Nearly a decade has passed since the first ancient genome of a human was sequenced. Since then, rapidly increasing numbers of such sequences have revealed the complex role of admixture in human societies and evolution. Admixture is especially evident in studies sampling a given area over the long term, such as those reported on page 1230 of this issue by Olalde et al. (1) for the Iberian Peninsula. The authors report changes in the direction of gene flow between this region and neighboring ones through time and how these changes relate to cultural history. Given that this and other studies rely upon increasing datasets, it is worth considering the balance between knowledge gained and the practicalities and ethics of destructive sampling.