In 1750, life expectancy at birth in France was 27 years for men and 28 years for women. Today, it is around 78 years for men and 85 years for women. On a global scale, it rose from 46.5 years on average in the 1950s to 68.5 years in 2011. This represents an increase of almost 4 months a year which can be explained by improvements in medicine and hygiene and better access to healthcare.
Some forecasts estimate that life expectancy will continue to increase but the trend could reverse. Firstly because the human life span probably has a biological limit but also because diseases are still killing people in spite of medical progress. In South Africa, AIDS has lowered life expectancy at birth by 12 years over less than 20 years, whilst on a global scale the number of chronic disease cases keeps increasing. The effects of these chronic illnesses may not yet be glaringly obvious but according to the World Health Organisation (WHO), they have already overtaken infectious diseases as the leading cause of death in the world.
Among these chronic diseases, obesity is attracting a lot of attention. Indeed, even though it lowers life expectancy by 5 to 15 years, 43 million children under 5 years old were overweight in 2010. Similarly, the number of cancer cases in the world is increasing sharply throughout the world (an estimated +45% between 2007 and 2030, according to the WHO), partly because of the ageing population, but also, most probably, because of environmental factors.
Unbalanced food contaminated by pesticides, sedentary lifestyles, air and water contaminated by synthetic chemical pollution and environmental problems in a broad sense are new phenomena which appeared in the 20th century. We have only just begun to see their effects and they could give the current generation of babies a shorter life expectancy than their elders.