June 29 (UPI) -- There could be no limit to how long humans can live, according to a new study.
Biologists Bryan G. Hughes and Siegfried Hekimi at Canada's McGill University studied the longest-living people from the U.S., Britain, France and Japan since 1968 and came to the conclusion that the human body doesn't have a maximum age limit.
"We just don't know what the age limit might be. In fact, by extending trend lines, we can show that maximum and average lifespans, could continue to increase far into the foreseeable future," Hekimi said.
Hekimi pointed out that the average life span has greatly increased over the past few decades and should continue to do so.
"Three hundred years ago, many people lived only short lives. If we would have told them that one day most humans might live up to 100, they would have said we were crazy," he said.
During the 20th century, the average lifespan for Americans increased by about 30 years between 1900 and 1998.
According to the University of California at Berkeley, in 1900, men could expect to live until the age of 46 and women typically lived until 48.
By 1998, the average man's life lasted 73.8 years, while women lived for 79.5 years.
Today, men can expect to live for 76.5 years and women tend to live for 81.2 years.
However, 2015 saw the first decline in the average life expectancy in the U.S. in 20 years as the average for both sexes dropped slighty to 76.3 for men and 81.2 for women.
Heart disease could be a factor. The number of Americans who died from heart disease increased in 2015 with 168.5 deaths per every 100,000 people.