The possibility for some other intelligent civilization having occurred on Earth earlier than we know today?

    Watching a recent documentary on this subject matter actually inspired me, since it seems an excellent logical question to ask, even if much of a history seems to exclude the idea in general, or at least simply put, why hadn't humans or some other indigenous group of hominid on Earth flourished here on this planet as an intelligent species if many necessary factors were in place allowing for such at an earlier time relative to the present day prehistoric evidence for such?  A reading on of world history (both recorded and prehistoric) would posit any number of theories, humans, for instance, were likely then the best candidates even if having at any given time also competed with other groups of intelligent enough hominids for survival.  At this humans appeared on the Earth scene, for instance, some 200,000 years ago.

Examining also Vostok petit data on climate variations in such past would have indicated that an optimum time, for human civilizations to have flourished (with a known viable intelligent civilizations candidate) would likely have been at an optimum some 125,000 years ago, and likely with a rough screwball sort of estimate a window of approximately 10,000 years to flourish, before climate change factored more heavily against the possibility of not only major agricultural centers having flourished, but providing the necessary seed for major world populace having worked technologically around climate change to sustain a given population.  Of course, there appears to be no evidence that humans exactly did flourish in significant numbers to any degree some 100,000 years ago at the last inter glacial maximum, and this would instead mean more waiting time for any potential civilization flourishing, mindful that not merely climate should be a factor here, but that any co evolutionary process would be in place allowing for the emergence of civilizations.  This means an adequate supply of potential grain sources, coupled with seasonal sufficiency and other geography permitting conditions.  How might for instance, the fertile crescent compared some 100,000 years ago relative to the present inter glacial maximum?  Might there have been fewer options, for instance, in cultivatable grasses that would yield a digestible food source, and secondly, any other condition necessary leading to the condition of human populations flourishing.  Obviously it seems mechanized labor would have a biological hybrid counter part found in animal husbandry, it seems the first cows may have originated in modern day Turkey some 10,500 year ago, with little evidence previous of any domestication of life stock prior.
    Then it seems any potential candidate for domestication, potentially may have been dispersed in some way, or neither given to the right evolutionary conditions for domestication some hundred thousand years ago potentially one might suspect, and secondly, that any domesticated livestock candidate itself might have been responsible for the co evolutionary development of grains that would be suitable for human consumption.  We know, for instance, that mammals have played an important role (not just humans alone) in the evolutionary development of the common fruiting trees, and grains likely found in agricultural production and consumption use found today.  For instance, where mammals are found in less significant numbers yields often a geography that is less suitable for mammalian habitation.  This isn't to say that the necessary factors then having occurred some hundred and twenty five thousand years ago weren't in place to aid in the development of some advanced civilization but the statistical odds may have been stacked against such development.  Thus, for instance, there might have been some agricultural development, maybe growth of small (relative to today) agricultural centers having flourished, but there may not have been a significant enough spark as it appears relative to today for any civilization to emerge and flourish in a more long lasting sense that would lead to population numbers that we see today.  Adding to this then, that we might have had additionally other competition struggles that wouldn't predominantly exist in the same ways (say another intelligent hominid, for instance, like the Neanderthal) that human populations would have been competing against for resource use.  This is also not factoring any social developments that might have taken place which aided further in the proliferation of human civilizations that we see today given through some hardening process given from a glacial minimum in so far as climate were concerned.  Of course, it seems also logical to say that human civilizations would also have had at the height of an ice age, the ability to flourish any civilization period, given that climate would likely have factored so heavily against, agricultural production, and that conditions in general were more often too harsh in the allowance of any major world wide development.  May be small population centers here and there, but often, perhaps, given by too remote for ease in inter communication, or anything would aid in the proliferation of trade and/or spreading such civilization out of a given geographic heart center.  I would be biased, as I have alluded to earlier in reasoning, that if any civilization were to emerge, it would likely emerge where the best chance could be given for things to take off.  Obviously, the modern day Fertile Crescent would likely be a good starting point...good books have been written on theorizing why this is the case.

