The plants that we have today underwent a process of natural selection through the actions of people long ago. People would, for example, pick berries. They would select the largest ones and the ones that tasted best. After they ate those berries, they would excrete the seeds. They might also spill some of the berries or throw away fruit that was too ripe when they got it home. Many of these berries would sprout near their homes. Those sprouts would all have come from the seeds of the biggest and best berries and so their fruit would tend to be larger and better on average. After years and years of this process, the berries near the people's homes would get larger and tastier. In this way, they were naturally selected to be larger and better tasting.