Tens of thousands of light-years from our Earth, a race of sentient mammalian bipeds became the dominant life form on an Earth-like planet named Kobol. These mammalian bipeds were indistinguishable from the humans of Earth right down to the cellular level. Their DNA was even compatible...they were actually human - the result of an astonishing parallel evolution of human beings on both Kobol and Earth.
The humans of Kobol achieved dominion of their world long before the humans of our Earth even developed language. Eventually the people of Kobol developed a civilization with all the amenities of an advanced society (e.g. automobiles, television, advanced medicine, etc.). They even created artificial life forms such as sentient machines. Known as "Cylons", these artificial life forms served as a slave caste. At some point, they rose up and waged war against their masters.
Eventually, the war so devastated Kobol that both humans and Cylons fled the planet. Using a space-folding drive that enables space ships to make instantaneous "jumps" across vast distances in space, the humans went on to colonize twelve separate worlds in a single star system, becoming the "Twelve Colonies of Kobol". Simultaneously the Cylons colonized a planet they named "Earth" (the first planet to bear that name). On this Earth, a race of biologically-reproductive organic humanoid Cylons became the dominant species and they enslaved mechanical Cylons.
Eventually, history repeated itself and the mechanical Cylons rose up and waged war against the organic cybernetic life forms that were their masters. During this war, a unique type of Cylon that had progressed to the point where it was able to exist as virtual 'software' on a higher plane of existence observed the conflict. Because this entity existed on another plane, it had a non-linear perception of our space-time continuum, allowing it to see future events. A benevolent being, this virtual Cylon Entity created other virtual beings to serve as its messengers. Some of these messengers came to view the Cylon Entity as a "God." However it did not like to be called by that title. The messengers appeared to five humanoid Cylon researchers and warned them of the impending destruction of their planet's population. After a nuclear conflagration that did indeed destroy the planet's population, the only survivors were the five researchers. They survived by re-inventing a technology from Kobol called "organic memory transfer." This technology "resurrects" a Cylon upon their body's destruction by saving their consciousness and then "downloading" it into an identical clone body.
These Final Five surviving humanoid Cylons realized that the humans of the Twelve Colonies would continue to create artificial life. So they headed for the Colonies to tell the humans to treat their creations well and keep them close. Because their people hadn't developed jump drives, the Five's ship traveled at relativistic, but subluminal speed. Time slowed down for them, but thousands of years would pass before they finally reached the Colonies. Along the way, they stopped at the Temple of Hopes, a temple that was created by their ancestors where they prayed and got a sign that led them to their "Earth."
The humans on the Twelve Colonies initially lost most elements of civilization from Kobol after they settled on the twelve worlds. However, Kobol-evolved humans possess a capacity for genetic memory. This genetic memory does not take the form of passing on personal memories, but the passing on of an unconscious knowledge of certain invented concepts and ideas such as technology, language, engineering and even fashion and music along with various other aesthetic cultural aspects.
Over a period of a couple thousand years, all the technological and cultural aspects from Kobol completely reconstituted because the genetic memory of these concepts and ideas 'leaked' into the subconscious minds of various people who gradually and collectively reinvented these aspects of Kobol society. Eventually, even the genetic memory of the concept of artificial life in the form of Cylons was reconstituted in the conscious minds of such men as Daniel Graystone and Tomas Vergis.
Eventually these new Cylons were used as slave labor within the Twelve Colonies. As had happened before, they eventually rose up and waged war against their masters. By the time the Final Five humanoid Cylons arrived at the Colonies, the humans had been fighting the Cylon Centurions for over twelve years. The Centurions were already trying to make flesh bodies. They had created the "Hybrid," but nothing that lived on its own. Remaining a secret to the people of the Twelve Colonies, the Five offered the Centurion Cylons a deal: if the Centurions agreed to end the war with humanity, the Five would create organic humanoid Cylons for them. The reason the Five were so willing to create new humanoid Cylons was that the Centurions had developed a belief in a single loving God. One of the Five, Ellen Tigh, believed it changed everything; if the Cylons embraced love and mercy, then the cycle of violence could end. The Centurions agreed to the deal. With the reason being kept secret from the Colonials, the Cylons agreed to an armistice with them and left the system.
