Chapter 1: The Meridian

The cohort data from Laishan arrived on a Tuesday. Maren was eating an apple and had to put it down to make room on her desk. Her teeth marks were already browning on the skin by the time the files finished loading. It was the third-generation set. She'd been waiting for it since winter.

The analysis lab at six in the morning smelled like floor polish and the limestone the building was cut from. Maren's tea was still too hot to drink. She held the cup against her sternum and let the heat soak through her shirt while the numbers populated. Methylation patterns across four hundred and twelve individuals, aged six to eleven, born to parents born to parents who had never performed sustained physical labor of any kind. Three generations of automation. Three generations of data. She liked looking at numbers before anyone told her what to think about them. They were just themselves.

Maren had been a biostatistician at the Meridian Institute for nine years. She was thirty-four. She could describe what she did as "I look at the numbers before anyone argues about them." The Institute existed to study the biological effects of sedentary living across generations, and the people who worked there had strong opinions about what the data meant.

The Karst plateau in September was still warm enough to leave windows open. The analysis lab was on the second floor of the main building, and from her workstation she could hear the oak grove that bordered the eastern courtyard. Cicadas, mostly. Wind through leaves that were just beginning to think about turning. The campus had been built into the landscape rather than on top of it, which was either good architecture or stubbornness; the hallways followed the contour of the limestone, and there was a particular staircase near the west annex that nobody used because it was steep enough to qualify as exercise. Tomas used it daily.

She pulled up the methylation profiles. Gross metrics first — the broad strokes, the things a clinician would check. Her fingers moved through the protocol on muscle memory: mean methylation age versus chronological age, variance, deviation from the reference population. Then the tissue-specific panels. Then the expression markers. BDNF regulation. Myokine pathway activation. Inflammatory baseline. Metabolic gene accessibility. The tea cooled in her hands as the numbers came up.

The gross metrics were fine. They were always fine. The Laishan children were healthy by every standard clinical measure. Growth curves normal. Cognitive benchmarks normal. If you ran them through a standard pediatric assessment, you would find nothing wrong.

Maren did not run them through a standard pediatric assessment. She ran them through the Institute's protocol, which looked at the layers underneath the layers, and this is where things got interesting. Or troubling. Or both.

The BDNF regulatory markers were lower than the second-generation cohort. Not dramatically. Not clinically significant, if you were a clinician. But the trend was there, and it was in the same direction it had been moving since the first-generation data: down. A slow, generational dimming of the pathway that regulated neuroplasticity. The children's brains were fine today. The question was whether their children's brains would be fine, and their grandchildren's, and where the curve flattened or whether it flattened at all.

She made a note. She ate her apple.

The garlic hit her in the stairwell, two floors down. By the time she reached the apartment door she could hear the knife on the cutting board — a fast, even rhythm that meant Tomas had had a good day in the expression lab. He cooked when his work went well. When it didn't, they ate at the refectory with everyone else, which was perfectly fine food, but Tomas liked to cook and he was better at it than the refectory staff, and he knew it, and Maren found this vanity endearing.

She dropped her bag on the chair that existed for that purpose. The kitchen was warm from the stove and smelled like rosemary and olive oil and the particular sweetness of garlic just starting to brown.

"The Laishan data came in," she said.

"Third gen?" He didn't look up. The knife kept its rhythm. Through the window behind him, the limestone shelves on the western slope caught the evening light.

"Third gen."

"And?"

Maren took a glass from the shelf. "The gross metrics are clean."

"But."

"I didn't say but."

"You have a but face."

She poured water from the filtered jug. "The BDNF trend is continuing. Down again. Same slope as gen one to gen two." She drank. "It's not a crisis. It's just a line going in one direction for three data points."

"Three generational data points."

"Which is not a lot of data points."

"It's the only kind of data point that matters for this question."

Tomas did expression therapy — methylation correction, epigenetic reprogramming. She counted the decline; he designed the fixes.

"Petrič wants to do a full presentation on the Laishan set for the Friday seminar," Tomas said, turning back to the stove.

"Of course she does."

"She's going to use it as ammunition."

"Davorka doesn't use ammunition. She uses data."

"She uses data as ammunition. There's a distinction, but it's subtle."

Maren smiled. This was not entirely unfair. Davorka Petrič had trained her, hired her, and had been at the Institute since before Maren was born. She had opinions.

The Friday seminar was held in the main lecture hall, which seated about a hundred and twenty people and usually held about ninety, because the Institute's permanent staff was ninety-three and the visiting researchers fluctuated between five and fifteen and not everyone came to every seminar, although most people came to Davorka's because she was a good speaker and also because arguing with her was a form of entertainment that the plateau's limited social calendar could not easily replace.

Maren sat in the fourth row, where she always sat. Josip Brlan had saved her the seat next to him, as he had every Friday since she'd helped him debug a statistical model three years ago. He was already there, knees wide, thermos balanced on one thigh, smelling faintly of the microbiome lab's ethanol wash. He organized his loyalties early and maintained them with a stubbornness that was either admirable or exhausting depending on how much of it was aimed at you.

Davorka stood at the front, rolling up the sleeves of today's linen shirt — the green one; she had five, rotated daily — revealing ropy forearms. She uncapped a marker. She did not believe in slides.

"The Laishan third-generation data is in," she began. "Maren has processed the initial metrics and I've reviewed her work. I want to talk about what the BDNF regulatory trend means and what it doesn't mean, because half of you will overreact in one direction and the other half will overreact in the other direction, and I'd like to save us all the time."

