Christians, do you believe that biblical extreme ages are based on solar years, or lunar years?

The Bible gives the age for Methuselah at 969, but study of skeletal remains throughout history have shown that humans are living longer now than ever before. This longer lifespan is due in part to: more adequate diet, better sanitation, modern medicine, and lack of predation. In the past a person was considered very old if they lived long enough to get gray hair (one reason the Roman upper cl died their hair gray, to appear older and wiser). There is no medical explanation for how any human could live to over 900 years in the past, unless we consider the fact that many ancient cultures based their time on Lunar phases, rather than Solar years. If Methuselah's age was given in Lunar cycles, rather than years as we know them, this would give him a very believable age of approximately 79. As for the decrease in age some Bible readers are bound to point out, this would coincide with the spread of the Solar year (seasonal change) as the common measure of time. Anyone care to speculate?