‘Life: a genome's way of making more and fitter genomes’ provides a global perspective of terrestrial biology. The history of life on Earth can be deduced from the way that evolution has altered genes. Evolution is the change in inherited characteristics in a population from one generation to the next. Because individuals are genetically variable, in any given environment some will be better adapted and have greater reproductive success than others, which biologists describe as higher fitness. In every generation, individuals of lower fitness are lost. This is natural selection. So, over many generations, lineages accumulate genetic adaptations and new species evolve.