Telomeres are repetitive DNA caps at chromosome ends. In humans, the repeating motif is TTAGGG. They exist because linear chromosomes cannot be copied perfectly all the way to the end during normal DNA replication. Each cell division leaves a small amount behind, so the telomere gradually shortens over time.

This is known as the end-replication problem, and it is one reason replicating cells carry a built-in countdown. When telomeres become critically short, the cell interprets that as a damage signal and shifts toward a senescent, growth-arrested state.

Telomerase is a reverse transcriptase that adds telomeric repeats back to chromosome ends. It is active in stem cells, germ cells, and most cancer cells, but comparatively quiet in most adult somatic tissue. That difference is why telomerase attracts so much attention in aging biology: it looks like one of the cleanest molecular levers for delaying replicative exhaustion.

The classic Hayflick limit — roughly 50 to 70 divisions for human fibroblasts — is closely tied to telomere length. Cells that maintain telomeres can divide longer. Cells that cannot eventually stop.

Epithalon is studied because of reported telomerase reactivation effects in somatic cells and associated telomere-length findings. Whether that literature ultimately scales into broader aging biology is an open question, but the mechanism is clear enough to justify its place in longevity research.

Understanding telomere biology helps separate compounds that target the replicative clock from compounds that target mitochondria, metabolism, or antioxidant signaling. That distinction matters when researchers say two longevity compounds both affect aging but actually intervene at completely different levels.