Instead of studying fossils of long dead critters like any respectable paleontologist Fortey focuses on the survivors—“messengers from deep geological time”--that should not have survived at least 5 mass extinctions. There are the titular horseshoe crabs and velvet worms, of course, but also jellyfish, clams, bacteria and “slimy mounds” (stromatolites). And we must not forget the cockroach. Like a wise old grandfather who knows all things old and fascinating (and much more besides) Fortey guides us through 4 billion years of life.