Imagine a mountain range where height represents an organism's fitness. Every point on the slope is a particular set of genes. Evolution climbs upward, but the terrain of this phylogenetic network landscape is cut by ridges and valleys. One wrong move, and a mutation can send a species tumbling into the abyss of extinction.
Nature has a hack. Many changes in DNA don't affect the organism at all, like a trail running across a flat plateau. Such neutral mutations create vast networks where you can wander without losing altitude. Sooner or later, a traveler stumbles upon a new incline and climbs higher. Evolution doesn't get permanently stuck in local pits: it simply goes around them.
The authors of the review propose a new way to measure the traversability of such landscapes — based on actual evolutionary outcomes, not abstract maps. They also remind us: the path to the summit is not always straight. Sometimes a step sideways or even a temporary descent opens the way to new heights. At the end of this journey, a species ends up where it couldn't have gone by moving only upward.
If all mutations were harmful, evolution would stop. Neutral changes act as spare passages in a maze, allowing hidden diversity to accumulate for future leaps.
In "Jurassic Park," resurrected dinosaurs quickly adapt to a new world: their genetic landscape turns out to be rugged enough to find unexpected paths.