In the universe described in "The Ghost Brigades" by John Scalzi, there are planets where life forms have developed genetic frameworks that bear a resemblance to those found on Earth. These extraterrestrial species utilize nucleotides akin to those that underpin terrestrial genetics, suggesting a possible connection between them and Earth's biological processes.

This genetic similarity raises intriguing implications, as it has been noted that some intelligent species from these planets have also been known to prey on humans. The narrative hints at a darker aspect of these genetic parallels, showcasing an unsettling dynamic between different intelligent life forms across the universe.