The State of Nature is a device used by political scientists to describe the state of mankind before civilisation and governments were established. John Locke, for example, described the State of Nature as an essentially peaceful time with abundant resources. Thomas Hobbes, on the other hand, declared it a time of war of "every man against every man" in which life was "solitary, poor, nasty, brutish and short."
Locke and Hobbes had different notions as to why establishing a central government was important: Locke wanted government to ensure individual rights to "life, liberty and property" whereas Hobbes preferred a central authority to keep men in awe, so they would honour their contracts and commitments.
But my use of the term "State of Nature" does not refer to governments. Instead, it describes the period of time 1.8 million to 10,000 years ago (the so-called Pleistocene era) when man finally evolved from apes and proto-humans.
The State of Nature was not a single moment or generation, however, but a duration of many thousands of years. Mankind evolved in a changing environment, and so we have different scenarios manifest in our genes for each of those times. During the ice ages, we evolved a body type and mental disposition for that environment. During times of prolonged war and upheaval, we evolved traits for those times. During times of peace, we evolved for that as well.
Evolution is a process by which an organism's genetic qualities are continually matched against the environment. Those who survive, especially those with advantageous genetic mutations (which occur from time to time) are deemed most fit in the environment. They are able to have the most offspring and promote their family line.
As a society, we are constantly repeating the different States of Nature. Our ancestors killed nearly all of the Indians, and relished doing it. We now repudiate our ancestors, and cannot imagine why they were so brutal. But in truth, we are the same people, simply in a different State of Nature. The States of Nature roll over us, working like a periodic engine of change.
Individuals don't evolve by themselves. Society does, as a collective beast. Society has evolved many different stable distributions of traits across people for the various scenarios from the State of Nature. Different people serve different roles. Some are born as leaders, as shown by their desire to lead a hierarchy of men, without being cowed by the disapproving glances of rivals. Some become labourers, because they desire approval from great leaders, and are not motivated to compete for power.
But mankind retains in its collective genome the different possible societal configurations from the State of Nature. A stable social state, with its tuned distribution of traits, can return quickly if the ambient environment so warrants.