The above map is a human migrations map.  It seems some 70 to 60 thousand years ago, for instance, when humans might have migrated out of Africa, climate change had already occurred, and likely would not have represented an optimum for the growth of an intelligent civilization.  Prior to this time frame, humans had yet to climb out of Africa, and potentially having climbed out of Africa, may have come in some transition spurt potentially.  Excepting, for instance, Native American rapid latitude advances some twenty thousand plus years ago, it would seem longitudinal advances pass more rapidly relative to one's given by latitude in so far as agricultural development?  Why might this be the case?  One because as it turns out a given plant food source would be more highly sensitized to latitude relative longitudinal changes.  If anything of civilization's growth were at stake here, latitudinal adaptations in the technological advance of plant food source seed stock would be slower in coming relative to those societies implementing hunting predation models.  Thus why Native American's would have likely had the best population success in hunting and gathering relative to adapting grains when moving from north to south.  The American bison could have been a potential candidate for livestock, but it seems also that inhibiting factors might include the fact that the behavior of the bison can be unpredictable and less likely stable in so far as a human animal inter social relation, and then the American Bison as a Eurasia relative came some two hundred thousand years ago across the Bering land bridge.  Unfortunately, it would appear the America's it would appear hadn't had an important herbivore that would aid in the co evolution of grasses, that potentially could be made use in so far as agriculture.  Maize in central America coupled too a less populace variety of candidates would pale relative to the options found, for instance, in the fertile crescent.  Thus it seems the importance in some roaming, grazing, and herding mammalian herbivore would likely have run hand in hand with the chance success, I would argue, for any intelligent human civilization, and likely the longer such herbivore has been around to graze, perhaps, the better success chance that any number of diverse grain crops would have chance in successfully evolving that could be made to some agricultural use by humans.  This is not only to say that in order likely for an intelligent civilization to arise, relies on the necessary condition that a species is intelligent enough, but all other factors of evolution work hand in hand to supply the necessary ingredients here...namely, that any civilization likely inter relates in a symbiotic way to much other biology providing aid in forming such civilization.  Livestock likely aided (prior to domestication) in the systematic development of grains that could be potentially consumed directly, as opposed to human's being reliant upon (in so far as predation models) the livestock direct as a consumed food energy source.  Without a given live stock (or some herbivore) to feed on such grasses, arguably there would be less in nature aiding in the evolution of grasses that could directly feed or supplement diets in the nutritional sense, and likely the process of having developed such grain without some intermediary biology (such as herbivore), it would be likely less possible that human's alone might have adapted a grass into a cereal crop.  Thus, if one hundred thousand years ago, humans happenstance settled into the fertile crescent region, they likely would not have had a latitudinal seed bank to rely, in adapting to such regional conditions, or if they had, the seed/grain adaptation process likely would be slower in coming relative to a longitudinal migration implementation.  Why Euro colonists, for instance, would have not only had much greater technological vantage, but also had longitudinal favorability in their advance across the Atlantic.  If they were forced more North and South, in terms of migration, they would have likely had a slower time/progress in settling and adapting grains to a given geography, and thus why, for instance, euro colonization at times has favored self similar geographic latitude ranges in terms of agricultural production.  Early human ancestor migrants, as we might suspect, may have been more hunter and gathering types, but even if they had the ability to cultivate some grains, adoption to cultivate in this manner, may have been supplementary in nature, as opposed to predominant.  While I have seen physicist suggest that bio mechanically meat is the great source of human intelligence, it is not the favorable choice of intelligent civilizations having emerged.  Why so?  As it turns out the production to energy harvest expense is often greater when an intermediary biology is necessary for consumption.  Thus, for instance, it typically cost more for to produce ounce for ounce for the same caloric energy, a pound of meat relative to the same amount of energy in grain.  As it turns out, this added energy cost, is often given by the expense of raising both the grain/grasses, and the live stock together as opposed to direct to consumption models of grain alone.  Likely then I would posit statistically the best chance for an intelligent biology not only comes from the ability of its adaptation to found sources, but that it may be rarer for instance, finding intelligent civilizations that exclusively feed from heterotrophs alone and neither has some independent direct to consumption model for autotroph food energy source.  Secondly, consuming plant sources (autotrophs) for energy gains through organized social cultivation, would mean that human civilization were better slated to withstand seasonal variations in food sources, found either in traditional hunter gather and/or smaller subsistence based farming models.  This would mean humans could dispense with and evolve, sexual cycles that were no longer seasonal in nature, and to say the least a greater expanse in many respects of human intelligence could be utilized.  For instance, humans could then expend more energy on thought abstraction as opposed to relating everyday experience and inquiry through survival necessities more often than not. 

