1.8 million-year-old human jawbone discovered in Republic of Georgia — and it may be earliest evidence yet of Homo erectus

A roughly 1.8 million-year-old Homo erectus jawbone discovered in the Republic of Georgia may be evidence of one of the earliest human groups to live outside Africa.

The discovery, announced July 31 by the Georgian National Agency for Cultural Heritage Preservation, sheds new light on the evolution of our genus, Homo, and "is expected to reveal the reasons for the migration of early hominins out of Africa," Giorgi Bidzinashvili, an archaeologist at Ilia State University in Tbilisi, told Live Science in an email.

Bidzinashvili has been leading an excavation at the early Stone Age site of Orozmani, about 60 miles (100 kilometers) south of Tbilisi, Georgia's capital, since 2020. In those early excavations, researchers discovered stone tools near ancient animal bones, as well as a single tooth from H. erectus, which they unearthed in 2022.

H. erectus evolved around 2 million years ago in Africa. It was the first human ancestor to leave Africa, and explored parts of Europe, Asia and Oceania. The earliest fossil evidence of this journey comes from the site of Dmanisi, which is just 12 miles (19 km) from Orozmani.

In a 2011 study, chemical dating of the lava flows on top of Dmanisi and Orozmani showed that the sites are roughly contemporaneous. Both date to between 1.825 million and 1.765 million years ago.

Excavations at Dmanisi over the past three decades have revealed more than 100 fossil bones, including five skulls. Those skeletons showed that the earliest hominins to leave Africa were significantly shorter and had smaller brains than Homo sapiens. The Dmanisi skeletons were initially given the species name Homo georgicus, but they are now generally considered the earliest known H. erectus individuals in Eurasia.

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So far, the Orozmani fossils, which include just one tooth and one partial jaw, are not as numerous as those at Dmanisi. "Since we have not yet cleaned the jaw," Bidzinashvili said, "it has not been compared with the Orozmani tooth from 2022."

But the discovery of fossils at Orozmani suggests that Dmanisi was not a unique site. Several early human groups may have settled in the Caucasus soon after leaving Africa.

"Maybe we're seeing that this movement to Georgia wasn't an isolated incident, but maybe there was a broader distribution of Homo erectus in this time period," Karen Baab, a biological anthropologist at Midwestern University in Glendale, Arizona, who was not involved in the research, told Live Science.

The research team is trying to figure out whether one site is older than the other.

"Until we have new dates, we can neither confirm nor deny that the Orozmani human fossils are older than Dmanisi or contemporaneous," Bidzinashvili said. "By the end of the year, we will know."

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