Similar to wild populations, traditional landraces (varieties, cultivars) of many annual crops form dynamic populations, the genetic make-up of which changes over time. This point was clarified in our earlier discussion (Chapter 5, and see Chapters 8, 9) on the changing incidence of early and late bloomers responding to seasonal rainfall among both wild populations and cultivated plants. Usually, traditional farmers would preserve sowing materials from the last yield of traditional cultivars (see Glossary, Botany, Ecology and Agronomy, Traditional cultivar (landrace)), which comprise a sample of sorts of the entire yield. The population make that farmers thus own reflects the historical evolution that occurred in their fields. This includes natural selection originating in pressures caused by agents such as pest and disease epidemics, extreme climate, frequently occurring random mutations and the farmers’ own selection processes when choosing the plants or plots in their fields from which seeds will be cached for the next season. Since traditional landraces are dynamic, it would be unreasonable to assume that all of the differences found between the progenitors of the founder crops and the domesticated types are solely the result of the pristine domestication episode. In other words, some of the differences between these two plant groups are the results of selection processes that took place during the thousands of years that have elapsed since domestication and under (a cultivation regime) domestication.