system
Given the following post, respond as if you're commenting on Reddit:
human
Why does sweat have so much salt?

From a biological standpoint, why is salt excreted in sweat along with water? 


From an evolutionary standpoint, why did sweat evolve to be an excretion of salt and water when potentially it could have evolved to be just an excretion of water?
gpt
From a chemical viewpoint, salt is excreted along with water because excreting water alone would increase the osmotic pressure inside the body (less water but the same concentration of salts, sugar etc. means the solutes become more concentrated), which would actually draw water back into the skin because of the concentration gradient. Evolving to excrete salt/water together means more water can be removed to allow for evaporation and thus cooling.