“The sole behavioral element which appears to be not easily explicable by postulates concerning environment and accidental historical developments, is the cannibalistic puberty rite. According to the anthropological computer, this might well have originated as a form of human sacrifice. But that computer notes certain illogicalities in the idea as follows.

“On Old Earth, sacrificial religion was normally associated with agricultural societies, which were more vitally dependent on continued fertility and good weather than hunters. Even for them, the offering of humans proved disadvantageous in the long run, as the Aztec example most clearly demonstrates. Lokon has rationalized the practice to a degree, making it a part of the slavery system and thus minimizing its impact on the generality. But for the lowlanders it is a powerful evil, a source of perpetual danger, a diversion of effort and resources that are badly needed for survival. It is not plausible that the custom, if ever imitated from Lokon, should persist among every one of those tribes. Nevertheless it does. Therefore it must have some value and the problem is to find what.

“The method of obtaining victims varies widely, but the requirement always appears to be the same. According to the Lokonese, one adult male body is necessary and sufficient for the maturation of four boys. The killer of Donli Sairn was unable to carry off the entire corpse. What he did take of it is suggestive.

“Hence a dipteroid phenomenon may have appeared in man on this planet. Such a thing is unknown among higher animals elsewhere, but is conceivable. A modification of the Y chromosome would produce it. The test for that modification, and thus the test of the hypothesis, is easily made.”

The voice stopped. Evalyth heard the blood slugging in her veins. “What are you talking about?”

“The phenomenon is found among lower animals on several worlds,” the computer told her.

It is uncommon and so is not widely known. The name derives from the Diptera, a type of dung fly on Old Earth.”

Lightning flickered. “Dung fly—good, yes!”

The machine went on to explain.

9.

Jonafer came along with Moru. The savage’s hands were tied behind his back, and the spaceman loomed enormous over him. Despite that and the bruises he had inflicted on himself, he hobbled along steadily. The clouds

were breaking and the moon shone ice-white. Where Evalyth waited, outside her door, she saw the compound reach bare to the saw-topped stockade and a crane stand above like a gibbet. The air was growing cold—the planet spinning toward an autumn—and a small wind had arisen to whimper behind the dust devils that stirred across the earth. Jonafer’s footfalls rang loud.

He noticed her and stopped. Moru did likewise. “What did they learn?” she asked.

The captain nodded. “Uden got right to work when you called,” he said. “The test is more complicated than your computer suggested—but then, it’s for Donli’s kind of skill, not Uden’s. He’d never have thought of it unassisted. Yes, the notion is true.”