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The saltiest sea on the planet is the Dead Sea. It is 10 times saltier than the ocean average (34 g in the ocean to 340 g per liter of water in the Dead Sea). This high salinity is because it has just one main inflow, the small Jordan River, has no outflows, and is in a place with a very hot (meaning high evaporation) and dry climate.

How would the human digestive and urinary systems need to be changed in order to be able to filter salt water and drink it safely, and at the same time store water like a camel does in the desert?

Note: Among their adaptations to dry conditions, camels produce extremely concentrated urine and extremely dry feces.

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    $\begingroup$ For one thing, water must be stored somewhere... that's what those camel humps are for. That means a hump on the back. The longer the needed storage, the bigger the hump, the more it will compromise the flexibility of the spine. $\endgroup$
    – JBH
    Commented Dec 6, 2020 at 15:26
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    $\begingroup$ It is not at all necessary to store the reserves of fat and water on the back, be original, why not place it in a more traditional, for humanoid, image in the form of a belly or simple subcutaneous fat? $\endgroup$
    – French Thompson
    Commented Dec 6, 2020 at 16:10
  • $\begingroup$ You could, but you'd look like Fat Albert and it would conflict with too many joins and internal organs. It's out of the way on camels for a reason. If you take the weight of the camel less the humps and compare it to the weight of an average adult human, then multiply that ratio by the weight of the humps alone, you'd have a good idea of how much weight you're adding to your human. $\endgroup$
    – JBH
    Commented Dec 6, 2020 at 16:12
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    $\begingroup$ @JBH and yet humans still function when they are so obese that they carry around double the suggested "healthy" body mass. So it is still a valid option. It's not as if the hump weighs as much as the entire rest of the camel. $\endgroup$
    – Gwyn
    Commented Dec 6, 2020 at 16:32
  • $\begingroup$ Anyway, remember that when it comes to water retention, the camel's respiratory system, especially the nose, is the game changer, rather than the hump, which is mainly for storing fuel in the form of fat for when there's nothing to eat. $\endgroup$
    – Gwyn
    Commented Dec 6, 2020 at 16:36

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Salt Glands (alternatively, hyper-efficient kidneys)

This is how animals IRL drink salt water and manage to not die. This is how saltwater crocodiles, sea turtles, seabirds, and the extinct mihirungs dealt with excess salt. That said, salt glands are pretty much unknown in mammals. This may not be because "they can't do it", but rather because they may not need to, mammalian kidneys are quite a bit more complex than reptilian or avian kidneys and may be able to perform the roles of salt excretion without the need for specialized salt glands. The loops of Henle in kangaroo rat kidneys are crazy long and allow them to extract all the water they need just from eating seeds.

In fact, wild Bactrian camels (but not domestic ones, for whatever reason) are capable of drinking saltwater with no ill effects. It's unclear if such adaptations are present in wider desert-dwelling mammals. Marine mammals are known to not need to drink fresh water but they supposedly get all the fresh water they need from the bodies of their fish prey. How marine herbivores like dugongs meet their water needs is unclear.

Also, camels do not store water in their humps. They store fat. Camels meet their water needs by having incredibly efficient kidneys, complex nasal turbinates, and other adaptations that allow them to reduce the amount of water they expel to very low amounts. But they still lose water over time, and eventually do have to drink, they cannot get all of their water from their food like kangaroo rats.

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  • $\begingroup$ this answer is quite perfect, $\endgroup$
    – Dexyan
    Commented Jan 15, 2021 at 12:37
  • $\begingroup$ Could you tell us more about how these adaptations ( modifications) work? $\endgroup$
    – French Thompson
    Commented Jan 22, 2021 at 15:48

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