But the key word in near-analogue turned out to be "near". The planet's biosphere almost completely lacks potassium. A diet lacking in potassium causes decreased intelligence in humans, which can be permanent if it is not remedied quickly—especially if this occurs during childhood. If one is denied it for too long, death always results (though in reality, potassium deficiency is more likely to result in death before mental retardation). The reason for this lack is thus: potassium is as lethal to Destiny life as arsenic is to Earth life, and eons earlier, a form of sea life evolved the ability to concentrate potassium as a defense against predation. However, when sea life dies, its remains are deposited on the ocean floor. Ultimately, most of the element was thus leached out of the planet's ecosystem, concentrating it there. After that, volcanic activity was the only process that reintroduced potassium into the ecosystem.