Gilgamesh epic and Noah's Flood
Religions are explained their history, and origin by their gods and believers. Indeed, we cannot say who is god, where he from is, and what were the true story. There are some similarly story in different religion and country- Noah's flood by genesis, and epic of Gilgamesh by Sumerian history.
These two stories are both about flood that send from gods to destroy all mankind for man's sin and wickedness , but few amount of mankind could survive to follow hero's advice that used a big boat which made pitch.
Each story has different heroes, and little bit different description such as shape of boat, height of boat, name of hero and duration of flood etc ...
Why the meanings of story are familiar? May be upon the time there was real flood on the earth and, people talked about it-to used different version and different situation, thus the real history of flood was changed.