The Heechee didn't waste that space. It was the most convenient place for a Heechee to carry anything, so the sorts of loads human beings would be likely to lug in their arms or on their shoulders the Heechee carried slung between their legs. In fact, all civilized Heechee carried a large, tapering pouch there. In it they kept two main items-the microwave generators they needed for their comfort, and the storage facilities for the 'ancient ancestors' whose minds they carried around with them, as a human being might carry a pocket calculator-as well as their equivalents of fountain pens and credit cards and photos of their near and dear. And when the Heechee sat down, what they sat on was the pouch.
(Thus at one blow ended a half century of speculation on why the seats in the Heechee spacecraft were so user-unfriendly for human users.)
Although hard and shiny, the Heechee integument was not
thick. You could see the movement of the bones through it; you could even see the muscles and tendons working, especially when the Heechee was excited-it was a kind of body language, something like a human's grinding his teeth. Their speech was somewhat hissy. Their gestures were not at all like those of Earthmen. They didn't shake their heads in negation; they flapped their wrists instead.
The Heechee had descended from a race of burrowers like prairie dogs rather than arboreal tree climbers moved to the plains, as people had. Therefore the Heechee possessed several traits that their heredity had laid on them. No Heechee ever suffered from claustrophobia. They liked being in enclosed spaces. (That may have been why they enjoyed tunnels so much. It certainly was why they preferred to sleep in things like gunnysacks filled with wood shavings.)
Their family lives were not exactly like those of humans; nor were their occupations; nor were their equivalents of politics, fashion, and religion. They had two sexes, like people, and sex was sometimes obsessive in their minds-as with people-but for long periods they hardly thought about the subject. (Not very like most people at all.) Strangely, they had never evolved equivalents of such human institutions as a government bureaucracy (they hardly had a government) or a financial economy (they didn't even use money in any important sense). Humans didn't understand how they could operate without these things, but the Heechee thought that in those respects human ways were pretty repulsive, too. Since, by the time human beings got far enough out into space to have some chance of encountering Heechee, most employed human persons were in these 'white-collar' occupations, they were startled to find that most Heechee were, in their view, unemployed.
It wasn't just that the human poli-sci and sociology professors wondered how the Heechee managed to get along without kings, presidents, or maximum leaders. Even on Earth, generations of anarchists, libertarians, and small-is-beautiful philosophers had been claiming that human beings didn't need such things, either. The real puzzle was how the Heechee had escaped having them anyway.
It took a number of anthropologists and cultural behaviorists a long time to come up with an explanatory theory. That phenomenon, too, seemed to have an evolutionary basis. It came from the fact that the pre-Heechee nonsapients-the primitive species they labeled 'Heecheeids'-had burrowed in the ground like prairie dogs or trapdoor spiders. They did not form tribes. They staked out territories. Therefore Heecheeids did not conduct tribal wars or struggle for succession to a throne; there wasn't any throne to succeed to. No Heecheeid ever had any need or desire that conflicted with any other Heechee-as long as the other guy stayed out of his territory.
Of course, you can't build a high-tech, spacefaring civilization out of solitary, noninterfering individuals. But by