It was a mission of such intent that led to the creation of modern man. At some point between 400,000 years ago and the second interglacial period in the Middle Pleistocene (around 250,000 years ago) the trend in cranial expansion and the elaboration of stone tool technologies developed, providing evidence for a transition from Homo erectus (meaning "upright man") to Homo sapiens (meaning "wise man"); this origin/transition is speculated by human scientists as either due to a uni-regional development that spread (which seems likely, due to the general genetic homogeneity of Homo sapiens sapiens) or multi-regional developments that merged.
"Humanity" in the Marvel Universe, once established as Homo sapiens sapiens, developed much as it did in the real world, generally ignorant of its genetic relatives the Eternals and Deviants, and even of the few isolated cases of mutation (with the earliest recorded being the Homo sapiens superior En Sabar Nur, known as "Apocalypse", in 3,000 B.C.) to, on the whole, develop identical cultures to those of the real world, parallel in almost every way; at least until World War II in 1939, when the appearance of superbeings became public, proliferated, and unavoidable.
Changes between human cultures in the Marvel Universe and the real world since that point have entirely reflected the greater presences of superbeings, notably Homo sapiens superior ("Mutants"), although in recent times all metahumans have been targeted by certain bodies; this can be seen in such governmental legislations as the weakly-backed Mutant Registration Act, and the current, popular Super-Hero Registration Act, and traditional prejudices against mutants and certain other superbeings.
The number of so-called "mutants" within humanity as a whole has risen dramatically, and fallen almost as dramatically, since the first recorded appearance of a known mutant, 5,000 years earlier, with the birth of En Sabah Nur, later known as Apocalypse. Apocalypse was a lone mutant, but almost 5,000 years later, by the 1970s, there were hundreds. Due to unknown causes, the mutant population exploded within the following decades, seeing perhaps 32 million worldwide by the 1990s (the evil Cassandra Nova exterminated 16 million with her Sentinel attacks, and that was theorized to be approximately half of the mutant population). Finally, in the Decimation event of 2005, Wanda Maximoff's alteration of reality removed the powers of most of the remaining 16 million, leaving perhaps a few hundred remaining mutants on the Earth.
The circumstances and opinions surrounding mutants as a political body have always been very much polarized, presumably because of a similar polarization within the attitudes of the mutant community; some strove for acceptance, whilst others declared themselves "humanity's successors" and sought to take their place by force. As a result, opinions on how to deal with the mutant community have always been similarly divided. There have been attempts to exterminate mutants (with the robotic Sentinels, or the deadly Legacy Virus, amongst other things), enslave them (using the mutate process created by the Sugar Man and employed by the Genegineer of Genosha), or indeed both (such as the Weapon Plus Program), and even appease them (such as when Magneto was given sovereign command of the country of Genosha); it has only been recently that mutants have been accepted as members of society by law, as equal to other superhumans (as evidenced by the Super-Hero Registration Act, which affects all with metahuman abilities, regardless of origin of said abilities).
However, as a side note, given the events of the series Son of M in which the depowered mutant Quicksilver restored the powers of other "fallen" mutants in the wake of the Decimation event, it seems likely that the mutant X-Gene, the presence of which denotes a being as Homo sapiens superior rather than Homo sapiens sapiens, either leaves a "genetic shadow" within the rest of the individual's DNA, or takes its characteristics from said DNA. However, it is more likely that both assertions are correct.
This can be stated due to evidence witnessed; the traditionally Inhuman-controlled Terrigenesis (the taking of the mutagenic Terrigen Mist) was a process designed to induce benevolent mutations to maximize the genetic potential of the individual, creating unique powers. Now, given that applying Terrigenesis to a former mutant restores powers of a similar nature to their own, it can be seen that the general genetics of an individual seem to give some shape as to which powers they will manifest (the ultimate genetic fingerprint); however, since the powers are restored at far greater level than they existed before, it seems likely that the DNA sequence of a mutant, even a former mutant, contains far more inherent power than that of a human (and almost certainly more than most Inhumans).
The actual Atlantis sunk in the "Great Cataclysm" event some 20,000 years prior to the current era, with those who would become Atlanteans first remaking it as their home approximately 2,000 years later. A largely peaceable existence has been their lot since then, at least as far as confrontation with surface-dwellers was concerned, at least until the 20th century, which saw hostile interactions between surface-dwellers and Atlanteans, whether between the groups as a whole, or when the Atlanteans sided with the Allied Powers in World War II. However, the Atlanteans are currently at peace with the surface.
