What would you do if you contracted a "disease" that forced you to seek out the uninfected and infect them? We've had plenty of examples of this in popular culture lately to help us think about the issue-28 Days, 28 Days Later, and I Am Legend have all dealt with the aftermath of an epidemic that forces us to lose our humanity in the mindless quest to propagate a disease over which we have no control. I've always seen these stories as allegory for human creations gone awry, as apocryphal tales of what will happen in humans continue to change nature to meet our demands.
While this may sound an awful lot like the other examples of this theme that I mentioned, what makes Butler's take different is the way that the infected try to hold on to their humanity. The organism living inside each of them causes them to have compulsions that are immoral by human standards-incest, rape, murder. But Eli is convinced that if they can keep their settlement small, and only take new people as necessary to keep their compulsions at bay, then they can retain their humanity and contain the infection. In Clay's Ark the literal infection is an alien life form, but Butler could be using that as a symbol for anything that causes us to act in ways that deny our humanity. Rather than experiencing the invasion from the perspective of the "clean", we see this outbreak from the point of view of the infected. Eli is basically struggling with the most basic existential questions. What is it that makes us human, what is it that defines us as a human race? And once the infected start having children who are very different than human children, what can be said for the future of the human race? Are the children a new species of human, or something altogether different? And does it matter, if they are taught how to act as humans? Clay's Ark may be a pretty short novel, but Butler gives us a lot to think about. The next book in the Patternist series takes us to the far future, and I find myself wondering whether I will like where this story comes to its natural conclusion.