     If it were true that some intelligent civilization had emerged and humans were likely it in so far as such biology responsible for flourishing.  It would seem if populations were abundant then as they are today.  Likely we might have as in the claim of proof, evidence or indicators of such.  Likely in such civilization, one should imagine, technologies and materials being created that should arguably with stand all the elements of time, that something could be more oxidation or corrosion resistant, for instance, might be a tell tale sign that a civilization once highly advanced had existed.  Even if it were some hundred thousand years, and happenstance, human ingenuity as the spark of major fireworks managed to kindle together a massive global civilization.  It appears statistically speaking we managed to do this on time scales ranging in the tens of thousands of years, and climate cycles could at least provide some window.  On the other hand, if such were the case, nothing of clear evidence has emerged at all, and likely then it seems much more far fetched, given that humans had to advance themselves well throughout the globe firstly which might have been a greater pre occupation relative to settlements and/or all the process hurdles of technological adoptions and adaptations that would be necessary relative to what might also have been a presumably slow advance out of Africa.  Now consider the advance of Native Americans throughout the America's in a mere wink of twenty thousand years which covered far more latitudinal turf than our early ancestors well over a hundred thousand years ago, and one might sense that technology even then for the hunter gathering just weren't even the same relative to more modern hunter gatherers.  It seems more likely in mind, that our ancestors of a hundred thousand years before likely hadn't the same bank of knowledge to rely upon in so far as technological adaptation and adoption that could likely have been important precursors for technological advancement and the creation of agrarian civilizations which in turn produce the types of advanced civilizations that we see today.  The slow northward advance of human's migration out of Africa seem to fit in line in another way with human societies potentially here, if it were that conditions were either too harsh or too easy, social communication and travel would appear geographically more limited, more often than not, this legacy still persists to this day in certain sub tropical if not tropical regions of the world.  However, it seems something of the more ancient ancestor may have had something of a fastidious and geographically fixed mindset (relatively so) to the more modern invading colonist.  While intelligence may have been there, change and technological adoption and adaptation necessities were likely differed potentially in so far as cultures.  Furthermore populations being limited and less likely dispersed should necessarily limit growth expansion.  It is one thing to walk into another world that is more extreme relative to one's own, and have to learn how to live all over again.  Whereas the north to south advance of a hardened and likely well knowledge banked culture of another peoples, could mean much greater advantage in such migration as in the Native American migrations case, especially where essentially migration is rooted in such culture by stronger demands of necessity.  Today's civilization is very marked in a strongly global way.  At least it is un mistakable that if our civilization ever did perish, there could likely be found evidence throughout the world of such civilization having existed, and that much of the technology and sciences attributed to the systematic development of infrastructure were neither owing to a stricter geographic locality in so far as technological achievement, and while there, for instance, are indicators and evidence for more broad and widespread communication of ideas, art, and knowledge in a given region, one could not also mistakenly notice that at times regional locality and restriction that disseminated knowledge might have flowed in travelling from one region to another.  Thus the world for classical antiquity might have seemed to be restricted to a region around the Mediterranean at times, even if had included parts of Asia Minor and beyond this.  Obviously, it would seem that statistically one were harder pressed to find that technological achievements of an isolated output or agricultural center while significant for its time should have some major comparison with the achievements of today.  That is, likely to produce, for instance, the body of expertise, both in terms of metallurgy, for instance, geology, chemistry, and any number of involved sciences that would lead to some like kind exotic materials production.  Is likely owing to some civilization that should have some broader population expanse.  At least this is another bias that one might have in terms of a civilization's achievement potential, and if something alien were to produce much the same, likely that this disseminated knowledge were the collective efforts of a greater populace of individuals in an intelligent society that provided significant valuation in such developments, and weren't merely happenstance the accidental achievements of a handful of extraordinary geniuses alone, and also given by the power of civilization to divest into diverse economic systems that lead to a greater array of occupational trades.  Considering that while our civilization harnesses in a broadly global sense the energy systems of our own planet, if ever the resources, for instance, of this civilization were able to harness the power and energy likely of a given solar system, one might, for instance, expect a population of expanse in reflection to the achievement potential of such as a rule.  Thus, such civilization might be able to travel more readily freely, and inexpensively to any local neighbor in the solar system, as opposed to present day travel models which suggest quite cumbersome economic costs relative to the size and scale of a present day civilization, for instance.  

