Once upon a time in our observable universe existed millions of galaxies, each galaxy contained thousands/millions of solar systems, stars and black holes but there happened to exist a particular galaxy out of the millions of galaxies with the name "the milky way", of which there also existed a point - compared to the size of the entire galaxy (milky way). By magnifying this point, one would find a solar system and in that solar system existed planets (about 8 now), but there seemed to be only one planet amongst these planets and possibly in the entire observable universe where life existed and it's none other than where we exist "planet Earth". Considering the vastness of our observable universe, the inhabitants of Earth refused to believe that they were alone and then the quest for their cosmic neighbours (Extraterrestrials) began.
Well up until now we still are not sure if we are alone or not, what we have are theories/speculations about the possible existence of extraterrestrials. There are so many of them but we would look at some few.
Religion and gods
The Christian bible which is sometimes regarded as one of the oldest books on Earth is made up of many different ancient texts/books, written by different authors and is believed by Christians to have been inspired by the Jewish/Hebrew god "Jehovah". This book contains ancient religious and moral practices and of recent, it has been discovered that the book underwent tremendous changes throughout history, which some claim was due to political reasons. One such change was the removal of some books like the "book of Enoch", in fact some of the texts contained in the book of Enoch are also contained in the old testament of the Christian bible, examples are the case of the fallen Angels, the fallen Angels having intercourse with human females and they begat giants sometimes called "The Nephilims". However in the book of Enoch, these Angels are also referred to as"The watchers".
The bible is believed to be of Hebrew origin but surprisingly there exists another ancient texts which some scholars believe the Hebrew bible got inspiration from, because of their similarities, this ancient texts are referred to as the "ancient Sumarian texts" and it originates from Mesopotamia. In this ancient texts the watchers/Angels are mentioned but this time around with the name "Anunnaki", these Anunnakis were worshipped as gods/deities most especially by the Mesopotamians, also the great flood mentioned in the old testament of the Christian bible is mentioned in this ancient Sumarian texts.
However, because these beings (Anunnaki/watchers) and similar events appeared in these separate religions and in some other religions too, some other scholars think this couldn't have been a coincidence but as a result of humans first contact with extraterrestrials (aliens), in fact the general conclusion was that religion itself began as a result of man's first contact with extraterrestrials, probably because they were very powerful beings and they were also Giants - reason why they begat giants when they had intercourse with humans. According to one ancient astronaut theory, these aliens came to earth in search of gold and might not have had intercourse with humans but instead hybridized themselves (combined their DNA) with the homo erectus - an ancient ancestral specie of humans, through in vitro fertilization, the hybridization resulted in the existence of homo sapiens (modern man). The homo sapiens were used as slaves to mine the gold.
Also, according to these scholars, this theory explains why we are so attracted to gold, why man suddenly transitioned from hunting and gathering to what we now call agriculture - domesticating and breeding plants and animals, how we knew how to use weapons, e.t.c, and in fact, some archeologists claimed to have found fossilised bones of giants in southern Africa - where gold is located. It is also believed that these aliens were responsible for some of the monumental structures found on Earth - like the Pyramids, which they believe the ancient humans couldn't have done on their own. To further blow our minds, it's now known as fact that civilization originally began in Mesopotamia, but that doesn't mean the theories are well established facts, as a matter of fact the science involved in the discoveries and theories discussed earlier is considered pseudoscience by mainstream science.
UFOs ( Unidentified Flying Objects)
As far back as the fourth century AD, there has been reports of unexplainable flying objects in the sky, these objects are normally attributed by people to belong to extraterrestrials, probably because of their weird behavior and structure. These UFOs are often depicted as flying saucers, like those found in movies and used by aliens to invade earth and abduct humans.
Well according to recent reports from Pentagon in the United States and based on their investigations, these strange flying objects might not be of extraterrestrial origins.
In 1961, an astronomer named Frank Drake devised an equation that can be used to predict the existence of advanced civilization within our galaxy - milky way. Astronomers have discovered thousands of exoplanetary systems similar to our solar system with some containing earth-like planets and according to the Drake equation, taking the properties of these exoplanetary systems as factors in the equation, yields high civilization possibilities yet physical observation gives a null result - no signs of advanced civilization. The contradiction between the prediction of the Drake equation and physical observation raised a paradox, now referred to as the Fermi Paradox - named after the notable Italian-American physicist and Nobel laureate Enrico Fermi , according to this paradox, where is everybody ?
Different proposals have been raised to resolve the Fermi paradox - mostly why we are unable to make contact with extraterrestrials, you can find them here.
In addition to the above theories, there have also been claims of a particular alien sightings, most especially in the United States, this alien is called the "Grey alien" see here for more details.
Still wondering why alien related issues mostly occurs in the United States.
what if we are all getting things wrong ?
Aliens are commonly depicted as very powerful beings in terms of very advanced technologies compared to ours, with weird looks - big heads, large eyes, e.t.c, and always like to invade/colonise lesser civilized life forms like we on Earth. The idea of aliens being very powerful beings in terms of technology originates from the fact that there exits exoplanetary systems far older than our solar system and that if life forms like us exists, they must have gone very far in terms of science and technological advancements. But what if we are looking at the whole alien stuff from the wrong direction ?, What if we are the first life forms to exist in our observable universe?
With the way things are going, it's most likely possible that we would eventually inhabit most planets in our observable universe, in fact we have already started, like in the case of planet Mars. Top billionaires like Elon Musk, Jeff Bezos, e.t.c are already owning private space shuttles, just in case planet Mars becomes ready for living things to inhabit. Even though it might not take place soon, it would eventually happen, probably thousands/millions of years later, by that time we would have advanced our technologies to make it happen. From what I can observe and extrapolate, history is probably repeating itself and we might eventually become the aliens we are already picturing now, as I explain below.
Millions of years ago, man originated in Africa and belonged to the specie called Ardipithecus (There are fossil records of this specie), this specie went through series of evolutionary changes until it eventually became a Homo specie. Some of this Homo species migrated to other parts of the world, the reason for the migration is still a matter of scientific debate. These Homo species that migrated to other parts of the world further underwent evolutionary changes (skin color, nose size, eye color, e.t.c) due to the environment they found themselves. In addition to the physiological and morphological changes was their advancement in their way of life which was as a result of improvement in their sciences and technologies - it was originally done to better adapt to their environments.
It seemed those that remained in Africa felt Africa was too comfortable (after all it was conducive enough for man to originate) and so did not make too much progress in advancing their sciences and technologies. Thousands of years later after the migration, Africa became colonized by the Europeans - migrated people that later became more technologically advanced.
If you can read meaning into what I'm trying to get at, then you would realise why I previously said history might probably be repeating itself and that we would eventually become the aliens that we are currently picturing. Some of us might think because we exist in a computer/information age, informations about the missions to move to other planets would be available for our future generations and therefore could help in preventing the future catastrophe, but most of you my friends are not aware of the so called Elites - few very powerful people that can turn the world around. Due to political reasons these informations we think would be available could be wiped out of history/existence by the Elites, when this happens, either we go to invade/colonize those in other planets or they come to invade/colonize us without being aware of our true origins.
Probably in another nearest future, there would be galactic wars (not world wars) for universal power and so will these events continue to happen till only the universe/cosmic mind knows what next would happen.
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Lastly, please don't forget to do the needful
If you enjoyed my jargons.