Yeah. The theory was that when a woman is gone from her husband for a period of more than three days, the actual sperm build up by hubby isn't because he *ahem* missed her, but because he has been genetically programmed to believe that she could possibly be away with another man. Therefore, upon her return, he produces an above average sperm count to seek and destroy another man's sperm in utero. But because the husband's sperm is on a killing mission- yes killer sperm seeking out another man's sperm (they showed this on film), he had less of chance of getting wifey pregnant than a potential lover. This was also tied to a woman biologically knowing when she was fertile, and her seeking out the best male for reproduction, which may not be hubby. In the end, the lover has the best chance at getting the woman preggers.
It was interesting, but I found it hard to believe we're slaves to biology and genetics. Our ability to think and rationalize makes us able to make better decisions than those driven by our reptilian brain. Well, some of us anyhow.