We should, however, trust most of the Biblical Genesis chronology. They knew what a "day" and a "year" were, and had the same sort as we do. We need not assume that a "900 year" life span really means a "90 year" one or anything of that nature.
Along with these longer life-spans, we should assume an appropriate adjustment of all the aspects of human life. That is, instead of puberty starting at 13, it starts at 130, instead of menopause starting in the, well, whenever it starts (I'm a dude, I don't have to know that stuff) it starts in the 500s, 600s, or 700s, or whatever. This maintains the same humanity that we've got while drastically increasing the available child-bearing years (I assume that gestation is still 9 months...)