The last stadial period of active glaciation on Earth came to a close 11.7K years before present. It became evident early on in the age that this inter-stadial was different than the ones that came before it. At the start of the cycle, one of the main distinctions was the apparent lack of competition among archaic humans. As Homo Sapiens emerged into the new age, we did so unrivalled in our supremacy over the animal kingdom and possessing an unmatched mastery over the forces of nature. The cultural and technological innovation in human society at the dawn of the Holocene are by all accounts, the greatest leap forward made by any species during any other period in Earth's history. The Holocene had begun.
Anatomically modern humans at the start of the Holocene had already migrated across the globe. The shift in climate allowed humans to sustain greater populations, and begin establishing permenant settlements. Humans began organizing communities in larger groups than previously seen at key areas. These were usually areas that offered easy access to water or abundant resources. The most desireable areas also offered a strategic advantage geographically. Key areas in the Middle-East within the Fertile Crescent became central trade hubs. The Fertile Crescent offered not only a moderate climate with access to water and food, it was also a natural corridor for groups of humans migrating from Africa and a logical place to consider settling. Consequently, it grew in population and became one of the earliest examples of a true city-state during the stone age.
There were a series of advances that made the Holocene unlike any other period in history. Perhaps the most radical was the development of agriculture. This by definition was the advance that allowed the transition away from hunter-gatherer communities. While the change may intially seems somewhat trivial, it enabled groups of early humans to free themselves from the reliance on nature. Prior to agriculture, human settlements were temporary. Hunter communities often followed herd animals in their yearly migration. Gathering from nature was an unreliable means of sustenance. Providing adequate nutrition for even moderately sized groups of humans required grazing and hunting over an enormous territory. Consequently, prior to agricultre, groups of hunter-gatherers occupying a shared territory were extremely competitive and hostile toward one another. The human population only grew as much as the environment allowed.
Just as important was the development of animal husbandry in early people. In early stone age communities males in nearly every case were hunters. It was such a central occupation that coming of age ceremonies seem to have been exclusively concerned with young males stepping into the role of hunter. Nonetheless, food was scarce. Males in hunter-gatherer communities spent the vast majority of their time hunting and it still wasn't enough. Animal husbandry was revolutionary for these communities.
These two innovations seem to be the primary catalyst for the transition into the stage of humanity we refer to as "civilization". Their significance really can't be overstated - mankind effectively transcended the Darwinian arena through their discovery. For every species on Earth, their population and survival were a direct reflection of their environment. Life had always been defined by the natural world. Humanity in discovering husbandry and agriculture superceded nature. Men were no longer at the mercy of climate change or competing for the resources offered up by nature. Men became like gods - free to define nature and to define themselves for the first time.
The adoption of agriculture and husbandry didn't occur simultaneously across the globe - discovery took place many times in many different places. Human population boomed as a result. More specifically, population density increased. Large populations of settlers could now be supported in a region without much issue. In practically every community across the globe, soon after agriculture and husbandry came hierarchical social organization. Freed from the constant demands of hunting and gathering, early settlers began adopting specialization.
As the age of hunter-gatherer societies drew to an end around the world and the human population began to increase, a somewhat counter-intuitive consequence could be observed among the now isolated communities. Although their permenant settlements were often in contact with one another via-trade, they began to deviate from one another culturally and linguistically. Small groups had less reliance on trade hubs and larger villages. Regular communication lessened over time as agriculture and husbandry enabled small groups to sustain life without the need for outside support. What occurred at the beginning of the Holocene can be likened to the opposite of modern day "globalisation".
The further back in the archaeological record we look, the more similar are the symbols, icons, tools, and technologies among distant populations. Linguistically, the same effect can be observed. It's likely that Homo Sapiens in Africa possessed language. As groups migrated across the planet they may well have initially spoken the same or very similar languages. However, over the long course of time, isolated settlements each developed their own distinct dialect. By the time the last ice age had ended, populations of humans which had been isolated geographically were no longer capable of understanding one another in speech. It's clear that for most of the present age, groups of humans separated geographically have been growing further apart - becoming more different in time.
Whether or not cultural similarities are coincidental, negligible, or altogether inaccurate is the topic of heated debate among anthropologists from every discipline today. Some researchers dismiss cultural similarities outright. In their view, early civilizations emerged without any pre-existing framework to build upon. Early human progress occurred, more or less, in a regional vacuum in every case. As humans migrated and settled outside of Africa during the Pleistocene they possessed no blueprint for progress - they inherited little to no information from their ancestors in Africa or elsewhere. Around the world, human civilization began with a "blank slate". Contact between disparate human settlements was extremely limited. In this view, any similarity between isolated populations had arisen organically - asserting that progress itself has an inherent pattern of organization as it occurs in time, giving rise to the appearance of cultural overlap where none exists.
The ideological opposite to this view is less accepted in academia, but is nonetheless present. On the more conservative end of the spectrum, cultural similarities in isolated groups may be explained through shared observation. Perhaps groups of humans migrating along the same path may have encountered civilizations who shared information and offered a model, which was then put into practice once they had arrived at their destination. A more aggressive explanation is that a well organized culture existed within Africa throughout the Pleistocene. This hypothetical culture could have played an integral role in the migrations out of Africa around the world as they occurred. Things such as language, caste, religion, agriculture, animal husbandry, taboo, and astrology in this view were not local advancements made by distinct groups of humans around the world repeatedly. Instead, humans in Africa or elsewhere prior to the end of the ice age had made these advancements previously, and the information travelled with humans as they migrated into previously glaciated regions. Cultural similarity in this view occurs because most early communities were merely applying knowledge they had obtained prior to spreading out geographically.
In any case, there were apparent similarities between isolated groups. The only thing we know for sure is that if the similarities were more than coincidence, early humans failed to provide us with an explanation. On the contrary, in almost every case, a historical record of the origin of things like language, writing, or early technologies (fire, husbandry, agriculture) was veiled in mythology, providing only a cursory or somewhat misleading account. Modern anthropologists hypothesize that primitive societies were especially prone to describing poorly understood phenomenon through story telling.
As previously outlined, social organization seems to have existed deep into prehistory. Neanderthals occupied a vast territory in Europe and the Middle East for millenia. We have almost no way of knowing what the structure of their early culture was. Similarly, Homo Sapiens occupied Africa for 300,000 years before the end of the ice age. Their culture spanned the globe - including the Americas, prior to the end of the last ice age. We know for certain that these primitive cultures possesed religion, language, and art. It may well be the case that an established form of governance and social order may have been in use during the Pleistocene, having left no material evidence. What we can be certain of is that as more advanced cultures begin to appear, they organized themselves according to a strikingly similar pattern.
At every stage of social development, groups of early humans organized themselves into a roughly 3-fold hierarchical system. The castes equated to the first three "professions" or "specializations" that appeared after the most primitive hunter-gatherer stage. First, the ruler - early priest-kings were responsible for determining law, overseeing public dispute (judging), and interpretting signs (divination). Next were the warrior class. In the most primitive societies, the warrior class inherited heavily from the earlier hunter class in "hunter-gatherer" societies. Last were the tradesmen and craftsmen who produced trade goods which were often used to barter with neighboring communities.
The three-fold organization of early societies is ubiquitous throughout the planet. As population grew, the basic three tiered system was expanded to meet local needs. The ruling class was the first expand to include its own sub-hierarchy with a single king and several subordinate priests or a pupils. Many cultures over time developed a royal "court". The other castes did in time come to develop a more detailed sub-structure to suit their needs, but not to the same extent as the ruling class in the early days of civilization.