If our blood is most like salt water how is it that we evolved to prefer fresh water for drinking?

Answer 1

Even though our blood chemistry is rich in sodium like sea water, we drink fresh water not because of taste but rather biology. Our bodies need a very fine balance of water content and sodium content. If the sodium concentration is too low, our cellular functions cease and we die. If the sodium concentration is too high, our cellular functions cease and we die.

Land animals lose water through sweat, urine, stool, as well as just by breathing. We need to replace the water that we lose or else the sodium balance will be tipped and we will die of dehydration.

Human beings are unable to drink sea water because our kidneys are not efficient enough in concentrating the urine to eliminate the excess salt and in effect will cause the sodium concentration and ultimate kill us. There are animals that have special adaptations that allow them to survive on salt water, such as more efficient kidneys, glands that secrete the excess salt from their bodies, and better methods to conserve body water... these particular creatures would likely suffer problems if they drank fresh water and die of "water poisoning" (i.e. loss of salt.)

In this case, biology has dictated taste. You can guess what happened to everyone else who didn't develop the taste for fresh water...

Answer 2

If we evolved from the sea why would the original blood water not be be salt? If we adapted to fresh water over the eons so be it, but I feel that the vestigial, beginings of salt in our blood would still be evident.

Answer 3

Dude who lied to you blood and salt water are two different things. There aint plasma in salt water

Answer 4

Too much salt causes you to retain water, it's not good for you, plus the taste of salt water is nasty :-) We take in salt through other means, we don't need to add it to our water.