Final answer:
Skin tone changes from birth to adulthood due to factors like melanin production, which can be influenced by sun exposure and health conditions. Evolutionary adaptations have also contributed to variations in skin pigmentation based on geographical location.
Step-by-step explanation:
The change in skin tone from birth to later years can be attributed to several factors, one of which includes the body's production of melanin. Right after birth, a newborn's skin can be covered with vernix and may have patches of peeling skin. As the child grows, skin tone can change due to environmental factors such as exposure to sunlight, which increases melanin synthesis. It typically requires about 10 days after initial sun exposure for melanin synthesis to peak. The skin tone can also be affected by various health conditions, like liver disease or Addison's disease, which can alter the appearance of skin pigmentation. Moreover, evolutionary changes in pigmentation have occurred in humans over generations, often in relation to geographical location and sun exposure, affecting vitamin D absorption and protection against UV radiation.