How would you explain people living 900+ years, as recorded in Genesis, in scientific terms? How was this possible?
Present experience and scripture show that we might live “seventy, or even by reason of strength eighty….” (Ps. 90:10) Scientific examination has shown a number of biological reasons for this to happen. Consequently, there is now speculation about how life may be extended. Even today with modern health advances life expectancy is much greater than it was 100 years ago. During the 20th Century life expectancy has increased from about 50 years to almost 80 years.
Lifetimes similar to Moses’ 120 years are now beginning to occur. Our bodies have remarkable mechanisms for repair. Cells even have mechanisms that can repair damage to their DNA. So it would seem that very long lifetimes could be possible given certain biological changes. Present research (see “Resources”) has identified many biological impediments to very long life. But, some researchers are still optimistic that medical advances could make very long lifespans possible. Consequently, we have reason to believe that the long lifetimes given in scripture for the patriarchs were literal. But, if that is true the interesting question is how those came to cease.
There have been a number of speculations put forward but I think it is dangerous to speculate too much about what might have occurred. I will give two examples that I have heard. One is that a nearby supernova bathed the Earth in radiation which damaged the DNA of early man. A supernova leaves remnants of gas and debris called a nebula. So, we should be able to find some evidence in some diffuse nebula for that event but I have yet to see anything convincing. Such nebulae could be difficult to detect. Another speculation that has been discounted is that the early earth was protected by some atmospheric mechanism from solar radiation. This was tested by raising mice in a deep mine shielded from cosmic rays. This did not result in any effect on longevity. Also against this idea is the fact that a certain small amount of radiation appears to be necessary to stimulate repair mechanisms. I have not heard or read of any real evidence of a condition that would have allowed the patriarchs to live to greater ages.
Another possibility that has been put forward is that the long ages are intended to indicate the status of the patriarchs. That is the ages reported are exaggerated to reflect this status. Examples have been given where this happens in extra-biblical literature. I am not a fan of this explanation given the explicit wording of the text in Genesis 5. However, a similar explanation might be that the names given represent dynasties where the name is the name of the head of a line of lesser descendants. The fact that it can be shown that lineages given in scripture occasionally omit individuals might give some weight to this view. Nevertheless, I do not find this convincing either.2
Consequently, I have to admit that the above discussion is perhaps interesting but speculative. I think I must leave this question open. We just have the declaration from scripture that ancient man lived much longer than we do now. Interestingly during the millennial reign of Christ man will once again experience an extended lifespan (Isa. 65:20). How this will happen is not specified in Scripture. As mentioned above scientific studies are currently seeking to understand the process of aging. Possibly future discoveries will solve the aging problem as it is called.
Liochev, Stefan, Which Is the Most Significant Cause of Aging? (Antioxidants (Basel). 2015 Dec; 4(4)) 793–810.
1. I appreciate you pointing out that science is ill equipped to answer this kind of question with any certainty. Science deals primarily with the present and hypothesizing on the the past using present paradigms and tools to look into the past. These fare poorly when dealing with those who died without leaving evidence we can test. (Daniel Hayes, Ed.)
2. Another possibility is that genetic loading (the cumulative increase of mutations within a population) increased in the population over generations and helped to limit lifespans, especially after the flood when meat was introduced into the diet (Gen. 9:3). (Ed.)