According to the stem cell hypothesis of ageing, the ageing process is caused by various types of stem cells' failure to continue replenishing an organism's tissues with functional differentiated cells capable of preserving the tissue's original function. Regardless of the age of the system, damage and mistake accumulation in genetic material is always a concern. Young people have a considerably larger amount of stem cells than older people, resulting in a better and more effective replacement process in the young. As a result, ageing is not a result of increased damage, but rather of a failure to replace it owing to a reduction in stem cell numbers.
