True.... the third human on this planet came from the first two..
-OR- a bodacious Yarn must be invented.. to explain him or her.. usually involving the first two.. Removing the first two is an act of circular logic.. or changing the subject to confuse or obfuscate the issue..
Prima facie evidence demands that at one time there was a/the third human on this planet.. thereby proving the first two.. The established Yarns prove that humans love a good story.. and that science fiction requires a logical tale, reality never needs to be logical at all.. Reality needs not make any sense at all to humans..
Could be that Exodus(Torah) ch. 1-3 might be metaphorical with much deeper meanings to a long story/history where origination could be merely minutia.. to a broader story with more scope..
Yes it is a myth. I can see that I am making progress : )