"Uh." Well, that was an abrupt return to earth. Cosima's less sure of her footing here, but offers: "A lot of people actually can't have biological children. It's not super uncommon. But it does seem like there's a genetic component, with us in particular. As far as I know, Sarah's the only one of us to give birth. But on the other hand, not all of us have tried."

She glances at Sarah. "It's possible I figured out more about it, back home, but science is kind of slow going here."