Nocturnal: A Novel

Robin laughed and shook her head. “Sure, Pooks, sure. It’s a female, so her gamete can only carry an X.”

She put the letter from each column header into the boxes below it, then added the letter from each row header, “So we wind up with two possible combinations of XY, two of XX. On average, half the kids will be male, half will be female. Got me so far?”

All three men nodded.

“Now we saw that the Blackbeard was just that, a guy. His sex chromosomes were Zed-X. Normally, the Y chromosome codes for male, but testicles or no testicles Blackbeard had a beard and a penis, so he’s a guy. That means the Zed chromosome has to have some elements of the Y chromosome.”

She drew a new four-squared box. She drew XZ across the top, then on the left she drew two Xs. She filled in the squares, resulting in two with XX and two with XZ. “So, if Blackbeard had functional sperm — which he could not have had without testicles — he would produce these possible offspring. You guys see the problem with this?”

Bryan pulled the pad in front of him. “There’s no YZ,” he said. “Oscar Woody’s killer was YZ.”

“Bingo,” she said. He’d always been so good at putting pieces together. “To get a Y-Zed, we have to have a female who can provide a Zed chromosome.”

Pookie reached out and tapped the pad. “Couldn’t the YZ — Oscar’s killer — couldn’t that be a female?”

Robin shook her head. “In primates, every instance of a Y chromosome means male. This includes XXY, which is Klinefelter’s and for the sake of argument is always male, and XYY syndrome, which also results in a male. We have to assume that Oscar’s killer is male, not female.”

Robin drew a third Punnett square, this time with three columns and two rows to make a total of six squares instead of four. “That brings us to Rex, who is X-Y-Zed. Every one of his sperm cells had what is called non-disjunction, which means they had two sex chromosomes. Primate sperm cells are supposed to have just one.”

Above the columns, she wrote XY, XZ and YZ. On the left side, she drew Xs next to the rows. She turned it so the boys could see.

Bryan leaned in for a closer look. “If someone like Rex had a child, the child gets … what … one chromosome from the mother, two from the father? The mother would always provide an X, and all his children would have three sex chromosomes instead of two, right?”

Robin nodded. “That’s right. Three sex chromosomes is called trisomy.”

Bryan again pulled the pad in front of him. “Well, since the only other two Zed examples we have are not trisomal, that means someone like Rex couldn’t be their father.”

“You got it,” she said. “So, if Rex mates with a woman …” She pulled the pad back in front of her and she filled in the six boxes: two XXYs, two XXZs, two XYZs. “The XXY is Klinefelter’s. I have no idea what an X-X-Zed would be, but maybe it’s a female version of Rex. We know Rex was an X-Y-Zed, so at least in Rex’s case, X-Y- Zeds appear to be normal people.”

Bryan stood and walked to the kitchen. “So Rex could make more Rexes,” he said as he pulled four fresh beers from the fridge. “But someone like Rex can’t make an XZ or a YZ.” He opened all four bottles and passed them out before he sat. “So what makes those combinations?”

“Now for the really crazy part,” Robin said. She’d walked them through the other Punnett squares to introduce the basic concepts. Now they were ready for the bomb to be dropped.

She turned to a fresh piece of paper and drew a box with two columns and three rows. She put an X and a Y above the columns. To the left of the three rows, she drew an X, a Z and then a second Z.

Pookie rolled his eyes. “Sorry to be a downer, Robin, but this is kind of boring. Can you get to the point?”

“I’m almost there,” she said. “Just bear with me. Say the father is a normal male” — she circled the XY — “and the mother is X-Zed-Zed” — she circled the XZZ. “Let’s say that — unlike Rex — this X-Zed-Zed mother can give only a single chromosome to her gamete” — Robin filled in the squares as she talked — “then you can get the X-Zed combination of the Blackbeard and the Y-Zed combination that killed Oscar Woody.”

“Ewww, that’s nasty,” Pookie said. “You’re saying the two killers we know about, they have a mutant-Zed-chromosome mommy who is getting it on with regular dudes?”

Robin nodded as she finished the Punnett Square: two XZs, two YZs, an XX and an XY. “You could even wind up with normal boys and girls. But what you couldn’t get is another X-Zed-Zed. There’s only one way to get that. Now, at the Oscar Woody killing, someone painted Long Live the King on the walls, right?”

Bryan nodded. “Yeah, and I think Rex is the king in question.”

She looked at John. “You were waiting for a punch line? Here it is, but I don’t think it’s all that funny — if you have a king, maybe you also have a queen.”

Robin flipped to a new page and drew — three columns and three rows for nine squares total. “So, you take a king” — she marked the columns XY, XZ and YZ — “and a queen” — on the left side, she marked the first row X, the second and third each with a Z — “and something interesting comes up.” She filled in the boxes, making an alphabet soup of combinations: two XZZs, two YZZs, three XYZs, an XXZ and an XXY.

She circled the two XZZs.

Bryan looked up, the expression on his face one of shocked realization. “If the XZZ is a queen, then the only way to make a new queen is for her to mate with a king.”

“Exactly,” Robin said. “If this is the way it works, then you have a eusocial structure with a breeding pair.”

John shook his head in annoyed denial. “Wait a minute. Kings? Queens? Not like English royalty kings and queens but like … termites? Eusocial means one breeding pair producing all the offspring for an entire colony, like ants and bees, right?”

Robin nodded.

“Rex and the others are people, which means they’re mammals,” John said. “Eusocial creatures are insects.”

“There’s at least two species of eusocial mammals,” Robin said. “The naked mole rat and the desert rat. They have a single queen, breeding males, and the rest of the colony are sterile workers.”

Pookie pulled the pad in front of him. “I could live with fleshy-headed mutants, I really could, but come on … a king? A queen? Besides, ant colonies have more than just kings or queens, they have workers and drones, right?”

“Right,” Robin said. “Those are called castes. There’s one more caste you didn’t mention. Blackbeard had no testicles. He was sterile, couldn’t have passed on his genes to a new generation. But he was strong, he was dangerous, and he could heal fast, which would let him recover from damage. Guess which caste is most likely to get damaged?”

Bryan stared at her. His eyes widened. He leaned back. “Holy shit.”

Pookie looked back and forth from Robin to Bryan. “What? Come on, tell me.”

Bryan sagged in his chair. “She’s saying Blackbeard is like a soldier ant,” he said. “Soldier ants can’t breed — they just live to protect the colony.”

They all sat in silence. Robin felt better for having shared the strange hypothesis. It was the only thing she could find to explain the limited data they had.

Pookie took a long drink of beer, then let out a belch. “Attack of the ant-people,” he said. “Awesome. Just awesome. But then what’s with the costumes?”

Robin picked up the pen, started making a random, back-and-forth doodle on the pad. “The costumes might be there to hide physical deformities. We really have no idea what we’re dealing with. The thing is, I think those teeth marks on Oscar Woody were exactly that — teeth marks. Not some tool designed to look like teeth. If that’s true, we’d be talking about someone with a wide mouth and two big incisors, so big you’d see it instantly. Maybe the masks and blankets hide more physical abnormalities?”

Bryan shook his head, so slightly Robin wasn’t even sure if he knew he was doing it.