The Five and the Centurions then withdrew to a planetoid-sized mobile space station called "The Colony" placed beyond the Armistice Line. The Five then developed eight humanoid model Cylons, which were designed upon their own physiology. They created "Number One" first and named him John, after the father of Ellen Tigh. He was also made in the image of Ellen's father. John helped the Five build the other seven humanoid models. Ellen was close to Number Seven, Daniel, and John, out of jealousy, contaminated the amniotic fluid in which the Daniel copies were maturing and then corrupted the genetic formula. This wiped out the copies permanently.
John rejected mercy. He had a twisted idea of morality, so he turned on the Five. He trapped them in a compartment and then he took the oxygen offline. John boxed the Five at first but ultimately unboxed them and downloaded them into new bodies, but he blocked their true memories and implanted false ones and introduced them one by one into the colonies. He introduced Saul Tigh first, not long after the Cylon War ended. Several years later, he introduced Ellen Tigh. Over the years, he gradually introduced Galen Tyrol, Samuel Anders, and finally Tory Foster. Cavil put the Five into the human population in order to truly show them what humans are like. He hoped that when they died and resurrected (which would restore their real memories) they'd be ready to admit they were wrong.
John erased all knowledge of the Five's identities from the minds of the other surviving active humanoid Cylon models. Although the other six knew about the existence of the "Final Five", they did not know their story, what they looked like, and were even programmed to never speak of the Five or search for their identities. Only the Number One models knew the truth of the Final Five; a fact unknown to the other six models.
Adopting the name "Cavil", the Number Ones still wanted justice for the enslavement of the Centurion Cylons and convinced the other Cylon models to the same thinking. During their forty years of isolation, the seven active humanoid Cylon models never stopped hating humanity. For them, the war never ended. It had simply evolved as they had evolved.
During this time, the humanoid Cylons created more "Hybrids" to pilot their basestars. The Cylon Entity would communicate with these Hybrids. It even communicated with the First Hybrid as well. Realizing the impending destruction of the population of the Twelve Colonies, the Cylon Entity also chose a young girl named Kara Thrace to serve a special purpose. She would one day bring the survivors of the Twelve Colonies to our Earth, which the Cylon Entity had found some time ago.
After the attack on and destruction of the population of the Twelve Colonies of Kobol, a virtual being messenger of the Cylon Entity appeared to Dr. Gaius Baltar. Appearing in the form of a Number Six model humanoid Cylon, she would appear to him on a daily basis for the next several years and influence him towards events that inevitably would lead the remnant human Colonial population towards our Earth.
Over the next few years, the Cylon Entity would give several people visions and send virtual being messengers to appear to several others, such as a Number Six model humanoid Cylon named "Caprica." The virtual being that would appear to her appeared in the form of Dr. Baltar. The Cylon Entity would also give a Number Three model humanoid Cylon partial visions of the Final Five in between resurrections. Eventually, it gave her a full vision of the Five while she was at the Temple of Hopes (by then it was known as the "Temple of Five").
Sometime after this, a virtual being messenger appeared to Kara Thrace in the form of the Number Two model humanoid Cylon known as "Leoben Conoy" and then the Cylon Entity transported Thrace and her Viper to the Cylon-colonized "Earth" in a process that visually looked as if Thrace and her Viper had been destroyed. Upon arriving on that Earth, Thrace's Viper crashed landed, killing her. However, the Cylon Entity possessed a very enhanced form of resurrection technology that could even be used to resurrect a human. It was able to immediately save her consciousness and then download it into a perfectly replicated body. It then placed the resurrected Kara Thrace in a newly-built replica of her Viper and sent her back to the battlestar Galactica and the remnant human Colonial fleet with slightly altered memories of her voyage to the Cylon-colonized Earth. It also placed the jump coordinates to our Earth within her subconscious and the jump coordinates to the Cylon-colonized Earth within the navigational computer of the replicated Viper. Several minutes before she was returned to the Fleet, the Cylon Entity used a musical tune to make the four members of the Final Five who were within the Fleet aware of their nature as humanoid Cylons. The Cylon Entity would also later use this musical tune as a way to bestow upon the human-Cylon hybrid Hera Agathon the jump coordinates to our Earth.
