How would a person account for the ages recorded the book of Genesis from Adam to Isaac?
All the people you suggested are considered part of the pre-deluvian, or pre-flood, age. The only thing that tells us how old these people were is the genealogies. It may be surprising to modern readers to see how long people lived before the flood.
So let me start at the beginning with the Garden of Eden. The Bible doesn’t tell us how long between the six days of creation and the time of the Fall of Man. The first indication we get of time passing or the ages of human beings is from the birth of Seth (Genesis 5:3). Adam has Seth when he is 130 years old.
But we know from Genesis 4 that he had at least two other sons, Cain and Abel. Why does the Bible start with Seth? It’s almost like a restart after the problems with Cain and Abel. Genesis is the book of starts and restarts.
While he was in the garden, and we don’t know how long he was, there was no understanding of death. We have no indication if those 130 years started in the garden or after he was kicked out of the garden and death was now a factor.
The ages of humans from Adam onward are quite large sums. The reason for this is that other than the proclamation of death beginning with the sin of Adam and Eve in the garden, humanity was gradually becoming more sinful.
Sin was not a large enough factor forgot to change the age of man until the great sins happening right before the flood (Genesis 6:3). There may be an indicator that God’s Spirit also prolonged the age of humanity until God declared the 120 year limitation.
He never limits the age of humanity again. And it takes a while before that 120 years becomes the norm among human beings. Even after God declares this, Noah lives much longer. He was already on his way before God made this declaration.
Until humanity transgressed God’s laws to the point that they did in Genesis 6, where Angels were crossing God’s line with human women, God allowed humanity to progress into longer lifespans. The longer lifespans also helped grow the population of the earth. People lived much longer and had many more children.
No matter how long people lived on the earth before the flood, only Noah, his wife, his three sons and their wives, are the only ones to survive. Everyone else, no matter their age, dies in the flood. I consider the pre-flood era to be a time where God allowed humanity to live longer until they crossed the line. Then he not only ended the long lifespans but their lives.
The Bible has a hard-line principle that sin leads to death. The beginning of Genesis is no different. People lived long until their sins caught up with them. And when sin crossed God’s line he reduced the age and started over.