This chapter discusses the Age of Human Survival—which occurred tens of thousands of years ago during the Pleistocene Epoch. The first few early humans struggling to exist then were rather sparsely distributed and had little aggregate impact on the use component of resources. Our ancestors exploited easily accessible natural resources in order to gain a toehold in an environment that was harsh and threatening to this new species. Small groups of hunter-gatherers eked out a tenuous existence in highly variable environments and climates. The human relationship to resources during Era I can be understood by reference to individual decision theory. A fundamental principle of economics is that individuals maximize their own welfare. With the assumption that individuals were rational decision makers who chose actions regarding resources with the aim of furthering individual interests, the limited resources during Era I meant that individual decisions revolved around basic human survival.