The Paleolithic era, meaning "Old Stone Age" is a very long period of human prehistory, extending from the first tool-using homonids at least 2.6 million years ago, all the way up until the receding of continental glaciers and the development of agriculture c. 10,000 BC. Development of technology during the Paleolithic was slow, especially prior to the evolution of modern humans in eastern Africa around 250,000 years ago.

The Paleolithic era saw many early species of the genus Homo, the immediate ancestors of humans, an evolutionary line that split from chimpanzees about 6 million ago. These include Homo habilis ("handy man," 2.4 - 1.44 mya), Homo erectus ("upright man," 1.9 - 0.3 mya), Homo antecessor("pioneer man," 800,000 - 500,000 mya), Homo heidelbergensis ("Heidelberg Man," 600,000 - 250,000 yeas ago), Homo neanderthalensis ("Neanderthal Man," 250,000 to 30,000 years ago), Homo rhodesiensis ("Rhodesian Man," 300,000 - 125,000 years ago), Homo floresiensis ("Floresian Man," 100,000 - 10,000 years ago) and Homo sapiens (250,000 years ago - present).

Population densities during the Paleolithic era were low, around one human per square mile. The total population of homonids likely never exceeded one million until near the end of the Paleolithic. By the end of the Paleolithic, all species of Homo except for modern humans went extinct. The global population was likely around 5 million by this time, and the range was across every continent besides Antarctica.

The Paleolithic era was a time period of slow population expansion, migration, evolution, and the development of stone tools. The oldest prehistoric tool industry, known as the Oldowan tool industry, was used from the beginning of the Paleolithic era until around 1.4 million - 600,000 years ago. These tools consist of crude choppers, cleavers, scrapers, and awls. Only one side is worked into an edge. The Oldowan tool industry was replaced by the Acheulian tool industry over a time period of almost a million years, at different times in different places. Accheulian tools consist of distinctive oval and pear-shaped handaxes created by chopping both edges and using reworking to achieve a sharp edge.

Around 1.8 million years ago, some homonids tenatively began to colonize areas just outside Africa, such as modern-day Israel. Around 1.4 million years ago, Acheulian tool users, in the form of Homo erectus, left Africa to colonize Asia, where numerous artifacts have been found in China especially. Homo antecessor was the first member of the genus to reach Europe, which it did about 1.2 million years ago. About 250,000 years ago, modern humans evolved in Africa, and beginning around 80,000 years ago, quickly spread across Eurasia, replacing other species of Homo which came before them. By about 10,000 years ago, humans had inhabited every part of the Earth except Antarctica and a few isolated islands such as New Zealand and Hawaii.