“How many muggles are there in the world today, in your opinion? I know you would know about those things”, she asked when they sat in the hallway. She looked him straight in the eyes, completely focused on the argument, while her body automatically did its thing. In this case, she held his right hand and doodled something on his palm with her index finger. Harry thought she didn’t even notice, and he realised that, for the most part, he didn’t either. For them, this level of casual physical contact was the baseline. He was never this physically intimate with anyone else, but Lyra was different. She was just Lyra. She would hammer his head into the wall when playing Quidditch, or fall into his embrace when afraid of something in the woods. They just didn’t find it strange, or awkward.

“Oh, almost seven billion, I guess”, he shrugged. The number was growing and he didn’t actually have the current count.

“So, how many of those seven billion are wizards?”, she proceeded, holding his one hand while resting her other hand on his knee.

“I’m the wrong person to ask; I think Ministry should know”, he shrugged.

“They do, in fact. My father got me the numbers. The number is around five hundred muggle born wizards per seven billion muggles”, she pressed. “This makes probability of a muggle-born wizard like your mom or Hermione a one in a fourteen million event.”

“Wow”, Harry scratched his scar. “This is really low odds”.

“Exactly”, she nodded, doodling unconsciously on his knee. “The probability of non-magical offspring from two magical parents is somewhat below one in a hundred. Now, please tell me what it means.”

“It means that introducing fully muggle genetics into the magical community would exponentially increase the probability of squibs, eventually diluting the magical genetics until the point of disappearance, or at least non-viability of the community because of low population numbers”, he conceded, squeezing her hand slightly. “It gives legitimacy to your argument, if that’s how that actually works. However, what if muggle-born magical children have concentrated magical genes already? In that case, dilution would not be an actual threat”, he countered.

“I hear you”, her palm got slightly sweaty as she stressed over the argument, lost in thought, her eyes moving as she thought about it in real time. “Your argument is that your mother, and your Granger friend, are both extraordinary witches. They are not just average. I heard only praise about your mother, from highest places. She was a generational talent. Granger is smarter than both of us together, I think. They look like highly concentrated magical essence, not like something that would dilute pure blood. However, is manifestation of genes an indication of actual genetics? What if they merely scored a combination of recessive genes manifesting a phenotype, and it would not carry through to the next generation?”, her eyes were calm now, boring holes through his, and she intertwined their fingers.

“That’s actually a good point, and I don’t know the answer”, Harry nodded. “However, I have some empirical data. My mother was muggle-born. My father was a pure-blood wizard from an ancient line. I turned out pretty well, if I may say so myself”, he smiled.

“You turned out perfect in every way”, she smiled back, as he blushed. “However, you might be merely a statistical anomaly, and it’s a single data point. You look like you won the genetic lottery, having the best of both and no apparent drawback other than the poor eyesight. However, are you a rule, or are you an exception?”, she pushed back, doodling on his knee.

“Well, do we have data about frequency of squib births in pureblood families, vs. mixed blood?”, he countered.

“Now, that’s a pickle. It seems to be a Poisson distribution issue. We don’t actually have a good data pool on either side, considering the low absolute population metrics”, she shrugged, drawing eights on his knee.

“So, you don’t really know if there’s an actual problem, or is it a storm in a teapot? And we’re actually having a war over this?”, he smiled, playing with her hand.

“Well, it’s potentially an extinction-level problem for the wizarding community, so it warrants extreme concern. However, your argument, that an internecine war is a more urgent extinction-level problem that we seem to be rushing into, and is actually worse, with certainties rather than probabilities, is valid”, she nodded and smiled.

Hermione was passing by in the hallway, looked at them, smiled, rolled her eyes and proceeded to her arithmancy class.

“What, Granger?”, Lyra growled.

“Ten points from both Gryffindor and Slytherin for the two of you not getting a room”, Hermione replied in a convincing imitation of Snape.

“Huh?”, Lyra shrugged, looking at Harry completely clueless, while he blushed.

“She’s just weird”, he shrugged. “Let’s go to class”.