It's not entirely accurate to say that only traits controlled by genes are acted upon by natural selection. While genes are the primary mechanism for inheritance and therefore the main source of variation that natural selection acts on, there are other factors at play:

1. Gene-Environment Interactions:

- While genes provide the blueprint, the environment plays a crucial role in shaping how those genes are expressed.

- For example, someone with genes predisposing them to be tall might not reach their full potential height due to malnutrition.

- Natural selection can act on these phenotypic differences, even if the underlying genetic basis isn't the sole driver.

2. Epigenetics:

- Epigenetics refers to changes in gene expression that are not caused by changes in the underlying DNA sequence.

- These changes can be influenced by environmental factors and can be passed down to offspring.

- Natural selection can therefore act on these epigenetic modifications, impacting the survival and reproduction of individuals.

3. Acquired Characteristics:

- While Lamarck's theory of inheritance of acquired characteristics is largely discredited, there's evidence of some transgenerational inheritance of acquired traits, particularly in the context of stress responses.

- This, however, is a relatively minor component compared to genetic inheritance and is debated within the scientific community.

In summary:

* Natural selection primarily acts on variation in traits that are inherited, and genes are the most important source of such variation.

* However, the interplay between genes and environment, along with epigenetic modifications, also influence the traits that are subject to natural selection.

* Acquired characteristics play a very limited, if any, role in shaping the course of evolution through natural selection.