Survival of the fittest is, at its heart, an expression of the idea that natural selection will favor those species that are best adapted to their environment. But there might also be a place for the unfit after all.
Natural selection and survival of the fittest are often seen as synonymous, even if the truth is a bit more complicated. Still, whatever its origins, the term is a useful encapsulation of one of the driving forces of evolution...except when it isn't, as researchers at the UK's Universities of Exeter and Bath recently discovered. In certain situations, the unfit don't just survive, they thrive.