First, some Christian scholars will try to step around this problem by insisting that the long life-spans of the antediluvians (Pre-Flood greats like Seth, Enosh, Methuselah etc) is metaphorical. Perhaps, it is suggested, these recorded ages were an indication of their importance culturally/ religiously, or analogous to something else, like the generations that revered them, or the amount of their learning, OR some numerological significance now lost to us. For an interesting look at this view, see BioLogos give it a whirl: here.
But as you will see, they don’t offer sound reasons WHY the ancients would mark ages in this way (# of years = something other than years), or why they would then switch to marking age in a normal way (# of years = 365 day periods of life). And the numerological math they do in this article is dizzying and frankly too convoluted to be convincing. It feels too “ad hoc” – that is, contrived specifically to accommodate a uniformitarian view of the past.
Of course rejecting that hypothesis, we’re left with only two options: One is ditching the bible as a truth source. But if you, like I, are inclined to trust the Bible for other reasons, both historical and uncanny, then we have to take these ages seriously, as a statement of actual age, and then see if we can find some harmonization with science and observation which currently says, of course, that people simply cannot live that long.
The hope of finding archaeological evidence for really old humans is going to be difficult. In any world where humans actually live to be 900 years old, the aging process must be entirely different.
Modern CSInvestigators can determine the age of human remains by certain skeletal markers, and they might presume the exact same physical/chemical body processes would be at work to find the same markers in the remains of a 900 year old man. But can we reasonably assume this? The remains of a 900 year old man, if he aged under the same physical and chemical burdens we observe today carried out over 9 centuries, would look like a shriveled shell, a totally c-shaped, decrepit, living fossil, whose bones would be so brittle, so small, and so malformed, it would be practically unrecognizable as human remains. If this is the evidence we’re looking for, it seems predestined to never be found.
More reasonably, we have to assume that to live that long, something about the way we currently age (and therefore the way we assess age in human remains) would HAVE to be different than it is now. So this would change our task in finding corroborating evidence for the bible’s claim that ancient people lived very long lives. Instead of finding people who display the same aging processes/makers, only sustained artificially over centuries, we should look for some evidence that aging itself as we know it, is plausibly changeable, and could be different under different conditions. This sort of evidence is more reasonable to come by.
So at Reasons To Believe, Hugh Ross and company go into the details of what we currently know causes aging. In some ways, I was surprised to learn that the human can (and maybe was designed to) live much longer than the current outer limit of 120 years (which BTW, matches God’s judgment in the Bible in Genesis 6:3). In other words, rather than early death being “natural” and 900 year life spans being “unnatural”, when you consider what look like governors on aging, the truth may be the reverse.
In studying fruit fly aging, it looks as though a genetic mutation in the current population ensures shorter life spans – and when that gene is altered, the flies can live literally 100% longer. Other factors are considered, including large scale radiation from a specific supernova event which we now know coincided with early human development (and perhaps the time just before the flood, 40,000 years ago). We know radiation plays a role in cellular breakdown and thus faster aging. The increase in radiation from a celestial event like that also explains the gradual decrease in recorded ages in the Bible (from pre to post flood) rather than an immediate reduction right after God’s decree. See all their lines of evidence in the article posted here: Reasons to Believe.
Finally, there is a bit of circumstantial evidence that is corroborative while not convincing all on its own. That is, the fact that the Bible is not alone in attributing long ages to people who lived in the ancient past. The Egyptians and the Sumerians also have lists of ancient kings who lived very long indeed. In fact, by comparison the ages of the Bible’s antediluvians is sober and positively conservative! One Sumerian king was said to rule for 28,000 years! What’s interesting is that these extra-biblical sources not only show long ages for those who lived before a great flood, but also that the ages quickly reduced directly after the flood. To get a feel for what those Sumerian sources reveal, look here: Old Sumerian Kings.
In any event, the existence of long-lived predecessors presents us with an opposing view of humanity. The current one is that people are continually upgrading through micro mutations into something better and better, but the antediluvians suggest that the human genome was in a purer (more fit) state in the past, and that people are continually degrading through mirco mutations – devolving rather than evolving. John Sanford wrote a book called Genetic Entropy that makes the claim that devolution in terms of the human genome is a well-established fact. Check out this video of him, beginning at 13:08: John Sanford – Human.