I have heard at times theories about migrants from say, for instance, regions of the Mediterranean all the way to North America, even so predating Viking chronicles, and while if these accounts were nothing more than myth or at worst some manner of hoax, on the other hand, one might likely refrain in the belief that anglo civilization would have had reason to thrive and flourish if it had come at some time frame earlier than that given either by the Vikings or by European colonists.  One at least given the range and scope of an economy, not withstanding the differences of sea man ship that could be accounted for in a given Atlantic passage crossing.  It seems if ever any from classical antiquity might have arrived, the economy from which such voyagers had come could be much differed relative to later coming European colonist, and likely for all the many voyages and expeditions that were granted by then, were given likely by the numbers increasing odds for survival.  Early colonist's did have extremely difficult times, for instance, even when supplies should be given to some frequency.  On the other hand, if the Roman's had yet to completely consolidate Europe (into the British Isles), or at that the northern now German frontier were anything of another world at the apex of an ancient civilization past, its hard to imagine ancient Egypt or Mesopotamia, heavily investing itself so much further when frontiers were its doorsteps all around, and at times, if the stability of a given system were not as likely in as much through the perpetuation of wars or anything other that were costly to such civilization which likely should drain resources away from exploration alone.  It seems less likely also to proclaim something more of what seems mysterious to us, if only ignorance should exist in so far as the deductive reasoning and evidence of the likely power that any past civilization might have harnessed, and here then I imagine only the possibility that nothing more than a small fleet of ships possibly might have by some remote chance landed on American shores, but likely could have been well less at sea owing to some navigational mistake which landed a fleet for all one should know in the Sargasso sea.  If ever such crew might never have returned home from any American soil that it landed upon, after all nothing of documentation exists suggesting such account for all we know, and then one lone Irish monk that managed a crossing from one end to the other, did so on much rarer accounts.  Hardly a hand few of individuals, despite any romantic inclination, having survived with much chance alone, other than having been overwhelmed by indigenous populations likely.  At this one imagines, death or assimilation, but certainly not having brought the pyramids of Giza to the central America's.  More so, syncretism, is merely happenstance to the notion that mounds pyramids alike resemble ideal geometries of a intelligent like minded humans that emerged from the thick of the ice, and had with this in mind all the similarity in fashioning similar social hierarchy, and at this resorting in a similar fit, monument building as an expression of social, religious, political, and economic ideals.  Civilizations such as these come flourish, wane and find re expression.  As architectural engineering changes accordingly and diversifies, it seems the era of megalith and extreme monument building also changes, but this emerges as civilizations themselves have only proliferated greater knowledge and that expression in form has changed relative the past.   In as much that civilizations past, may have preoccupied themselves by scale and divested its resources to much greater extent expressing with purpose the symbolism of power found by scale.  The tenure of an intelligent civilization may have found the diversity of its cultures having urged restraint, sobriety.  Emperors, kings, and pharaohs could less argue over time, that they hadn't squandered the resources of an empire when they had done so on some ruthless war that might have left the power of any legacy in question.  The gods themselves might have been questioned if not given by fractious social division between war gods and those of peace.  While others could be declared heretics and have their name defaced from walls.  Thus architectural scale itself might have been left in some meaningless void to some owing to the rise of a more cynical populace of people in well tenured civilization that were given to much freer reign of thought than ever before.  Imagining that some other intelligent human or hominid might have arisen before, if this were ever possible, on the other hand, one sees potentially a similar chord of history having arisen in the imaginations of such intelligence.  Having gone through some similar maturing process which would lead to some similar synthesis in thinking and development...maybe some much more rapid than others, but a lot given to the statistical hardships of time, and that progress is not linear.  Anything of social evolution could rapidly devolve for any number of reasons.    

