There was no reason to expect that she had been monogamous. One man or another would be all the same to her, if they could leave this area. If she wouldn't find the corpse of her mate. Jason took her hand, and they walked. They walked for a long time. Then they slept, then ate, then walked again. The woman jabbered. Jason Wall talked. He was enjoying himself immensely. There was no hurry. This was a new kind of life, a new kind of experience. He loved every moment of it.
They found another cave, three day's journey from the first. They lived there for some weeks. The pain came more frequently, but Jason Wall withstood it.
The weeks became months. His days were numbered now, he knew that. It seemed just, somehow. After taking all that the first woman had to offer, he would kill her—and destroy all humankind.
She never had understood his affliction, his great pain. Pain from a wound she could understand. Once he had scraped his knee on a rock, and she had been extremely sympathetic. But pain from disease seemed unknown to her. Of course, Jason Wall knew, any disease was compounded of two things: a disease agent, bacteria or virus, and a susceptibility. Apparently First Man and First Woman had utterly no susceptibility. They were disease-free.
Some time later in the course of human development—how much later he did not yet know—susceptibility to disease had evolved.
The woman's belly grew round and Jason Wall knew she was going to have a baby. His baby.
He sighed. His time was short. The baby would never be born, because he would kill its mother first.
Then it struck him like a blow. A baby. His baby. And First Man and First Woman—free of disease. He had introduced disease into the human makeup, by planting his seed in this woman!
Including his own....