A 100-year-old lobster is, by most biological measures, as vigorous as a 10-year-old one. It is also larger, more fertile, and in some respects more robust. If aging is a biological clock running down, lobsters are doing something to the clock.
Most animals show the standard signs of aging over time: cells stop replicating, tissues degrade, organ function declines. Lobsters do not. Rather than slowing down with age, they appear to keep going, at least until something outside their biology kills them.
The reason involves an enzyme called telomerase. In most animals, cell division gradually shortens structures called telomeres at the ends of chromosomes. After enough divisions, the telomeres become too short for the cell to divide safely, and the cell stops replicating or dies. Lobsters produce telomerase in unusually high quantities throughout their entire body, not just in germ cells as most animals do. This enzyme repairs the telomere length after each division, effectively resetting the clock.
The practical consequence is that lobsters do not have a natural lifespan the way most organisms do. They do die, but mostly from external causes: predation, disease, the physical stress of molting, or the fact that larger lobsters eventually require so much energy to complete a molt that the molt itself kills them. Without those external pressures, the theoretical biological ceiling is much higher than for almost any other animal we know of. This is not immortality in any useful sense. But it is a genuinely different relationship with time than the one most living things have.
