To rise, the Ythrians usually did a handstand during the initial upstroke. It took less than a second.

Then came video of them in a centrifugal grav chamber. Oh yes, they were slow and awkward afoot. The Prefect sighed at these sights. Rachel felt elated and saw that these sights fulfilled a hope none in the Library had expressed, but surely all shared: real live aliens.

The Prefect said softly, “Big and beweaponed, instantly ready to mount the wind, they need fear no beast of prey. Carnivores. Hunt in flocks. Farm only to get grain. They feed that lot to animals they then hunt and devour. Hence they maintain civilization without the need to crowd together in cities. Their townspeople are mostly wing-clipped criminals and slaves—or so they say. Today their wiser heads hope robots will end the need for that.” She had a thousand questions, but watching the Ythris move was more fascinating as Masoul went on, clearly enjoying his insights. Prefects were like professors that way.

“You ask where the power comes from to swing this hugeness through the sky? Oxidation of food, what else? In their enclosure we found the limiting factor to be the oxygen supply. A molecule in their blood can carry more than our hemoglobin does. The Ythrian has lungs, a passive system resembling ours. In addition he has his supercharger, evolved from the gills of an amphibian-like ancestor, which works in bellows fashion, the flight muscles connecting directly with the bloodstream. Those air-intake organs let him or her burn fuel as fast as necessary.”

“Hence the demand of each household for a great hunting or ranching area?” she ventured.

The Prefect nodded. “The social types say Ythri are as fundamentally territorial as we are fundamentally sexual, and we’d better bear that in mind. They’re carnivorous, aside from various sweet fruits. Carnivores require larger regions per individual than herbivores or omnivores do, in spite of the fact that meat has more calories and protein per kilo than most vegetable matter.”

Rachel looked dubious. “You—ah, they—think we should reason from origins to the present? Even though—”

“Consider how each antelope needs a certain amount of space, and how many antelope are needed to maintain a pride of lions. Earthers who call themselves Xenoists have written thousands of papers on the correlations between diet and genotypical personality, garnered from our Library translations.”

Rachel was still skeptical. She shook her head doubtfully.

“They missed the possibility of a race like the Ythrians, whose extreme territoriality and individualism—with the consequences to governments, mores, arts, faiths, and souls—come from the extreme appetite of the body.”

She wondered at this angle, so asked, “You’re hinting at…?”

“You need to get more exercise. They will expect you to conform to their flock social dynamics.”

“Which means…?”

The Prefect allowed himself a thin smile. “That shall be revealed. Earthside loves its secrets.”

Rachel disliked the gym. The same air had hung for months in the windowless volume, absorbing the smells of human sweat and breath, a concoction smell like roasted peanuts and beer, perfume and bay rum and hair oil and tired feet. A social researcher with a good nose could have written a PhD thesis about that air. But she did her workouts and swims and even simple one-handed push-ups, a hundred at a time. She huffed and puffed and sweated and slept and wondered…. Then came the Ythri.