In 2012 the U.N. estimated the existence of 316,600 centenarians among the world seven billion inhabitants. A little over 53,000 of them are in America, more than in any other nation. In 1950 there were only 23,000 centenarians in the world or about fourteen times fewer than we see presently. Yet, the world contained less than four billion people in 1950 and population has only doubled since then. We can then easily see that the centenarians are growing far more rapidly than the population as a whole.
In a general way it is easy to see why this is the case. Improvements in medicine and public health have led the way. Increasingly, the factors that appear to cause people to live past 100 years favor a diet heavy in grains, fish and vegetables, but light in meat, eggs and dairy. They generally have low stress lifestyle, and have rarely been seriously ill. They have generally lived in caring, socially harmonious communities and have always had a high activity level which may include walking and gardening. They often have an active spiritual life which also reduces stress.
Aging is a hopefully slow, yet unremitting march toward eventual death which we all hope will come later rather than sooner. We succumb from genetic defects, inherited or acquired over time, infection, poor metabolism, accidents or chronic disease. Improved medical care, vaccines hat protect against infectious disease, improved diet, safe food, removal of toxins from the environment, and reduced tobacco use have helped expand life expectancy.
Anti-aging drugs are being considered as are even nanotechnologies & nanorobotics which many have suggested may further remedy the effects of aging by 2030. Use of stem cells, tissue engineering strategies, removal of chromosomal altering machinery that may be activated later in life, targeted killing of harmful cells, and subtle immunotherapy all sound like impossible strategies now, but are nevertheless coming and are likely allow many of us to live live longer and longer into the future. Some of this to both us and to our decendents will likely appear as indistinguishable from magic as we begin to see such strategies unfold.
The maximum theoretical life span in years may be much longer than we can presently imagine. Yet it may be longer that we might guess but certainly not infinite. We may extend and repair, tweaking our biological mechanisms until we can no longer squeeze out any more time.