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Life expectancy – the timeline for humans
Life expectancy is the average expected lifespan of an individual; it varies considerably according to geography, economic condition, class and gender. Life expectancy rises sharply in all cases for those who survive childbirth and early childhood to reach puberty.
The people we call the Neanderthals, living in Europe 60,000 years ago, are thought to have lived an average lifespan of 20 years. Our ancestors, homo sapiens, living 40,000 years ago had about the same lifespan. Then, what we call civilization began to appear in human societies, with cities and agriculture forming new ways of living. The average lifespan of citizens in ancient Rome was about 30 years. By the end of the 19th century in Europe the average lifespan was 33, and by the early 20th century it had risen to almost 40 years.
By the 1940s, the average lifespan in most developed countries stood at about 50 years. Public health measures are credited with much of the recent increase in life expectancy. During 20th century, the average lifespan in the US increased by more than 30 years,, 25 years of which can be attributed to advances in public health.
As we saw comparing Swaziland to Japan, there are great variations in life expectancy worldwide, mostly caused by differences in public health, medical care and diet from country to country. Climate may also have an effect. Andorra, a tiny (pop 72,000) mountainous country in the Pyrenees Mountains between Spain and France has the world's longest life expectancy of 83.5 years. Residents claim their stress-free lives in a congenial climate are the reasons.
There are significant differences in life expectancy between men and women in developed countries, with women outliving men by five years or more. These gender differences have been lessening in recent years, with men's life expectancy improving at a faster rate than women's. Poverty, in particular, has a very substantial effect on life expectancy. In many developed countries life expectancy in the wealthiest areas is on average ten years longer than in the poorest areas and the gap appears to be increasing.
The following statistics apply in general to people in developed countries and in many of the advanced developing countries as well. Women tend to have a lower mortality rate at every age. In the womb, male foetuses have a higher mortality rate (males are conceived at a ratio of about 124 males/100 females, but by birth, the ratio is only 105 males/100 females). Among the smallest premature babies (those under 1 kilo/2 pounds), females have a higher survival rate. At age 110, about 90 percent of the population is female, and this increases still higher to about 92 percent by age 112.
The most commonly accepted view among scientists is that there is probably an absolute upper limit to human lifespan of no more than about 125 years -- the oldest person with an authenticated birth record was a French woman called Jeanne Calment, who died in 1997 aged 122 years, five months and 14 days.
Some 60 percent of boys and 70 percent of girls born in 1981 are expected to survive to celebrate their 75th birthday in 2056. In 1881, only a third of girls and just one in five boys reached the same age. The generation of the Baby Boom is setting many records, with each of us facing the new reality that a long and healthy life is becoming more common than ever before. |
