Enoch and long life spans in Genesis

Enoch was of interest to many people of days past for the same reasons that he has peaked your interest.  A number of pseudographical works were attributed to him.  I even read somewhere that someone was proposing the idea that Enoch was taken away by space aliens in a UFO.  I don’t know how much, if any, of this I buy into but it certainly makes for interesting speculation.  I have oftentimes wondered if he ever really existed and if so, what really happened to him.

Whenever I see the extremely long life spans attributed to the folks in Genesis recall the Sumerian King Lists.  There are such strong ties with Judaism and the civilizations of Mesopotamia I speculate that it may have been a literary devise, attributing immense age to characters from the story which was meant give authority and lend familiarity to the finished texts.  Perhaps it was just part of the ritual of storytelling from the time, much like we sometimes start a storey with “once upon a time”.  

I don’t have the figures handy but I wonder if both the Sumerian and Hebrew texts ascribe greater life spans to the antediluvian characters than to the postdiluvian ones?
And, if so does this means anything?