Spillover: the powerful, prescient book that predicted the Covid-19 coronavirus pandemic.

by David Quammen

why are RNA genomes so small? Because their self-replication is so fraught with inaccuracies that, given more information to replicate, they would accumulate more errors and cease to function at all. It’s sort of a chicken-and-egg problem, he said. RNA viruses are limited to small genomes because their mutation rates are so high, and their mutation rates are so high because they’re limited to small genomes. In fact, there’s a fancy name for that bind: Eigen’s paradox. Manfred Eigen is a German chemist, a Nobel winner, who has studied the chemical reactions that yield self-organization of longer molecules, a process that might lead to life. His paradox describes a size limit for such self-replicating molecules, beyond which their mutation rate gives them too many errors and they cease to replicate. They die out. RNA viruses, thus constrained, compensate for their error-prone replication by producing huge populations and achieving transmission early and often. They can’t break through Eigen’s paradox, it seems, but they can scoot around it, making a virtue of their instability. Their copying errors deliver beaucoup variation, and beaucoup variation allows them to evolve fast.