The Church on Spilt Blood in St. Petersburg, Russia, is like something out of a fairy tale. Perched on the edge of a frigid canal, it has a forest of onion domes that stretches toward the sky and pastel-colored mosaics that cover every square inch of the interior. This is not the type of place where paleontologists typically hang out, but I was in town to study a new dinosaur, and I insisted on taking a detour. The visit was personal. The church was built on the spot where Czar Alexander II was assassinated by revolutionaries in 1881, setting in motion a sequence of events that led, eventually, to me. The czar's death ushered in a frenzy of anti-Jewish pogroms. Jews on the edge of the Russian empire grew frightened, and a family in Lithuania panicked and sent their young son to safety in America. That man was my great-grandfather. If not for that chain of dominoes that began more than 100 years ago in St. Petersburg, I would not be here today.