The Same Book, Different Pages

The brine shrimp eggs looked like brown dust on the surface of the saltwater. Soren had measured the salt twice. Maya had not measured anything. She was holding the jar up to the porch light, turning it.

"They're all the same," she said.

"That's the point," said Soren. "Dried out. They wake up when they hit salt water."

"No. I mean they're identical. Every single one. Same speck. And tomorrow they'll be a swimming thing with eyes and a tail and a gut." She set the jar down hard enough that the dust swirled. "Where does the eye come from?"

Soren wrote the word eye in his notebook, then stopped, because he didn't have anything to put after it.

"From the egg," he said.

"But the egg is one thing. The eye and the gut are different things. How does one thing know to become two different things?"

Soren looked at the speck of dust through the glass. He had hatched these before. He had never once asked that question, and now that Maya had said it out loud he could not believe he had missed it.

"Okay," he said slowly. "Every cell has the same DNA. Whole body. Same in your eye, same in your gut, same in your toe."

"That's wrong," said Maya.

"It's not wrong. It's true. I read it."

"Then it can't be true." Maya started pacing on the cold grass. "If the eye cells and the gut cells have the exact same instructions, they'd be the exact same thing. You can't build two different things from one set of instructions. That's like baking the same recipe and getting a cake one time and a bicycle the other time."

Soren opened his mouth to argue and found she was right, which was the problem. Two things he believed were both true. They couldn't both be true.

He went inside and came back with a cookbook from the kitchen, his mother watching him over her coffee, asking nothing, used to this. He sat down on the step and put the book between them.

"Same book," he said. "Every cell gets the whole book."

"Right. So same cells."

"No, wait." He flipped it open. "It's a recipe book. Hundreds of recipes. The eye cell reads the eye pages. The gut cell reads the gut pages. Same book. Different pages open."

Maya stopped pacing.

"They turn pages off," she said.

"Genes," said Soren. "They switch genes on and off. The instructions for making an eye are sitting right there inside your toe cell. Folded shut. Never read."

"Your toe is carrying the eye instructions around its whole life and just never opens them." Maya said it like she was tasting it. "Every cell in you is holding the complete plans for all of you. The whole body. Two hundred different kinds of cell, all walking around with the same book, each one only reading its own pages."

"About two hundred kinds, yeah."

Maya sat down next to him. For a second she was quiet, which almost never happened.

"Soren. The brine shrimp egg. It's one cell."

"One fertilized cell."

"One cell with the whole book. And it splits, and the copies are identical, same book, and then." She pressed both hands flat on the cookbook cover. "And then they start choosing which pages to open. And the ones that open the eye pages become eyes. And the ones next to them open different pages and become something else. From one cell. One book. Two hundred answers."

"It has to decide," said Soren. "At some point each cell decides who it's going to be."

"How does it decide?" Maya turned to him. "Who tells the eye cell to be an eye?"

Soren waited for himself to have the answer. He always tried to have the answer before he spoke. This time he turned the pages of the cookbook and watched them fall and did not have it.

"I don't know," he said. "Where it is, maybe. What's around it. The cells next to it."

"But the first time. The very first split. Two cells. Same book, same everything, same neighbors. What makes one of them eventually go one way?"

Soren stared at the two halves of the open book. The left page and the right page. The same paper. The same ink rules. And he understood, the way you understand the floor isn't there in the dark, that he had walked straight off the edge of what anyone had told him.

"I don't think that's a settled thing," he said carefully. "I think people are still working that part out. Right now. People with whole labs."

Maya's face did something he'd seen before, It wasn't disappointment that the question stayed open. It was the opposite.

"So a person could figure that out," she said. "That's a real question that doesn't have a finished answer. Somebody who keeps asking it could be the one."

"You ask it like that all the time," Soren said. "That thing you do. Where you say the true thing can't be true and it turns out the true thing was just two things."

Maya didn't answer. She picked the jar back up and held it to the light and looked at the brown dust that did not look like anything at all.

"Every one of those," she said softly, "is holding the whole plan for the whole animal. Folded up. Two hundred kinds of cell, asleep in a speck."

Soren wrote in his notebook: same book, different pages open. Then under it: who opens the first page? Then he left that line with nothing after it, on purpose, because some lines were better kept open.

The porch light hummed. In the jar, in the salt water, the first speck of dust unfolded a tail and began, very slowly, to move.