In the Evolution Narrative we've been exploring, our population is asexual - they don't require another of the species to reproduce. This occurs in animals as well (parthenogenesis). And mutation is not the only contributor to variation in these species.
An asexual lizard species has been found to double its chromosomes during meiosis. Meiosis is the cell division that results in reproductive cells. Crossover events and mutations can occur, increasing variation depending on which split sets come together.