Why do human beings need to drink so much water when our closest relatives (gorillas, chimps, and bonobos) drink very little?

Answer 1

Humans have very active sweat glands. Our sweat glands causes us to lose a lot of water through the evaporation of sweat. Although all primates have sweat glands, the human sweat gland is highly responsive to heat. Which means, we tend to sweat a lot in the presence of heat whereas other primates don't. although they sweat, gorillas do not sweat as much as humans. Gorilla will pant to keep cool. Moreover, when it's very cold, you might notice that you have to use the bathroom more. That is because, you no longer need a high amount of water to cool you down through perspiration.

https://academic.oup.com/icb/article-pdf/12/1/109/6053983/12-1-109.pdf