And all the days of Methuselah were nine hundred sixty and nine years: and he died. (ASV)
He is mentioned in Genesis as the son of Enoch and the father of Lamech. His name has become a general synonym for any living creature of great age. A close reading of the dates in the Old Testament reveals that Methuselah is said to have died the year of the Great Flood. According to fundamentalists who read the biblical accounts literally, the reason for the longevity of Methusaleh and other figures in the first several chapters of Genesis is that a protective layer covered the Earth and filtered out harmful ultraviolet and other rays from the sun. Such scholars maintain that the water from the Great Flood came from this layer, and that this is why it is no longer present in the atmosphere.
Robert Heinlein wrote a science fiction series about rejuvenation and a project called the 'Howard family' that was working to extend the human lifespan beyond 150 years - the first volume was called Methuselah's Children.