Many Christians simply dismiss the incredibly long lifespans assigned to the early patriarchs in the book of Genesis. Who could believe that several of them lived more than 900 years? Or that Abraham lived even 175 years?
But hey! This is the word of God. We have to come to terms with that, too. How can it be done? Enter Msgr. Pope with some thoughts on the issue. Link
When people start doubting the Biblical account of things, I like to remind them that we are talking about God, the creator of heaven and earth, all that is. Is anything too difficult for Him? He does like to step into His creation and do things outside the ordinary from time to time.