No, eating potatoes does not make human skin whiter, and it is not the reason for the existence of white people.
Skin color is determined by the amount of melanin in the skin, which is primarily determined by genetics. Melanin is produced by cells called melanocytes, and it helps protect the skin from UV radiation and other environmental stressors. People with more melanin in their skin tend to have darker skin, while people with less melanin tend to have lighter skin.
While diet can affect skin health, it does not have a significant impact on skin color. Potatoes are a nutritious food that can provide a variety of health benefits, but they do not have any properties that can lighten the skin.
The reason for the existence of white people is a complex topic that is rooted in evolutionary biology and human migration patterns. It is not related to the consumption of potatoes or any other specific food. Skin color is determined by a complex interplay of genetic and environmental factors, including UV radiation exposure, diet, and lifestyle factors.