system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do our bodies crave salt when we need so little of it?
gpt
Because it used to be so incredibly rare to find in nature (it only occurs in small quantities in food) and we desperately need it to function. Even after we started mining salt, it was valuable until large scale industrialization in the late 1800s allowed for deeper deposits to be mined.