A laugh from the room. Maren could feel the divide without looking — who leaned forward when Davorka spoke, who sat back and waited for the rebuttal.

Maren had noticed she agreed with different camps on different days. She'd mentioned this to Davorka once. Davorka had said, "Good. That means you're still looking at the data instead of your own reflection."

Davorka walked through the BDNF findings without hurrying. She put the numbers on the board with a marker.

"Three generations," Davorka said, drawing the line. "The slope is consistent. It is not steep. Nobody's children are going to wake up tomorrow unable to form new memories. But the pathway is dimming, and the dimming is heritable, and we are now three data points into a trend that shows no sign of leveling off. The question is not whether this is happening. The question is what you propose to do about it."

She looked at the room. Her eyes found Yael Kassar in the second row.

"Yael, I believe you have thoughts."

Kassar stood. She was younger than Davorka by fifteen years, precise in her speech, and genuinely brilliant in ways that Maren found intimidating. "We have a CRISPR-Cas12 variant in trial that targets the BDNF promoter methylation directly. The second-generation expression correction in animal models is running at eighty-seven percent. We're proposing human trials for next year."

"You're proposing to edit the methylation."

"We're proposing to restore it. There's a difference."

"Is there?" Davorka put the marker down. "You're intervening in an epigenetic pathway that's expressing a particular way in response to environmental conditions. You're proposing to change the expression without changing the conditions. I'd call that editing."

"I'd call it medicine."

The room was quiet the way it got quiet when Davorka and Kassar talked directly to each other. Not tense, exactly. Attentive. The way you watch two people play a game you know both of them are good at.

"The pathway is dimming because the bodies aren't being used," Davorka said. "You want to repaint the gauge. I want to fix the engine."

"Your engine fix requires restructuring the entire built environment around mandatory physical labor. My gauge fix requires a single-course therapy a child can receive at age two."

Davorka picked the marker back up. She turned it end over end between her fingers, once, twice. "And when it doesn't catch the other eleven thousand things that physical exertion does? The myokine cascades. The inflammatory regulation. The bone density maintenance." She was counting on her fingers now, which was a thing she did when she wanted you to feel the weight of a list. "The microbiome signaling. The circadian entrainment. The social bonding from communal effort." She stopped. "You'll develop eleven thousand more therapies?"

"Perhaps."

"That's not science. That's hubris wearing a lab coat."

Kassar crossed her legs. She had heard this before. "And restructuring civilization around crank handles and flywheels is what, exactly?"

"An admission that the system is more complex than our ability to model it."

Maren watched. She had heard this argument dozens of times. The words changed. The shape didn't.

Josip leaned toward her. "Petrič is in good form today," he whispered.

"She's always in good form."

"Kassar's not wrong, though. About the animal models."

"I know."

"You have a face."

"Everyone keeps telling me about my face."

The campus at night was quiet in a way that cities were not. The Karst plateau sat high enough that you could see the lights of the lowland towns to the south, but the Institute itself kept its lighting minimal; something about the founding charter and respecting circadian rhythms, which was the kind of principle that sounded idealistic until you lived there and realized that sleeping well in real darkness was the sort of luxury you didn't want to give back.

Maren and Tomas walked the long way home, through the oak grove and past the weather station that no one had maintained since Dr. Horta retired. The instruments were still there, measuring things and sending the measurements to a database that nobody checked.

"Davorka was hard on Kassar today," Tomas said.

"Kassar held her own."

"She always does. That's not the point." He walked with his hands in his pockets, which he did when he was thinking about something he hadn't finished thinking about. "The eighty-seven percent figure is real, Maren. The animal models are solid. We're not guessing anymore."

"You're not guessing about BDNF promoter methylation. That's one pathway."

"It's the pathway everyone's been watching."

"It's the pathway everyone's been measuring. Those aren't the same thing."

He looked at her. She'd said something he couldn't easily dismiss.

"Let's not do this tonight," he said.

"I'm not doing anything. You brought up the eighty-seven percent."

"I brought up the eighty-seven percent because I'm proud of my work and I wanted my partner to acknowledge it."

She reached over and took his hand. "I acknowledge it. Eighty-seven percent is remarkable. I mean that."

He laced his fingers through hers. She could feel his pulse in his thumb.

"I'm proud of you too," she said. "For what it's worth."

"It's worth a lot."

They walked. The gravel path crunched under their feet and the air had cooled enough that she could feel the transition on her forearms where her sleeves ended. Somewhere in the oak grove an owl was working through its evening repertoire — four notes, repeated with a regularity that Maren suspected Josip could have mapped to a statistical distribution if anyone had asked him to. Nobody had. This was, she thought, also fine.

In their apartment, Tomas fell asleep before she did, which was normal. His breathing was even, face slack. Maren lay beside him and listened to his breathing. The sheets smelled like laundry soap and, faintly, the rosemary from dinner. His shoulder was warm against hers. She was not thinking about the Laishan data, exactly. She was thinking about the feeling that came with it — a low hum of something not yet resolved, something she couldn't name, sitting in her chest like a question her body was asking that her mind hadn't caught up to yet.

She got up, quietly, and went to the kitchen. She poured water and stood by the window. The hillside was dark except for the limestone shelves, which caught enough starlight to be visible.

She finished her water and went back to bed.