"Look," Baxter said, "would you mind explaining what this is all about? I dunno about this guy, but I haven't heard anything about what this test actually involves."
The doctor looked at him curiously. "Didn't the receptionist give you the brochure?" he asked. "You're helping us test the survivability of a new species."
"What!?" the other subject yelled. Baxter blanched. "S-survivability?"
"Oh, don't worry," the doctor said. "You won't be in any danger; we'll have a crack medical team ready to assist you if something goes wrong. What we're mainly interested in is seeing how the average human adapts to a new body and new environment."
"Huh?" Baxter stammered. It was a little difficult to concentrate, as he was feeling a little woozy. "Why do you need to know that?"
The scientist smiled. "Glad you asked. You see, the simple fact is that the Earth can only support so many people. There's an upper limit to how many people can comfortably live off one planet's resources. Now, we're nowhere near that limit at present, no matter what the panic-mongers in Washington might tell you. But at some point in the future, people are going to have to deal with that, and organizations like ours intend to be ready for the future instead of getting blindsided by it."
Baxter was staring at his fingers, which seemed to be getting shorter, as the metacarpals in his hand were getting longer, stretching the skin between them. What was going on here? He stared, dumbstruck, as the scientist continued. "The obvious solution, which will doubtless be taken in the future, is for humanity to take to the stars. What we intend to do is lay some groundwork for that eventual exodus of humanity."
Now the skin on his arms was stretching out as well. Baxter's fingers were almost gone, and the skin on his arms was covered with little goosebumps. He could feel them forming on his lower body as well. And as he panicked, the scientist yammered on. "You see, while the human form is marvelously adapted for life on Earth, not every potentially habitable planet is sufficiently Earth-like for humanity, as it presently is, to be the best-suited life-form. Of course, it's possible to set up artificial terran environments for humans to live in, and those future star-colonists will doubtless be better at it, but it's still a waste of resources that severely limits how many people a planet can support."
There was a sharp, prickly feeling on various parts of Baxter's skin, and tiny little projections began to sprout from the goosebumps. Suddenly, this all clicked in Baxter's mind with memories of his grandpa's poultry farm and the many plucked chicken corpses. Holy crap, was he growing feathers? He wanted to ask, but the monologuing doctor was clearly off in his own little world. "And so, our solution is to adapt the colonists to fit their new environment. Naturally, there would still be artificial environments for any visiting normal humans, but allowing the population of a new world to fit in seamlessly would make things infinitely more efficient."
Baxter could only stare as his arm turned into a rudimentary wing. Oblivious, the scientist continued his lecture. "But the one thing we're not sure of is this: how would they handle it? That's where you come in. You, two humans of average intelligence, with no skills or knowledge applicable to the feral environment in which you will be placed, are going to help us find out just how adaptable the human mind is."
Baxter's mind was reeling; he was turning into some kind of mutant bird freak, and all this guy could think about was his grand speculation on humanity's future! He slumped to the floor. Just before unconsciousness claimed him, Baxter heard the scientist speak. "Oh, for crying out loud," he said, "and just when I was nearly finished!"