What is known is that these marine humans known as "Atlanteans" have now reached the extension of the land dwelling Homo sapiens similarity; the genetic distinctions are at their ultimate point, meaning that genetic disconnection between the two forms is almost complete, meaning they have become two different species. This can be witnessed by the fact that all known pure Atlantean/Human hybrids (Namor, Namora, Namorita) are infertile.
As a race, the average Atlantean is far more powerful than the average "human" – they stand capable of speeds of swimming up to 30 mph, breathe perfectly underwater (although cannot survive on the surface for more than 5 minutes), have a life-span of approximately 150 years, and are far more physically durable and strong than the average human, as a side effect of living in such a high-pressure environment.
Additionally, there are an offshoot of Atlanteans known as Lemurians; they are typically distinguished by their greener skin and reptilian appearance, although their powers remain identical to their Atlantean counterparts.
However, the experiment was abandoned for unknown reasons, and the Inhumans created a society of their own. Powers were induced by the powerful mutagenic chemical known as the Terrigen Mist, although this exposure created lasting genetic damage, and physical aberrations, amongst the Inhumans. As a protective measure, a prohibitive eugenics program was instituted, to minimize the impact of such damage. Now, bound by strict caste structures and breeding laws, only suitable Inhumans are allowed access to the Terrigen Mist. Additionally, power level after Terrigenesis dictates one's place in society.
As suggested, the power levels and appearances of Inhumans vary greatly, from the insignificant to the awesome, much as mutants. Recently, it has been revealed that Terrigenesis is not exclusive to the Inhumans, but can be applied to former mutants, their powers removed in the Decimation event. However the former mutants powers return as twisted, uncontrollable versions of their previous powers.
A civil war destroyed the unity of these beings, in their first generation. A difference in ideologies saw the Eternals Kronos and Uranos pit their followers against each other, with Kronos' army prevailing, driving Uranos and his followers from Earth. This is particularly relevant to the genetics of the Eternals' ancestors, since much changed after this schism.
Uranos and his exiles found a Kree supply store on Uranus, hoping to come back to Earth and retake it by force using parts to create a vessel for themselves. Several stayed behind to form their own colony, but this was ill fated, and wiped out before the 20th Century.
Uranos and his followers were attacked by the Kree before reaching Earth, with one member taken for vivisection (the analysis revealed a terrestrial origin, which prompted the Kree to begin the experiments which would lead to the Inhumans), leaving the remaining party to limp to Saturn's moon Titan, forming a colony there.
On Earth, Kronos pursued experiments into cosmic energies; however, one of these experiments would have results quite different than expected. Exploding in his face, Kronos was atomized, his energies becoming the Titan God of Time, whilst all other Earth Eternals were doused in fallout radiation; these radiations altered the genetics of all Eternals they touched, activating their latent abilities, and ensuring that all born to the Earth Eternals would have similarly activated genes and levels of power.
It was this which created the second schism of the Eternals; in the first Uni-Mind, it was decided that Kronos' son Zuras would succeed him. However, in order to avoid dissension, the other son, Alars, left, arriving on Titan. There, he encountered Sui-San, the last of the Titan Eternals, and the two repopulated Titan; however, the new Titan Eternals were less powerful than their Earth counterparts, since Sui-San had none of the augmented genetics possessed by all Earth Eternals.
Earth Eternals have astonishing power derived from channeling cosmic energies, capable of using this power for such varied feats as matter rearrangement, energy blasts, flight, super-strength, virtual invulnerability and an almost infinite lifespan. Titan Eternals are, on the whole, endowed with similar powers to lesser levels, although the individual Thanos has surpassed all Eternals in power; his powers were already greater than any Eternal of Titan, and have been augmented with technology and mystic energies, not to mention a great increase in power attached to his resurrection at the hands of Mistress Death.
Ghaur, a priestlord among the Deviants on Earth, claimed they were created by a single Celestial called Tiamut, or "The Dreaming Celestial", and by doing so he did a crime among the Celestials and was punished.
The ugliness and deformities as standard within the Deviant race, coupled with the beauty of their foes, the Eternals, have led to a societal structure which abhors physical beauty, to the point of killing those deemed too beautiful.
However, the Deviants were masters of science, having perfected cloning and other genetic manipulation tools whilst mainstream humanity were still living in caves; this was demonstrated by the beast Spore, an unstoppable creature capable of assimilating the genetic codes of any creature assimilated into its mass.