The most famous of all mythological creations starts off with the sentence in the Old Testament, Genesis 1:1: "In the beginning God created the heaven and the earth." Now maybe we invented the concept of creations in order to give our gods something to actually do. Unfortunately, say in the case of God and Genesis that peters out after just six days! Now what? Anyway, back to Genesis 1:1.
Now I don't know who actually wrote Genesis 1:1, it certainly wasn't a supernatural all-powerful, all-knowing, deity. Whoever it was however possessed knowledge that you wouldn't assume upon reflection to have been knowable or even suspected way back then. Now that someone who wrote Genesis 1:1 had no right to know these things, that heaven (the sky and beyond) and Earth were created, yet they did know these things. Now that suggests that somebody else who knew these things, informed the Genesis 1:1 author. If you believe in time travel, perhaps we of the 21st century (or later) who know better, travelled back in time and told him (or her), though that's unlikely in the extreme. That someone else probably wasn't terrestrial.
Now every cultural mythology has a creation story or stories, and that shouldn't be the case based on first hand human observation. If you are going to propose an "in the beginning" scenario it should be based on your personal observations and understandings of the natural world as you view it, or on historical records. So something is slightly funny here since presumably it's the same humans who shouldn't suspect any such thing as creation that in fact wrote all those creation mythologies! And these creations are all unique one-off creations. God only gave 'birth' to Adam and Eve (or humanity) once. So, it's unique (one-off) creation mythologies, like Genesis 1:1 that are puzzling, not creations per say, like say the birth of your cat. A birth, a dawn, etc. maybe a creation of sorts, but it's not a unique creation. It's not a one-off Big Bang "In the beginning", beginning.
Could you, in your day-to-day observations of the heavens and the earth (or life the Universe and everything) assume anything other than both heaven and earth have always existed? The heavens are that which exists above our heads; the earth that which exists below our feet. Since there's no human who has ever lived who can't attribute knowledge of the heavens above and the earth below; that can't verify any animal or plant species popping into existence in their time and place, what need for creation? Perhaps Genesis 1:1 should have been written "From the infinite beginnings God just enjoyed overseeing the eternal heavens and earth and directing the events that unfolded on them." To our historical ancestors, that actually should have made more sense.
It's often easier, as in the above invented quotation, to accept something has always been and always will be than to try to explain how it came to be in the first place, especially if it is not all that obvious that it (whatever you're interested in) ever needed to come to be in the first place.
Whatever you are interested in comes in standard forms. There are various creations in mythology that are fairly universal.
Creation of the Universe is a case in point; those stationary points of lights in the night sky - the stars. Now the fact that the patterns in the night sky don't alter from your birth to your death, and haven't altered from historical records, suggest something unchanging, and therefore without need of a beginning or a creation.
Creation of the heavens involves those moving points of lights in the night sky - the Sun, Moon and planets. The problem here is that they endlessly repeat; move around and around in circles. In fact, if you consider a circle, or an ellipse, where is its starting point?
Creation of the Earth is a universal myth, yet equally universal is the fact that there is no human record or observation anywhere, anytime, that Terra Firma didn't exist.
Creation and separation of the land, the sea and the sky is another near universal tale, yet the same objection holds - all personal observations and historical records note and log all three, so why not assume the separate land/sea/sky interface has always been?
Creation of your territory or nation is another case in point. The Japanese have a mythology that accounts for the creation of Japan, yet no humans were around when Japan was 'created' by various natural geological forces.
Creation of life is another part of the Genesis creation story, but one hardly unique to the Old Testament. You may have had a sequence of pets, say cats. Individual cats are born, and they die, but the concept of cats collectively goes back and back and back as early as the earliest of human records. So, why is there a need for God (or any other deity or natural process for that matter) to create cats? Haven't cats always existed?
Creation of humans by God (or in other cultures the gods) is also puzzling since there was never a time when, in historical records, it is recorded that a human being (who could be verified as an actual historical figure) was aware that they were the first human being and therefore human beings were created.
The need for mythology isn't all that difficult to explain but creation mythology is difficult to explain since eyewitness testimony suggests that how things are is how they always have been. At the heart of this mystery is the concept of infinity. You have a personal beginning and an ending, but you can't really conceive of THE BEGINNING or THE END. That's because of that nagging question that always pops up, "well what came before that" and "what happens after that" - cause and effect; endlessly; cause and effect. It's not difficult to keep extrapolating back and back and back in time without running out of 'back'. It's not difficult to keep extrapolating forward and forward and forward in time without running out of 'forward'.
