This paper seeks to understand why hunter-gatherer settlements become less dense as their populations increase, as opposed to the tendency of sedentary settlements to become denser with increasing population. They propose that settlement density is dependent on mitigating proximity costs at low settlement sizes, and movement costs at larger settlement sizes, and that these proximity costs act strongly upon hunter-gatherer groups, as they do not have the social structures or material technologies to alleviate them, thereby creating less dense settlements. The authors construct a model based upon this theory, and then test it using a cross-cultural database of 1,760 hunter-gatherer camps from 112 different cultural groups. They find that hunter-gatherer groups become less dense as settlement size increases, but as movement costs become more important than proximity costs, the rate at which they become less dense diminishes. They also find that settlements begin to become denser when there is food security and proximity costs are mitigated, indicating that domestic food production is not necessarily requisite for settlement densification and that densification may have emerged in tandem with the advent of agriculture, as opposed to as a result of it.