  What have I not covered so far in terms ideas in terms of the future of, for instance, Earth in so far as human civilization?  In speaking, for instance, of human civilization's present relative to a given past, it seems not only that one may speak of a world that is even more globalized in terms of communication, and language in general, the evidence of this is given by decline in the diversities of languages in general, but also that language that once may have been more limited in terms of its reach in written form (by way of complexities), has been met by the synthesis of a broader reach into a given larger population set.  I argue that this synthesis could be described in ways lending to uniformity neither having existed so much prior when, for instance, the scope of trade broadens and makes for greater demands in reaching a broader populace.  Thus ancient scripts, for instance, may have transformed into easier written character type forms, or to say the least, no longer a reed and stylus found in the common practice of such writing in so far as adapting, for instance, fewer character variations, and that this would in turn lead to accessibility provided by new writing medias.  The hallmark of progressing civilizations might be, for instance, described by evolution of written languages which in turn are given to furthered character sets relative to a given language ancestor (ironically) although I am not certain this is always the case.  If anything of human intelligence ranges in the power of the social evolution of language, this could be owing to the range and scope of human memory which according to more broad population sets accord ease in aids to memory and the usage of such written language.   In re echoing previous ideas, the transformation of culture might also be described by the power and change provided by education and literacy as a civilization has advanced.  If in some ways, technological advancement could be hallmarked by the nature of homogenizing aspects of communication in a given world.  On the other hand, it seems also that another diversity itself has arisen, as suggested earlier, leading to the changes and transformations given to a civilization of people in so far as social inter relations are concerned, how such people see themselves in relation to their governments as one might theorize influencing the degree by which governments initiate in varying ways, for instance, anything of investment into infrastructure, and how people in such civilization might be led.  For instance, why is it harder for modern civilizations, to embrace their leaders in ways that might have been found more commonly in the ancient world?  Why, for instance, had the role of leadership declined in so far as the practice of commonly linking such to a Earthly spiritual realm?  In part I have, as others, have suggested a reason for this, and in another way, one might possibly find greater links to the power of science, education, and reason similarly transforming a given culture, no less that reason and passed wisdom from one generation to the next, leads to a change in thinking when it is understood that something of recorded history echoes into a then present.  Not that the progress of civilization is always met by anything linear always in nature or growth even in the natural sense by way of exponential foundations but that seemingly at times regression has also occurred.  New resentments of old cultural foundations, for instance, may lead to new iconoclasm, and with it at times the ransacking and parting of old knowledge which later have been rekindled through periods of enlightenment and renaissance.  I would theorize in like kind that there are likely other worlds having experienced potentially a similarity in some manner in terms of its own history.   As to a given future world, our own civilization may find itself in the perils of self existence and annihilation, as likely continued proliferation of ideas make potentially abundant designs for both progress and self destruction.  Even more so with population growth, comes the perils to our own modern concepts of individuality and freedom but also providing even greater opportunity one might expect.  The perils it would seem may be something of increasing demand for conformity and cultural uniformity, while on the other hand, in the model of freedom, increases in education more broadly impacting a given populace is met by only increased diversity with respect to the spheres of occupation to be had.  It seems the coexistence between the noise of democracy and an erosion of this seem to be ever so at times in a given struggle.  In this day and age, for instance, if world governments haven't similarly embraced the notions of democracy, on the other hand, finding much reason of suspicion in it.  I leave open the question of what remains here to be seen, although certainly I hope that achievements of progress here are met only in furthered advance of democracy.  Submitting to a bias here, marking to a cornerstone to the concept of 'democracy', when our civilization is willing to embrace different ideas, we maybe more willing to critically reason through our own sets of notions.  The more self similar we are in relation to other, also risks the ability of civilizations to change or progress.

Much of opinion here is in reference to "Guns, Germs, and Steel" by Jared Diamond, Carl Sagan, and others.