Several species of Agave were cultivated prehistorically for food and fibre in Arizona, USA, and relict populations that remain in the landscape today can provide an insight into ancient cultivation practices. Parker et al. test whether formerly cultivated Agave parryi populations still bear a predictable genetic and morphological signature by comparing populations of uncertain origin with known wild and cultivated populations. They find less genetic and morphological variation and stronger population differentiation in populations actively cultivated in the past than in wild counterparts, and conclude that where archaeological information is lacking, the genetic signature of Agave populations can thus be used to infer their evolutionary history and to identify fruitful sites for archaeological investigation of pre-Columbian cultivation practices. The same approach can clearly be adopted for other species in similar situations.