(this became a chapter in "Demystifying Machine Intelligence")

• Progress in medicine is credited with extending life expectancy.
• While antibiotics and vaccines certainly did so, it is not clear that most other pills and surgery are adding much to life expectancy
• The other major factor that contributed to extending life expectancy is affordable professional health care. Health care used to be the responsibility of the family, and then shifted towards the state. The state can provide more scientific health care, but it is expensive. When that professional health care became affordable, the general population started feeling the benefits.
• The future promises more medical progress (particularly in biotechnology), which leads many to believe that life will be extended dramatically.
• However, health care has become too expensive for governments to continue paying it for the general population, and the professional health care that the average citizen receives may already have started to decline, and may continue to decline for a long time. It is just too expensive to keep the sick elderly alive forever for all the healthy youth who have to chip in.
• To compound the problem, statistics indicate that the number of people on disability programs is skyrocketing (14 million people in the USA in 2013, almost double the number of 15 years earlier)
• Virtually every society in the world is moving towards a larger base of elderly people and a smaller base of younger people who are supposed to pay for their health care. This equation is simply not sustainable.
• At the same time the tradition of domestic health care has largely been lost. You are on your own.
• This parallel development (unaffordable professional health care combined with the disappearance of domestic health care) will reverse the longevity trend (that was due mostly to affordable professional health care) and lead to a worse (not better) chance of living a long life.
• Furthermore, the rate of suicide has been increasing steadily in most developed societies, and it usually goes hand in hand with a decline in birth rate. This might be an accelerating loop.
• The country with the oldest people is Japan. That is also one of the countries with the highest suicide rates of all, and most of the suicides are committed by elderly people. Getting very old does not make you very happy.
• The USA is one of the most advanced countries in the world. In 2013 the Center for Disease Control (CDC) found that the suicide rate among middle-aged people had increased 28% in a decade (40% for white people) and that since 2009 suicide had become the 10th leading cause of death in the country, overtaking car accidents.
• As all countries reach the point of lower health care and accelerating suicide rates, life expectancy might actually start to decline for the first time in centuries.
• (Jeanne Louise Calment died at the age of 122 in 1997. Since then no person in the developed world (where we can verify the age) has died at an older age. Even if we believed the claims from various supercentennarians in developing countries (countries in which no document can prove the age of very old people), we could hardly credit their achievement on technological or medical progress since those supercentennarians lived all their lives with virtually no help from technology or medicine. In other words, the real numbers tell us that in almost 20 years nobody has reached the age that someone reached in 1997. It takes a lot of imagination to infer from this fact that we are witnessing a trend towards longer lifespans.)
• There is also be a shift in value perception at work. The idea that the only measure of a life is the number of years it lasted, that dying of old age is "better" than, say, dying in a car accident at a young age, is very much grounded in an old society driven by the survival instinct: survive at all costs for as long as possible. As the (unconscious) survival instinct is progressively replaced by (conscious) philosophical meditation in modern societies, more and more people will decide that dying at 86 is not necessarily better than dying at 85.
• In the near future people may care more about other factors than the sheer number of years they lived.
• The attachment to life and the desire to live as long as possible is largely instinctive and irrational.
• As generations become more and more rational about life, it may not sound so attractive to live long lives if one has to die anyway and be dead forever and be forgotten for the rest of eternity.
• What is the best age at which to prolong life? I doubt people are excited at the idea of getting older and older, as in "decaying". When people want to live to 150 they want to live to 150 and still be able to play tennis, read books and have sex. At which age should we stop the aging process? 60? 40? 20? 10? 4? 1?

• Antibiotics, filtered water, cesarean section childbirths, smaller looser families and other environmental and behavioral changes greatly weaken the beneficial bacteria that constitute the physical majority of the cells of the human body
• Vaccinations are useful to prevent children from dying of horrible diseases, but now they are becoming mandatory for every possible disease (and for the mere possibility of a disease). We are gradually engineering a completely artificial immune system whose side effects are largely unknown.
• Many of today's habits (including some that are meant to protect us from diseases) may result in weaker immune systems, or at least partially weaker immune systems which would succumb to new unknown viruses.
• No new classes of antibiotics had been introduced since 1987 whereas new pathogens are emerging every year, and existing bugs are developing resistance to current antibiotics. If the situation is not remedied by new more powerful drugs, humanity will return to the situation of the 19th century, when infections killed people as a result of routine operations.
• On the same March 2013 day that a symposium in Australia predicted drugs to slow the ageing process within a decade so that people can live to 150 years (link) the Chief Medical Officer for England, Dame Sally Davies, raised the alarm that antibiotics resistance may become a major killer in the near future link
• Personal mobility has greatly increase the chances that a deadly epidemics spreads worldwide killing millions of people
• We now routinely eat genetically-manufactured food whose effects over the long time rest ot be determined
• Parenting at later ages defies the biological clock, increasing the chances of birth defects and problems at later age in the babies born to older parents
• Nobody knows its causes and it is difficult to speculate on the effects, but there is now scientific consensus that the quality of sperm has deteriorated over a few decades (See this article). Male fertility is increasingly under threat. More importantly, it might result in children that are less healthy than previous generations.
• Even the smallest of nuclear wars (say Pakistan-India) would cause a worldwide decline in longevity
• At a personal level, i keep finding the younger generations are sicker than my generation, hence the feeling that we are creating sicker and sicker generations. My generation grew up helping older people carry heavy loads, go shopping for older people who were sick with the flue, and so forth. Now it's the young who have all sorts of physical problem that keeps them from lifting heavy loads and who get sick of every passing germ. They need a dentist all the time, they get food poisoning the moment they cross a border, and they start taking all sorts of pills in their 30s. I don't see how this bodes well for our race's longevity.
• Studies (e.g. Dana King's 2012 study based on data from two US National Health and Nutrition Examination surveys) show that the "baby boomer" generation is less healthy than the previous generation.
• We are building a weaker and weaker species while creating a more and more dangerous world.