INFINITY: Your personal observations require things to be ongoing in a linear sense (no beginning; no end) or cyclic (round and round she goes, where she stops, nobody knows) - there's no alpha, no first cause, and no omega, no last effect - but there is ever ongoing causality in all things.
A sort of combination of the two infinities, birth - death, is that most fundamental of all observations, and it repeats and repeats and repeats. Any individual birth - death is linear and unique; but on the larger scale a birth gives rise to a death, but before that death there's another birth and the wheels just go around and around - different players; same scenario. So what need is there to propose a first birth; a first creation?
LINEAR INFINITY: From a past infinity, eventually arose your great, great grandparents; great grandparents; grandparents, parents, children; children's children; children's, children's children to a future infinity. No beginning, therefore no creation. Or, in the opening words of the TV show "Ben Casey": "Man; Woman; Birth: Death: Infinity".
CYCLIC INFINITY: Seasons are cyclic; sunrise/sunset ditto; phases of the Moon are also cyclic; the planets go round and round. No circle has a beginning, therefore no creation need apply.
Among the other great terrestrial cycles, not all obvious within a human lifespan or sometimes not obvious without scientific analysis, we have the rock cycle (compression - erosion); the water cycle (evaporation - precipitation); the carbon cycle (carbon dioxide - carbon + oxygen); the nitrogen cycle; and others as well.
CAUSALITY INFINITY: Cause and effect; everyday in every way you observe cause and effect. A cause is in turn the effect of a previous cause. An effect in turn causes something else to happen. So the words 'cause' and 'effect' are synonymous. Again, there cannot have been a first cause, nor a final effect.
If every record you consult, from your own memory to the memories of your elders to your elders' elders to all written and pictorial records, and you note, without exception, in that they all record that lions roam the plains of Africa, then you must assume that Africa always existed and that lions always roamed and did so on the plains of Africa. You have no evidence to the contrary. What logical reason do you have for assuming that wasn't always the case? So, what need for a creation mythology that creates lions, creates their roaming around abilities, and creates the plains and Africa for them to roam in? There's no pressing or obvious need to speculate that "in the beginning" a deity created Africa, the African plains for the deity's lions to roam in.
The solution is that while you can't come up with plausible creation stories, modern science can. Modern cosmology now tells of the 'in the beginning' Big Bang event. Darwin and palaeontologists tell us that once upon a time there were no lions, and geologists say that way back then there was no uniquely African continent, and climatologists note that there were no plains in Africa. Alas, creation mythologies predate modern science by thousands of years so we're back to square one. The answer lies elsewhere, but again still with those more knowledgeable than us. Those more knowledgeable, all those thousands of years ago were the 'gods', or IMHO advanced (modern scientists and then some) aliens. ET tells us about "in the beginnings" having boldly gone where our modern terrestrial scientists are only now just treading.
Now these 'gods' often take credit for some of those creations they had bugger-all to do with (like God of the Old Testament as related in the Book of Genesis). In many cases the creation tales are muddied because ancient humans, who ultimately were the scribes who penned down these stories as told by ET, couldn't, for example comprehend a Big Bang cosmology but could deal with a golden cosmic egg that hatched. Modern genetics was so much mumbo-jumbo but creating a woman out of a male rib, while mysterious, was in their ballpark of comprehension. Modern geology and plate tectonics would have been double-dutch to the ancient Japanese, but it made perfect sense for the original pair of their gods to stir the oceans with a spear and the salts that crystallised out at the tip became the first of the many Japanese islands, all created by their gods.
In summary: Could you, all by yourself, based on your lifelong observations, come up with a requirement that the Sun and Moon needed a creator? Or that the stars in the sky weren't really infinitely eternal but needed a creator? Or, those members of your own kind, human beings, weren't always around, and forever shall be around? There is nothing you observe, or that any of your ancestors observed, that could in any way lead you to postulate, identify and accept any ultimate "in the beginning(s)". If that's the case, then my 'ancient astronaut' ET scenario is an alternative and viable hypothesis.
Further reading:
Van Over, Raymond; Sun Songs: Creation Myths from Around the World; Mentor, New York; 1980.