Literature and Evolution

I haven't read Brian Boyd's Literature and Evolution: a biocultural approach, and don't intend to. But I've read a number of reviews, including Terry Eagleton's in the latest London Review of Books. And reading that, it occured to me: how do we in fact know that literature is part of the species's apparatus for survival, an tool for adaptation? Mightn't it in fact belong to those of our capacities which will in the end kill us off? Let's not forget that in the end we won't survive, and in not surviving will join most other species that have ever come into existence.