Apr 12, 2018

Humans left Africa far earlier than we thought

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Data: Sites compiled from various science journals; Map: Andrew Witherspoon/Axios

The stories of our distant ancestors — when and how they evolved into the Homo sapiens we are now, and how they migrated and eventually populated the world, often center on an exodus of modern early humans from Africa about 60,000 years ago.

What's new: A growing number of researchers believe while there may have been a main migratory event then, recent findings and new technology reveal that groups likely traveled out of Africa and its bordering Levant region earlier than previously thought. The map above by Axios' Andrew Witherspoon shows some of these recent findings.

Recent findings

1. Al Wusta region of Saudi Arabia. This week, researchers announced they found what they believe is the oldest "directly dated" H. sapiens fossil — a finger bone, dated 88,000 years old via radioisotope testing. The team, led by Michael Petraglia and Huw Groucutt, also found stone artifacts and animal bones.

2. Mount Carmel, Israel. A ridge of teeth and part of an upper jaw that "appear to be human" (they named it "Misliya") was discovered in a cave there. The team, led by Israel Hershkovitz, dated the items as from 177,000–194,000 years ago, using microCT scans and 3D virtual models and compared it with other hominin fossils from Africa, Europe and Asia.

3. Lida Ajer cave site in West Sumatra, Indonesia. Kira Westaway and colleagues hunted down the site after it was first reported 120 years ago by Dutch paleo-anthropologist Eugene Dubois (of the "Java Man" fame), who had brought back some ancient teeth and drawings of the cave. They re-examined the teeth and found they are from H. sapiens that lived between 63,000–73,000 years ago.

4.  Dhofar Mountains in southern Oman. 800 artifacts believed to be roughly 106,000 years old were found in ancient riverbeds. They used a dating technique that measures how much radiation a mineral has absorbed over time. However, no fossils were found and while the authors say the artifacts' craftsmanship points to known African H. sapiens, others are not 100% sure it was not a different type of hominin.

5. Madjedbebe, a rock shelter in northern Australia. Researchers found a site with distinctive stone tool assemblage including grinding stones but no fossils. They dated the deposits near the artifacts to be around 65,000 years ago, using radiocarbon (14C) and other techniques.

6. Luna Cave,  Guangxi Zhuang Autonomous Region, China. A team found two "likely modern human teeth" (although there is debate on what stage those humans were at). Using multiple uranium testing, they estimate the teeth as between 70,200–127,000 years old.

7. Liujiang Cave, southern China. A modern skull was found in the Liujiang Cave and written about in a book "Human evolution in China" by Xinzhi Wu and Frank Poirier. Testing by different groups often yields different outcomes, but it's generally believed to be at least 68,000 years old but is possibly more than 100,000 years old.

Some perspectives

Chris Clarkson, archaeologist from University of Queensland in Australia, told Axios that the finger bone find from Arabia and other recent discoveries support some earlier migration.

" It remains unclear if this was part of a single migration wave or multiple waves, but the new study provides evidence for the right species in the right place at the right time for an eastward migration that went on to colonize Asia and Australia."

Richard Potts, paleoanthropologist and director of the Smithsonian Institution Museum of Natural History's Human Origins Program, told Axios earlier this week that in general paleoanthropologists think H. sapiens were located in the Levant region bordering Africa 100,000 to 130,000 years ago. And this, he says, indicates "a potentially widespread seepage of sapiens groups beyond Africa, even if only initial, temporary, and low-level in terms of population size."

"The finds in Arabia extend the known geographic area of this early dispersal of Homo sapiens, and it indicates that a distinctly sere area of Arabia today was sufficiently 'green' and wet to support human populations."

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