Final answer:
The conservation of salt, dark skin, and dark eye color are evolutionary adaptations to a tropical climate, providing protection against UV radiation and preventing salt depletion.
Step-by-step explanation:
The conservation of salt, dark skin, and dark eye color are evolutionary adaptations to a tropical climate. In regions with high UV radiation, such as tropical areas, dark skin pigmentation is favoured as it provides protection against the harmful effects of the sun's rays. The presence of melanin, which causes the darkening of skin and eyes, helps to absorb ultraviolet light, protecting cells from DNA damage, and reduces the risk of skin cancers. It also serves to prevent the breakdown of folic acid, which is crucial for cell division and growth.
Furthermore, in such environments, the conservation of salt is vital due to the potential for sweating and depleting the body's salt stores in the heat. These adaptations have evolved over time to enable humans to survive and thrive in tropical climates.