Conveniently, the inhabitants of Earth keep very thorough, mass-produced records of their culture, society, and history, in quite an interesting format known as a "video game." After aquiring and analyzing several such video games, we have come to the following conclusions about life on Earth:
Nature
The Humans have carved out a precarious spot in their ecosystem, as nearly every wild animal found on Earth is powerful and viscious. One can scarcely leave a city without fear of being attacked by the beasts of nature.
Medicine
Human medical advances are truly astounding! There are medicinal items which will, on mere contact, revive someone on the brink of death to full health. In addition, humans have a concept of 'multiple lives' -- although not quite fully immortal, they seem to be able to die several times before their time on Earth is over.
Childhood
Children are raised quickly and without warning on Earth. They are usually cast out of their homes around the ages of 8-12 Earth years, and are instructed not to return until they have saved their town, catalogued all the world's fauna, or perhaps even saved the world from some dark menace.
Religion
The Earthlings practice predominantly some form of warrior religion. Those among them who worship gods tend to worship terribly vengeful ones, who will often grant the devotees power with which their enemies may be smitten. Others choose some form of spiritual meditation, although the goal in this meditation is to hone their fighting skills.
Sex
There are two sexes of Humans, male and female. In general, the female is quicker, smarter, more magically adept, and cleaner, while the male is stronger, more intimidating, and generally wears more clothes.
Art
All Earthling artistic skills seem to relate directly to combat, whether it takes the form of painting objects that spring to life, playing a musical instrument that invokes the powers of nature, or performing a dance which enchants their enemies.
Cultural Realms
The United States
The United States is a third-world country with a strict two-tier caste system. On the higher tier, we have the rich, exploitative businessmen/politicians, who live in extreme lushness. On the lower tier, everyone is destitute and is either a member of a gang, or a member of the upper tier's army. Once in a while, a member of the lower tier will display exceptional skill, and will be hired by the upper tier to do covert missions.
Japan
Japan is the cradle of Earth's civilization. Essentially, it is the major world power (Japanese is the world's most commonly spoken language), and the leader in technology. Other countries look up to Japan and model their government, business, and lifestyle after them, and because of that, a strong Japanese influence has permeated the entire world. All Japanese citizens are skilled in the martial arts.
Europe
Europe is a sorry and war-torn place. For most of Earth's history, it was a barbaric land, where people fought with crude weapons, and lived in gloomy stone castles that, since people could not trust even their own families, were laden with random hidden traps. At all times throughout Europe's history, every small European faction is at war with at least one other European faction.
Miscellaneous
Scattered throughout the world are other nations, such as India, Brazil, Egypt, and the Congo. Little is known about these cultures except that they are mystical and mysterious.
History
Ancient Times (4000 BC - 500 BC)
This period is sparsely documented. As far as we can tell, this is by far the golden age of planet Earth, where great civilizations flourished and left behind mysterious scrolls and orbs of wisdom. We are not sure how they were wiped out, but it was most likely by some evil cosmic forces. Precious few descendants of the Ancients lived on to later times, and were both feared and revered.
The Dark Ages (500 BC - 1700 AD)
For a long stretch of time, humans from all cultures did little more than run around, hacking things, and each other, to bits with swords. If any scientific progress was made during this age, it was slow and barely evident.
Exploration (1700 AD - 1850 AD)
Around this time, humans started to explore their world, and shift their focus from random violence to scientific and economic progress, essentially laying the groundwork for present-day society. Large improvements were made in telecommunications and transportation, and many human tasks were replaced by machines. Also around this time, the cultures began to intermingle -- not always peaceably.
World War II (1850 AD - 1997 AD)
Then, all of a sudden, they started fighting again. This time, though, scientific progress did not grind to a halt, but was instead boosted by the war effort. Grandiose war machines, insanely overpowered weapons, and cyber-bio-augmented, battle-forged humans begin to emerge in this time.
The End Times (1997 AD - 20XX AD)
Earth's current state. The previous war has, more or less, destroyed everything, leaving behind an abysmal post-industrial-apocalyptic wasteland, ruled by vile mutants and the undead.