Researchers are now suggesting that male and female lifespans continue to increase linearly, and have not yet hit a hard limit. Previous studies argued that human life expectancy is increasing by less and less each year, but that is only because it was studied in the wealthiest countries. The omnipresence of that questions explains why humans have a history of trying anything to defy the finality of death. (This is also not a new assumption—humanity was thought to have approached its upper limit to life expectancy as far back as 1990.) Male lifespans have increased by an average of 2.03 years per decade since 1840, and female lifespans increased by 2.31 years per decade in that same time frame.