Recent revelations suggest humans hunted animals as endurance hunters, running pretty into the ground by way of our superior cooling ability.
But we lose significant salt through sweat. One random Google page suggests you might sweat 1,000mg per hour.
Yet supposedly prehistoric diets were extremely low in salt, in the range of 650mg/day and no major dietary source seems to exist aside from rock salt or sea salt, which hunter gatherer Man did not have.
How did early Man get enough salt to fuel endurance hunting in the heat?
I would like to extend this question towards neolithic inland dwellers and paleo/mesolithic general population.
Given the amount of salt we are consuming today, it's hard to imagine how and inland people would be able to get "enough" salt even without excessive sweating. Mining of salt is known to have occured from the bronce age (at Hallstatt, Hallein, Dürnberg), but what about several thousand neolithic years before?
The people with the smallest salt intake I know of are amazonian aboriginals. Whereever it rains, salt is whashed away, no surface salt is to be expected therefore.
How did they do it?
You should post (or crosspost) this to /r/AskAnthropology or /r/AskScience — it is about pre-history and anthropological theory, not history (which generally deals with written records). There are some experts on here who deal with paleoanthropology but I suspect you'll get better responses from the other subs.