Early humans had the same life expectancy as their ancient cousins before Neanderthals died off about 30,000 years ago.
Why the Neanderthals disappeared just as modern humans were making huge gains has long puzzled scientists.
Fossil records of early modern humans and Neanderthals reveal "similar patterns of adult mortality."
Higher fertility rates and lower infant mortality likely gave modern humans an advantage over the Neanderthals.
Dying young was not likely the reason Neanderthals went extinct, said a study out Monday that suggests early modern humans had about the same life expectancy as their hairier, ancient cousins.
Scientists have puzzled over why the Neanderthals disappeared just as modern humans were making huge gains and moving into new parts of Africa and Europe, and some have speculated that a difference in longevity may have been to blame.
If anything, higher fertility rates and lower infant mortality gave modern humans an advantage over the Neanderthals, who died off about 30,000 years ago, said the study in the Proceedings of the National Academy of Sciences.
Scientist Erik Trinkaus of Washington University studied fossil records to get an idea of the life span of Neanderthals and early modern humans, who co-existed in different parts of the world for about 150,000 years.
He found about the same number of 20- to 40-year-old adults in both populations, an indication that would reflect "similar patterns of adult mortality," said the study.
"All the samples have a dearth of older individuals, which should reflect a complex combination of low life expectancy for adults, demographic instability, and the demands of mobility," he said. "If indeed there was a demographic advantage for early modern humans, at least during transitional phases of Late Pleistocene human evolution, it must have been the result of increased fertility and/or reduced immature mortality."
The squat, low-browed Neanderthals lived in parts of Europe, Central Asia and the Middle East. Their last known refuge was Gibraltar.