Life requires balance. We balance work and family. We eat a balanced breakfast, sometimes. And we balance our electrolytes. That salt-water synergy is not just key to our health, but to our very existence. Because the appearance of molecules that maintain our fluid balance coincide with the evolution of multicellular life. The findings appear in the journal Physiological Genomics. [Romain A. Studer et al., "Evolution of the epithelial sodium channel and the sodium pump as limiting factors of aldosterone action on sodium transport"]

When it comes to osmolarity, single cells keep it simple. They adjust their fluid intake by importing or exporting salts across their membranes. But once a creature is multicellular, things are more complex. Many cells don’t have direct access to the environment, so a complex system of hormones and sodium channels and pumps has to manage the movement of salts, cell by cell, to keep the whole body hydrated.

To trace the evolution of this regulatory system, scientists searched the genomes of organisms that represent the major branches of life’s tree. And they found that two proteins—a sodium channel and part of a sodium pump—arose slightly before the first multicellular animals. Which strongly implies that the ability to regulate electrolytes is a big reason we’re here. As any scientists worth their salt will tell you.

—Karen Hopkin

[The above text is a transcript of this podcast.]