All about levels: transposable elements as selfish DNAs and drivers of evolution

The origin and prevalence of transposable elements (TEs) may best be understood as resulting from “selfish” evolutionary processes at the within-genome level, with relevant populations being all members of the same TE family or all potentially mobile DNAs in a species. But the maintenance of families of TEs as evolutionary drivers , if taken as a consequence of selection, might be better understood as a consequence of selection at the level of species or higher, with the relevant populations being species or ecosystems varying in their possession of TEs. In 2015, Brunet and Doolittle (Genome Biol Evol 7: 2445–2457) made the case for legitimizing (though not proving) claims for an evolutionary role for TEs by recasting such claims as being about species selection. Here I further develop this “how possibly” argument. I note that with a forgivingly broad construal of evolution by natural selection (ENS) we might come to appreciate many aspects of Life on earth as its products, and TEs as—possibly—contributors to the success of Life by selection at several levels of a biological hierarchy. Thinking broadly makes this proposition a testable (albeit extraordinarily difficult-to-test) Darwinian one.