Life expectancy is an average, and it fluctuates with age as the risks we face change throughout our lifetimes. Both those facts make it a frequently misunderstood statistic, The New York Times reports.
High infant-mortality rates depress the figure substantially.
This can lead contemporary observers to the false conclusion that most humans died quite young, even in the not-so-distant past.
Before the Upper Paleolithic, early humans really did die young, most before their 30th birthdays. Then, during the late Stone Age, there was a significant increase in the number of people living into older adulthood.
Rachel Caspari, a paleoanthropologist at Central Michigan University, found that beginning around 30,000 years ago, during the Upper Paleolithic, there was a demographic shift : Caspari counted 20 old adults for every 10 young adults, coinciding with an explosion of cultural production
Currently, life expectancy at birth in the United States is roughly 79 years, and it’s the same at age 25, but our gains have slowed considerably.
The biggest barriers to improving life expectancy in the United States are societal issues, says Justin Denney, assistant professor of sociology at Rice University, such as growing up in a lead- and asbestos-contaminated row house or generations of chronic stress.
“Look at the countries with the highest average life expectancy,” says Denney, referring to places like Japan, Australia, Canada and, Sweden — nations that distribute their health resources more evenly. “Ultimately,” he says, “life expectancy is a measure of quality of life.”