What the dinosaurs see, know, but will never, can never tell is that it's all mutual. All of it. Even though most of it will go forever unexpressed. But it's all mutual, all the arrows run both directions, the energy goes both directions, all the time, all the time.
Zoe feels it most strongly when she's not wanting babies. She gave that up, a long, long time ago, that biological urge to reproduce—back during some fight or another, some escape-with-their-lives-and-nothing-else—gave it up so she could keep her clarity, keep her focus. And it works, mostly. Except when it doesn't.
That'll be the times when the dinosaurs watch her hold back tears, when they see her there, standing behind Wash as he executes some tricky landing, or makes fun of Mal's stiff Captain Tightpants demeanor, or when he's just playing around with them, his dinosaurs, with the black on the other side of the window, and her looking at him, watching him, and hearing the children she'll never have with him say "Daddy, Daddy, tell another stooooooo-ry!" in their traveler's accents made up of a bit from each planet they've ever been to. The times when she puts her hands on Wash's shoulders, just for a moment, and he reaches up with one hand and grasps hers, or prances a dinosaur's foot over her arm; the times when, if she hadn't given it up, she'd swear she'd be on the road to maternity after they retire to their cabin.
But she's given that up long ago, and only the dinosaurs know how much that cost her, and how much it gained her, and that she's satisfied with her choice even when the sorrow comes back, for a moment, for a day.
What Mal tells the dinosaurs is something else altogether. He goes on and on at them about the damn Core hypocrites, about the Reavers, about the Alliance, about the fools, planet to planet, who make "A little honest trading" nearly impossible. He never talks about the way he feels when Zoe puts her hands on Wash's shoulders like that, the way he wishes, sometimes, it were his shoulders instead. That's just feng le, that kind of thinking—she's his second, had his back all this way, all this time—and she's not his type, nor he hers. And anyway, there's Wash to consider.
What the dinosaurs know about Mal is how he spends an hour here, an hour there, watching Zoe work—not looking at her body, or thinking of his hands on her, but watching her work—admiring her mind, how she sets it to a problem and goes through it, step by step, leaving nothing out, until she can sort it in her head as fast as she can break down and put together any piece of arms Serenity carries, until she can put it into action as quickly as she can put Jayne in his place and leave him there standing stock-still and dumbfounded.
What Mal doesn't tell even the dinosaurs is how he sometimes dreams of lying between them, Wash and Zoe—how he wakes tangled in his sheets thinking it'd been their arms around him, and he'd not been falling, always falling, alone, into the black, no one to catch him, no one to carry him to his rest if he needs that, when he needs it. He doesn't say this to the dinosaurs as he turns them in his hands, seeking clues to whether Wash would understand if he backed him up against the bulkhead and took a kiss, just took it—just once—to see what it is Zoe knows that Mal doesn't about Wash. He doesn't tell the dinosaurs, but they know anyway, they feel it in the heat in his hands when he makes them rut on the dashboard of the controls, when he has them fight it out and knock over the lone tree, found in a mess of children's stuff scavenged off some junked freighter once, long ago.
What the dinosaurs don't tell Wash is what to do. They know, but it needs to come from him, so they just wait, just let him figure it out his own seeming slow-witted self, his own quick-to-pick-up, slow-to-admit self, how much he needs to feel that there're no loose ends, that everything could be picked up, that they could carry on, if something happened to any of them. He sees how it goes, how ill it goes if one becomes isolated, like Simon would've if Kaylee'd not got onto him, or like Jayne if River didn't bedevil him just to keep him sane, connected. It's like Kaylee says about the engine—ship can't fly if the engine don't got all her parts; to Wash's mind that's true of the crew, too. Can't keep a working ship if the Captain's all out there on his own, all lost by hisself, without anyone to hang on to.
Wash watches Mal and Inara dance round and round, sees how Simon looks at Mal and looks away again, looks toward Kaylee; notices the little comments Zoe makes, just common sense, and how Mal reacts like she was kin or closer. One thing Wash understands real well is orbits, and how there's got to be a center or the orbits don't hold.
Another thing he understands real well is changing trajectory to work with changing conditions—so when he comes upon Mal one day in the cabin there, playing with the dinosaurs, muttering curses and imprecations about some dang thing or another, he doesn't wisecrack or act like he doesn't notice—he puts his hands on Mal's shoulders the way Zoe does on his, and smiles when Mal first stiffens, then relaxes, then dances a dinosaur across his knuckles, then leans back and rests his head on Wash's belly.
"They make it easier, the black," Wash says.
"These critters? Reckon they do at that," Mal says.
Zoe comes in, then, and sees this, Wash supporting Mal, Mal being comforted by Wash, in this unthreatening, completely vulnerable way. And smiles to herself, and nods—at some point, then, she'll have to bring up the idea that the wall between their cabins is not a bearing wall, and how little it would take to cut a door in it, or take it down altogether, and how much easier that would make it, for what she's been wanting. If she's not going to have children—and she's not—she's damn sure not going to be worrying about what Wash'll do if something happens to her—or what Mal would do, if it'd come to that—and it might, it might.
And oh, forbid, forbid, if anything happens to Wash—oh, forbid it—but she wants to know she can't wall herself off from everyone—and only way to do that is to make sure the opening's there now. She's not sure what Book would say, but she's pretty sure River would just smile, and look at the dinosaurs, and say, "See? I told you they were listening," and cock her head at the three humans, and laugh.
Dinosaurs may be extinct, but that doesn't mean they aren't alive and kicking on Serenity. Sometimes they know more than anyone else what's going on up there in that flight deck.