Neal Stephenson's newest (?) solo book, a couple years old at this point. Something blows up the moon, pieces start raining down, humanity is Doomed. A group of people survive in a space station and in a fleet of little modular ships that can dock w/ each other, link up, transfer stuff, etc. etc. Finally most people are dead but for 7 women and 1 (?) guy (this is kinda fuzzy, it's been several years since I read it). One of them is a geneticist. (Note that this is set in a basically modern-day Earth with equivalent scientific technology and know-how.) The geneticist has a plan: she'll eliminate every genetic disease from the women's eggs and modify them however they want - make them stronger, smarter, modify their limbs and bodies, etc. And she makes 7 human subspecies that apparently do not hybridize to any significant degree over the next several thousand years. Also humans who lived through the apocalypse in submarines apparently developed gills. Whoo, it just sets me on edge.