This chapter lists the generations from Adam through Seth to Noah. Interesting that they lived about 800 years – perhaps the food at that time still retained some potency from the Garden or the environment was naturally conducive to longer life through higher air pressure and oxygen content or the cloudy atmosphere was more UV resilient?
It seems that Methuselah died the same year as the flood. Some think he died before the flood (so that he could be considered righteous) but regardless, he did not seem to stay with or help Noah, and his other children were not considered for salvation from the coming flood. Nor was Lamech’s other sons or daughters saved, though he died a few years before the flood. Noah was an exceptional man.
We seem to get so caught up in the details of Genesis. We argue and fight with each other over those details and suffer righteous indignation if anyone disagrees with us, often going so far as to judge our opponent's eternal fate. Silly. The thief on the cross probably had a poor understanding of biblical history and the process of salvation and yet was saved. Lord, save me in my ignorance too.