Summary in Seconds: Scientists have identified what may be the ultimate biological limit to human lifespan. A new study suggests that even if every reversible aspect of aging and all age-related diseases could be eliminated, the relentless buildup of random DNA mutations in our cells would still cap the median human lifespan at about 146 to 194 years. The greatest limitation comes from long-lived, non-renewing cells in the brain and heart, which gradually accumulate irreversible genetic damage. While somatic DNA mutations appear to be a major driver of aging, the researchers found they account for only about half of the