This chapter discusses the effect of environmental variability on human evolution. It starts with an overview of the process of evolution of hominins and covers the anatomical and behavioral differences between each genus in the human lineage. The chapter also discusses how certain anatomical traits were selected purely for the survival of the species, how natural selection can explain the way humans adapt to their environment, and how this process allowed our ancestors to respond to alterations in their environmental setting that include climate change. The chapter also offers an exposition of the different hypotheses on the association between climate change and human evolution. These include a discussion of the Habitat-Specific hypotheses and the Variability Selection hypotheses. The chapter concludes with scholarly studies that attempt to provide evidence on the coincidence of climate variability, in terms of high amplitude and high frequency, with events of human evolution in the Pliocene and the Pleistocene climate epochs.