Biological immortality

A biologically immortal living being can still die from means other than senescence, such as through injury, poison, disease, predation, lack of available resources, or changes to environment.

Prior to Leonard Hayflick's theory, Alexis Carrel hypothesized that all normal somatic cells were immortal.

One way to induce immortality is through viral-mediated induction of the large T-antigen,[10] commonly introduced through simian virus 40 (SV-40).

[17] Key molecular mechanisms of its rejuvenation appear to involve DNA replication and repair, and stem cell renewal, according to a comparative genomics study.

[24] Their longevity may be due to telomerase, an enzyme that repairs long repetitive sections of DNA sequences at the ends of chromosomes, referred to as telomeres.

Older lobsters are also known to stop moulting, which means that the shell will eventually become damaged, infected, or fall apart, causing them to die.

Studies on genus Schmidtea mediterranea suggest these planarians appear to regenerate (i.e. heal) indefinitely, and asexual individuals have an "apparently limitless [telomere] regenerative capacity fueled by a population of highly proliferative adult stem cells".

[30] For sexually reproducing planaria: "the lifespan of individual planarian can be as long as 3 years, likely due to the ability of neoblasts to constantly replace aging cells".

Whereas for asexually reproducing planaria: "individual animals in clonal lines of some planarian species replicating by fission have been maintained for over 15 years".