Biological Immortality
Biological immortality refers to the theoretical absence of senescence—the biological process of aging—in living organisms. An organism possessing biological immortality would not experience age-related decline and could theoretically live indefinitely, though it would remain vulnerable to death from injury, disease, predation, or environmental factors. This contrasts with popular conceptions of immortality, which typically imply invulnerability to all forms of death.
Natural Examples
Several organisms demonstrate negligible senescence or show no measurable increase in mortality rate with age. Certain jellyfish species, particularly Turritopsis dohrnii, can revert to earlier developmental stages through transdifferentiation, potentially resetting their biological age. Some tortoises, rockfish, and bristlecone pines show extremely slow aging rates with no clear upper lifespan limit. Hydra, a small freshwater organism, displays no signs of senescence in laboratory conditions, though environmental factors ultimately limit survival.
Research Limitations
Biological immortality remains theoretical in the context of complex multicellular organisms. A 20-year Japanese study on mammalian serial cloning concluded that the process leads to a genetic dead end, with cloned organisms showing accelerated aging and reduced lifespan compared to naturally conceived individuals. This finding suggests that fundamental biological constraints—including telomere shortening, DNA damage accumulation, and cellular degradation—may prevent indefinite lifespans in mammals, even with technological intervention.