Vicki nodded with a sigh. “His room is practically papered with prints that he’s downloaded. It’s like one of those science-fiction-movie theme parks. I think he must have checked out every book on them in the local library.”
“I hope that won’t mean more additions to the private zoo, CR,” Keene said, looking at Robin. Keene had dubbed him Christopher Robin, after the character from the British children’s books.
Robin appeared to mull over the possibility, then shook his head. “Too much cleaning up after. And they’d probably bother the neighbors.”
“What’s this I hear about them not being real?” Keene asked. “Has everyone been imagining things all these years?”
“Oh, did Mom tell you about that?”
“Right.”
“Theoretically they ought to be impossible,” Robin agreed. “They couldn’t exist.” Keene waited, then showed an open palm invitingly. Robin went on, “Well, you’re an engineer, Lan. It follows from the basic scaling laws. The weight of an animal or anything increases as the cube of its size, right?”
Keene nodded. “Okay.”
Robin shrugged. “But strength depends on the cross-section of muscles, which only increases as the square. So as animals get bigger, their strength-to-weight ratio decreases. All this stuff you read about insects carrying x times their own body weight around isn’t really any big deal. At their size you’d be able to walk around holding a piano over your head with one hand.”
Keene glanced at Vicki with raised eyebrows. “Robin’s been doing his homework.” Keene was familiar with the principle but had never had reason to dwell on its implications regarding dinosaurs.
“That’s Robin,” Vicki said.
Keene looked back at Robin. “Go on,” he said.
“As you get bigger, it works the other way. Do you know who the strongest humans in the world are?”
“Hmm. . . . Oh, how about an Olympic power lifter?” Keene guessed.
“Right on. Now, take one, say, doing dead-lift or a squat. The most you’d be talking about would be what—around thirteen hundred pounds including body weight?”
Keene shrugged. “If you say so. It sounds as if you’ve checked it out.”
“Oh, he has,” Vicki threw in.
“Now scale him up to brontosaurus size, and his maximum lifting capability works out at under fifty thousand pounds,” Robin said. “But the brontosaurus weighed in at seventy thousand; the supersaur even more than that, and the ultrasaur at—would you believe this—three hundred sixty thousand pounds!”
“My God.” Keene sat back in his chair, staring hard as the implication finally hit him. “Are you sure they were as heavy as that?”
Robin nodded. “I got those estimates from a guy called Young, who’s Curator of Vertebrate Paleontology at the museum in Toronto. And I checked it with somebody else at the Smithsonian, too.” It sounded as if Robin had been picking up tips from Vicki. His expression remained serious. “But the point is, the strongest man in the world wouldn’t have been able to stand under his own weight, let alone move—and that’s when you’re talking about practically being made of muscle. These other things were all digestive system. So how did they do it? See what I mean—they couldn’t exist.”
Keene looked across at Vicki quizzically. It was a challenge for any engineer. Vicki tossed out her free hand and shook her head. “Maybe they had better muscles,” Keene offered as a starter, looking back at Robin.
Robin was clearly prepared for it. “No, that doesn’t work. The maximum force that a muscle can produce is set by the size of the thick and thin filaments and the number of cross-bridges between them,” he replied. “It turns out they’re about the same for a mouse as for an elephant—and it holds true across all the vertebrates. That means the only gain you get from larger size is what comes from the bigger cross section.”
“There’s no increase in efficiency,” Keene checked.
Robin shook his head. “In fact, it goes the other way. Gets worse.”
“Okay. . . .” Keene searched for another way to play devil’s advocate. “They were aquatic. I saw a picture in a book once that showed them snorkeling around in lakes and swamps.”
“Nobody believes that anymore,” Robin countered. “They don’t show any aquatic adaptations. Their teeth were worn down from eating hard land vegetation, not soggy watery stuff. They left tracks and footprints. That doesn’t happen under water.”