Genes predispose a person to be taller or shorter relative to his peers. 300 years ago certain proportion of people had the tall gene, and certain proportion had the short gene. As nutrition got better and other environmental factors promoted healthy growth, people with the tall genes remained taller relative to people with short gene. But people with both the tall and short gene are now taller than their ancestors, so the average height went up.
Whether or not any genetic evolution occurred in that process depends on whether the proportion of people in the population with the short gene also decline during the same period to contribute to the increase in average height. If so, the evolution has taken place. Short gene is being selected out of existence.
If not, and changes in height is caused by increase in average height without changes in the proportion of people with the tall and short gene, then no evolution has taken place, only response to environment. In this case, Even though genes contribute to relative height of an individual within the population, it had no role in the increase of average height.
Whether or not any genetic evolution occurred in that process depends on whether the proportion of people in the population with the short gene also decline during the same period to contribute to the increase in average height. If so, the evolution has taken place. Short gene is being selected out of existence.
If not, and changes in height is caused by increase in average height without changes in the proportion of people with the tall and short gene, then no evolution has taken place, only response to environment. In this case, Even though genes contribute to relative height of an individual within the population, it had no role in the increase of average height.
