Final answer:
Humans sweat to decrease body temperature; sweat evaporation from the skin cools the body, with this mechanism being more efficient in a dry environment than in high humidity.
Step-by-step explanation:
Humans sweat in order to decrease body temperature. The process of sweating involves the sweat glands increasing their output of sweat, which, when evaporates from the skin, removes some thermal energy from the body, thereby cooling it. This physiological response is crucial, especially when the body heats up due to factors like exercise or high environmental temperatures.
Additionally, for sweat to effectively cool the body, adequate water intake is essential as it replenishes the extracellular fluid lost through sweating. Sweating is notably less effective in a humid environment because the saturated air impedes the evaporation of sweat, making it difficult for the body to release excess heat. Conversely, on hot, dry days, sweat evaporates more readily, thus cooling the body more efficiently.