The Evolutionary and Biophysical Determinants of Maximum Lifespan: Scaling Laws, Brain Size, and Future Projections

Abstract

The lifespan of all organisms is determined by an interplay of genetic architecture and environmental conditions. Within a population, the lifespan of the longest-lived individual defines the Maximum Lifespan (MLS). For contemporary Homo sapiens, this value is approximately 113 years, with verified records suggesting a potential upper bound of 115-120 years. Throughout human history, average life expectancy has increased dramatically. In early hominin populations, average lifespan was around 30-40 years, rising to about 60 years in the 20th century, and currently averaging 70-80 years in developed nations. This increase has significantly facilitated cumulative knowledge transfer and cultural complexity across generations. For modern humans, with a brain volume of ~1,446 cm³ and an observed MLS of ~95 years, the value calculated by this formula (~92 years) shows strong concordance. For instance, if human MLS were to increase to 200 years, brain volume would need to expand to approximately 5,688 cm³, body mass would also increase, and daily caloric intake would rise to ~1,523 kcal. This radical change would also affect reproductive strategies; the onset of sexual maturity could be delayed from the current 14-17 years to 30-37 years in a 200-year MLS scenario. In conclusion, focusing on a single mechanism—such as somatic mutations—is insufficient for understanding the limits of the human lifespan.