Skin tone is primarily determined by which of the following factors?

Skin tone is primarily determined by the amount of melanin present in the skin. Melanin is a pigment that is produced by specialized skin cells called melanocytes. The primary function of melanin is to provide protection against harmful ultraviolet (UV) radiation from the sun. Individuals with higher levels of melanin tend to have darker skin tones, which offers better protection against UV damage. Conversely, those with lower levels of melanin typically have lighter skin tones.

While other factors such as environmental exposure can influence factors like skin health or tanning, the baseline skin tone itself is fundamentally based on the genetic and biological production of melanin. Thus, the amount of melanin is the key determinant when considering what primarily affects an individual's skin tone.