Cultural practices alter the environments that then select on people, so a population partly builds the conditions it is subsequently shaped by.
Dairying is the standard case: herding created a milk supply, which made lactase persistence advantageous, which made dairying more valuable. The selection pressure was manufactured by the behaviour it then favoured. The general point is that human environments are substantially artefacts, so adaptation is to a target the population is still moving.
In practice
- A firm that automates a process creates the skill shortage that makes further automation attractive.
- A city built for cars becomes a place where not having a car is unworkable.