I want to start by saying ever since I was a kid I was highly fascinated aging and greatest mystery how and why we age. Now scientists have found the underlying cells that drive the organisms have built in clocking mechanism. This act as a cell division clock ultimately act as a suicide switch. This switch seems to be in end of our chromosomes. These chromosome ends called thelemears.
Telomeres plays a critical role in aging and age related deceases. Every time the cell divide telomeres get shorten. This is called end replication problem. Once the chromosome lost the end of telomeres and comes to critical stage chromosome will lose the ability to divide. Therefore the cell division will stop.