Hmmm, living off of the land is the key phrase here, so if all of the land were back to wild land with native plants and animals, both of which were abundant, your land might support one human to every 10 square km, or aprox. 25,000 people. If fishing is good, twice that amount maybe. Poor fishing, game and wild plant availability will greatly decrease the population, just as it would the wild creatures and boom times would increase the population. Add agriculture and the number goes up considerably and would only be affected by drought, but then you're right back to where you are today with a mega population and limited land mass to properly support them.