Eventually, the Cylon Entity subconsciously made the four of the Final Five within the fleet aware of the jump coordinates within the replicated Viper and it was used by the Fleet and a rebel Cylon basestar to lead them to the Cylon-colonized Earth. Arriving on the planet, they discovered the ruins of the destroyed Cylon civilization. Several months later, the circumstances of a battle led Kara Thrace to finally bring the Galactica to our Earth. Upon discovering that human beings had also evolved on this Earth, the people of the Fleet gave the planet the name "Earth" and decided to settle and cast aside their technology to join with the pre-verbal tribal human population. The surviving humanoid Cylons also decided to join with the Colonial humans in the settlement of our Earth and gave their basestar to the survivng Centurions so that the Centurions can be free to find their own destiny. Soon after the settlement began, the Cylon Entity made Kara Thrace a virtual being. She joined the Cylon Entity and the other virtual beings on the higher plane of existence.
The survivors of the Twelve Colonies and the remaining humanoid Cylons went on to interbreed with the native Earth-evolved human population. Hera Agathon would have so many descendants that they would go on to breed with people all across the entire world and eventually every person on Earth would be a direct descendant of Hera Agathon, meaning the entirety of humanity became partially of humanoid Cylon heritage.
As the Kobol-evolved human Colonials and the remaining humanoid Cylons interbred with Earth-evolved humans, the genetic memory capacity was diluted and became latent. It took more than 140,000 years before it became active again. After the end of the Stone Age, the capacity began to reemerge and certain ideas and concepts reemerged. However, they reappeared only in rudimentary, fragmented and even modified forms. For example, the Colonial religion gradually reconstituted in the minds of the people of ancient Greece - but in a modified form (e.g. the "Lords of Kobol" became the "Gods of Olympus). The monotheistic religion of the Cylons (and a minority of Colonial humans who follow monotheism like the followers of the Monad Church) would later form the basis of the Abrahamic religions of Judaism, Christianity and Islam. These three Abrahamic religions would play an important role in Earth's history and culture (with Christianity and Judaism eclipsing the reconstituted Colonial religion of the Ancient Greeks and Romans in Europe) and still continue to shape it well into the early 21st century.
Over a period of several millennia, a multitude of Colonial ideas, concepts, and cultural aspects reemerged because of genetic memory. Although they would continue to reemerge in rudimentary, modified and fragmented forms, eventually these fragments coalesced into complete reconstitution of Colonial aspects. For instance, the Colonial language eventually reconstituted as the "English" language. The English language did not suddenly appear, but instead evolved through centuries of modifications along with amalgamations from numerous other languages. It was all the result of the genetic memory of the language 'leaking' into the subconscious minds of people who unconsciously directed the language toward a linguistic endpoint that is an exact replication of the Colonial language (apart from a certain profanity word). Other languages from the Twelve Colonies would reappear and reconstitute themselves among the human population of Earth over several millenia. One example is the Greek language (both ancient and modern dialects), which is a reconstituted version of the Tauron language. Another example is the Romanian language, which is a reconstituted version of the Gemenese language.
As a result of genetic memory, by the early 21st century virtually every cultural aspect of Colonial society has reemerged: language, names, fashion, engineering, architecture, furniture, music, art, cuisine, household appliances, television, automobiles, federalized government, judicial systems, labor unions, military protocols, firearms, computers etc. In addition, the humans of Earth have been making the first steps into exploring outer space with the development and rise of manned space exploration by the Soviet Union (and its successor state, the Russian Federation), the United States of America and most recently, the People's Republic China; since the later half of the 20th century and the early 21st century (something their Colonial human and humanoid Cylon ancestors did 150,000 years before their arrival on Earth). Countries such as the United States, the United Kingdom, Canada, Australia and New Zealand collectively form a near perfect replication of Colonal society more than 150,000 years ago – just without advanced technology such as FTL jump drives and sentient machines...yet.