Hunting and gathering was humanity's first and most successful adaptation, occupying at least 90 percent of human history. Following the invention of agriculture, hunter-gatherers who did not change have been displaced or conquered by farming or pastoralist groups in most parts of the world.
Only a few contemporary societies are classified as hunter-gatherers, and many supplement their foraging activity with horticulture or keeping animals.
In the 1970s, Lewis Binford suggested that early humans were obtaining food via scavenging, not hunting. Early humans in the Lower Paleolithic lived in forests and woodlands, which allowed them to collect seafood, eggs, nuts, and fruits besides scavenging. Rather than killing large animals for meat, according to this view, they used carcasses of such animals that had either been killed by predators or that had died of natural causes. Archaeological and genetic data suggest that the source populations of Paleolithic hunter-gatherers survived in sparsely wooded areas and dispersed through areas of high primary productivity while avoiding dense forest cover.
According to the endurance running hypothesis, long-distance running as in persistence hunting, a method still practiced by some hunter-gatherer groups in modern times, was likely the driving evolutionary force leading to the evolution of certain human characteristics. This hypothesis does not necessarily contradict the scavenging hypothesis: both subsistence strategies could have been in use – sequentially, alternating or even simultaneously.
Hunting and gathering was presumably the subsistence strategy employed by human societies beginning some 1.8 million years ago, by Homo erectus, and from its appearance some 0.2 million years ago by Homo sapiens. Prehistoric hunter-gatherers lived in groups that consisted of several families resulting in a size of a few dozen people. It remained the only mode of subsistence until the end of the Mesolithic period some 10,000 years ago, and after this was replaced only gradually with the spread of the Neolithic Revolution.