The Natural History of the Sexual Genome: proactive drivers and passive drifters

Two authoritative treatises have recently addressed the evolutionary origins of the eukaryotic genome’s many surprising architectural features, such as the fact that more than 50% of the DNA in various species is made up of active or retired transposable elements.Austin Burt and Robert Trivers describe diverse tactics by which seemingly selfish pieces of DNA actively spread and persist in populations of sexual reproducers and thereby generate extensive intragenomic (intergenic) strife. Michael Lynch, by contrast, emphasizes how even deleterious mutations can passively drift to fixation in small populations. The worldviews in these two books may seem fundamentally at odds, but they share a powerful notion that all eukaryotic genomes are like intracellular ecosystems, the natural histories of which are fundamental to how sexual genomes evolve.