Why can't humans drink sea water?
Water is essential for human life, but since more than 96% of the liquids on earth are seawater, there is very little fresh water suitable for human hydration. However, considering that there are mammals such as dolphins and whales that live in the sea, and that there is a
Why can't we drink saltwater? | Live Science
https://www.livescience.com/32454-why-cant-we-drink-saltwater.html
The reason why humans cannot drink seawater is simple: seawater is too salty and causes kidney dysfunction. Rob DeSalle, curator at the American Museum of Natural History in New York, told Live Science: 'Most animals use their kidneys to remove impurities from the water. Drinking seawater removes the salt that must be excreted from the body. You end up taking a lot of it. '
The kidney is an organ that plays an important role in producing urine from excess water and waste products in the blood and excreting it from the body. However, while the kidneys cannot make urine, which is more salty than blood, seawater contains more than three times as much salt as human blood. Therefore, Live Science points out that in order for humans to get rid of excess salt after drinking seawater, they must drink more than the same amount of fresh water as they drink.
On the other hand, creatures living in the sea are adapted to the environment where fresh water cannot be drunk by various means. For example, seabirds such as albatrosses, seabirds, and penguins that live in the sea for a long period of time have special secretory glands called salt glands that take out salt and discharge it from the nose before the water they drink reaches the stomach. There are also marine mammals such as whales and dolphins that are hydrated from food to prevent salt.
Regarding these creatures, Desar said, 'Marine mammals have special enzymes and cellular structures to excrete excess salt from the body. They have super kidneys.'
Then, the reason why terrestrial animals like humans do not have 'super kidneys' is that animals that are ancestors of terrestrial animals have evolved to drink fresh water in order to advance from the ancient sea to land. .. Animals, including primate ancestors, need to adapt to the terrestrial environment, where there is abundant freshwater such as lakes and rivers, but little saltwater, in order to spread the print from the seaside to the inland. did.
At the end, Mr. Dessar said, 'Most of our ancestors, whether ordinary animals, primates, or insectivora, are no longer exposed to salt water, so these animals are naturally eliminated. By specializing in the ability to treat salt-free water, drinking salt water has become extremely dangerous and harmful. '
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