Fareed Zakaria

What do cells do when they see a broken piece of DNA? Cells don't like such breaks. They'll do pretty much anything they can to fix things up. If a chromosome is broken, the cells will repair the break using an intact chromosome.

The historical novelist has to consider what has actually happened, while the SF writer is dealing in possibilities, but they are both in the business of imagining a world unlike our own and yet connected to it.