Why cant humans survive for more than a few days without water

Humans cannot survive for more than a few days without water because the body needs water for almost every process such as sweating, tears, and flowing of blood. Since 70% of our boy consist of water, it's the most essential fluid for living. Stay hydrated!

he forelimbs below belong to four species that descended in a direct line from the ancestral mammal shown above. of the four descendants shown, which species most likely appeared earliest in evolutionary history?