Scientists said the breakthrough find could prove that modern humans may have left Africa as much as 100,000 years earlier than was previously thought.
It may also cause rethinking about how we evolved and interacted with now-extinct cousin species, such as Neanderthals.
"When they start moving out of Africa and what geographical route they choose to do it are the two most important questions in recent human evolution," said Tel Aviv University anthropologist Israel Hershkovitz, lead author of a study published in the journal Science.
The jawbone, complete with several well-preserved teeth, which was discovered in Israel, was found to be somewhere between 177,000 and 194,000 years old.
Previously, the oldest fossils of modern humans found outside of Africa were somewhere from 90,000 to 120,000 years old, also in Israel. So given the range in both those estimates, the jawbone might be about 50,000 to 100,000 years older.
The jaw was found in 2002 in the collapsed Misliya cave on the western slope of Mount Carmel. Researchers spent the last decade-and-a-half looking for more remains and other fossils before publishing their study.
They say the jaw belonged to a young adult of unknown gender.
The Science paper suggests modern humans could have left Africa 220,000 years ago, with some of the authors saying maybe it was even earlier.