief, and people naturally interpreted serious birth defects — cyclopean eyes, external hearts, full coats of body hair — as back‑of‑the-Bible warnings about sin, wrath, and divine justice. One example from the 1680s involved a cruel bailiff in Scotland named Bell, who arrested two female religious dissenters, lashed them to poles near the shore, and let the tide swallow them. Bell added insult by taunting the women, then drowned the younger, more stubborn one with his own hands. Later, when asked about the murders, Bell always laughed, joking that the women must be having a high time now, scuttling around among the crabs. The joke was on Bell: after he married, his children were born with a severe defect that twisted their forearms into two awful pincers. These crab claws proved highly heritable to their children and grandchildren, too. It didn’t take a biblical scholar to see that the iniquity of the father had been visited upon the children, unto the third and fourth generations. (And beyond: cases popped up in Scotland as late as 1900.)
If maternal impressions stressed environmental influences, other theories of inheritance had strong congenital flavors. One, preformationism, grew out of the medieval alchemists’ quest to create a homunculus, a miniature, even microscopic, human being. Homunculi were the biological philosopher’s stone, and creating one showed that an alchemist possessed the power of gods. (The process of creation was somewhat less dignified. One recipe called for fermenting sperm, horse dung, and urine in a pumpkin for six weeks.) By the late 1600s, some protoscientists had stolen the idea of the homunculus and were arguing that one must live inside each female egg cell. This neatly did away with the question of how living embryos arose from seemingly dead blobs of matter. Under preformationist theory, such spontaneous generation wasn’t necessary: homuncular babies were indeed preformed and merely needed a trigger, like sperm, to grow. This idea had only one problem: as critics pointed out, it introduced an infinite regress, since a woman necessarily had to have children, as well as their children, and their children, stuffed inside her, like Russian matryoshka nesting dolls. Indeed, adherents of “ovism” could only deduce that God had crammed the entire human race into Eve’s ovaries on day one. (Or rather, day six of Genesis.) “Spermists” had it even worse — Adam must have had humanity entire sardined into his even tinier sperms. Yet after the first microscopes appeared, a few spermists tricked themselves into seeing tiny humans bobbing around in puddles of semen. Both ovism and spermism gained credence in part because they explained original sin: we all resided inside Adam or Eve during their banishment from Eden and therefore all share the taint. But spermism also introduced theological quandaries — for what happened to the endless number of unbaptized souls that perished every time a man ejaculated?
However poetic or deliciously bawdy these theories were, biologists in Miescher’s day scoffed at them as old wives’ tales. These men wanted to banish wild anecdotes and vague “life forces” from science and ground all heredity and development in chemistry instead.