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Today Was the Worst Day of Paul Broca’s Life

Exactly 150 years ago, an obscure French doctor lit off an unpleasant episode.

Exactly 150 years ago, on March 24, 1863, an obscure French doctor lit the fuse on one of most unpleasant episodes in neuroscience history.

This story actually got started in 1861, when Paul Broca, one of the busts on the Mt. Rushmore of neuroscience, started working at a hospital near Paris. There, Broca met Tan. He was called Tan because that’s pretty much the only word he could say. Ask him his name, his occupation, his fondest dreams in life, and his answers would be, respectively, “Tan,” “tan,” and, of course, “tan.”

Neuroscience was mired in a sticky conflict at the time about brain localization—about whether you could point to a specific spot in the brain as a “memory spot” or “vision spot” or whatever. Since Tan had lost the ability to speak after suffering a stroke, Broca realized that he might reveal the existence of a “language spot.” So when Tan died, Broca performed an autopsy. And although Tan’s brain looked like a mess, Broca did trace his language deficit to a small spot in the frontal lobe. Follow-up work, with other patients who’d lost the ability to speak, confirmed this finding, and what’s now known as Broca’s spot is still recognized as one of the key nodes of language in the brain.

But there was more to learn from those brains. Throughout the last months of 1862 and the first months of 1863, Broca began to realize, albeit fitfully, that all the brains he’d studied had lesions not only in the frontal lobe, but in the left frontal lobe. This implied that the left and right halves of the brain worked differently. Few if any neuroscientists at the time believed such a thing, and Broca struggled with the implications of hemispheric specialization: “I could not easily resign myself to such a subversive consequence,” he later admitted. So although he began broaching the idea in public, he did so coyly, with much hemming and hawing—mentioning all the lefty lesions and then drawing back, inching closer to the idea of specialization, but never articulating it firmly.

Meanwhile, on March 24, 1863, an obscure country physician named Gustave Dax submitted a manuscript to the Académie de Médecine in Paris, in the hopes of getting it published. In an accompanying letter, Dax explained that the manuscript came from his late father, Dr. Marc Dax, who had studied dozens of head injuries in the 1820s and 1830s. Dax père had presented the manuscript at a conference in Montpelier in 1836, and then had been unjustly forgotten by his peers. (Shades of Gregor Mendel there...) And what did this manuscript say? Since many of the men had lost the ability to speak, and since they all had injuries to roughly the same place, Dax concluded that a “language spot” existed in the frontal lobe. Furthermore, since all these lesions appeared in the left brain, the left hemisphere must be the seat of human language. Exactly the idea Broca was playing around with.

The situation got messy in a hurry. For one thing, Broca finally made his first clear public statement on the left hemisphere being the seat of language in early April, just days after the Dax manuscript arrived in Paris. The contents of the manuscript were supposed to be confidential until it was published, but Broca had friends on the committee reviewing it, and almost certainly heard of its conclusions ahead of time. What’s more, it became pretty clear pretty quickly to Dax fils that the committee was going to take its sweet time reviewing the letter—which effectively allowed Broca more time promote “his” discovery.

Dax, however—by all accounts a nasty fellow—didn’t take this lying down, and even accused Broca of purposely omitting references to his poor dear father’s work in his papers. Broca took this charge seriously, going so far as to hunt down other scientists who’d attended the Montpellier conference in 1836, to ask if they remembered Dax presenting the work. None did, and Broca came away not even sure Dax had attended the conference, much less presented a seminal paper there. Indeed, the only evidence that Dax had ever studied language lesions and left-hemisphere specialization so long ago was an old draft of the manuscript that Dax fils had possession of. Suddenly suspicious, Broca had a handwriting analyst study the draft, to see if perhaps the younger Dax had written it. (The analyst ruled he hadn’t, but who knows; the manuscript has since been lost.)

In the end, assigning blame or credit here is awfully tough. There’s no question Broca was the much better scientist. Dax’s work was superficial, almost hasty, and he didn’t even confirm the location of lesions with autopsies; he simply inferred location from where patients said they got hit or felt pain. Nevertheless, Dax got it right—the left brain is the seat of language—and in science, getting it right first often counts for everything. (For all the talk nowadays of how valuable beauty and elegance are in science, elegance still doesn’t beat originality.)

The even tougher debate is how much Broca knew and when he knew it. Pace the younger Dax, historians don’t think that Broca simply ripped Dax père off about left-side language specialization. But did the manuscript somehow influence Broca? Perhaps it was just a coincidence that Broca felt confident enough to come out with his theory right when Dax sent the letter. Or perhaps hearing of the letter and manuscript simply gave Broca confidence that he was on the right track. “Influence” is such a nebulous concept, and unfortunately for historians trying to reconstruct this, Broca doesn’t record any a-ha moment.

Today, textbooks tend to gloss over Dax, and simply award credit to Broca both for finding the language spot and for discovering left-side language specialization. That’s unfortunate, not only because the real story is richer (and juicer) but because it’s much more evocative of the messy way that real science gets done.