Fossil bone discovery pushes back dates of human migration from Africa

According to a new study, the oldest Homo Sapiens fossil finger bone discovered in Saudi Arabia’s Nefud desert has debunked long-held views about human migration out of Africa.

The find, which dates back to 88,000 years ago from a prehistoric lake site in Saudi Arabia, proposes that migration out of Africa was much more geographically widespread than originally thought. Previous studies had concluded that migration was “limited to Levantine Mediterranean woodlands immediately adjacent to Africa.”

On Monday, researchers said the middle bone of an adult’s middle finger found at the site called Al Wusta is the oldest Homo sapiens fossil outside of Africa and the immediately adjacent eastern Mediterranean Levant region, as well as the first ancient human fossil from the Arabian peninsula.

Fossil of an intermediate phalanx bone, 1.2 inches (3.2 cm) long found on the Al Wusta site in Saudi Arabia date to 85,000 years ago, the oldest evidence of human movement on the Arabian Peninsula. Credit: Ian Cartwright

Dating the bone back to 88,000 years ago also corroborates a recent study published in Science which shows that human migration from Africa happened much earlier than commonly thought.

“This discovery of a fossil finger bone for me is like a dream come true because it supports arguments that our teams have been making for more than 10 years,” Michael Petraglia, an archaeologist from the Max Planck Institute for the Science of Human History in Germany and an author on the Nature Ecology and Evolution journal, said during a media briefing.

“Our species first appeared in Africa roughly 300,000 years ago. Scientists previously thought Homo sapiens departed Africa in a single, rapid migration some 60,000 years ago, journeying along the coastlines and subsisting on marine resources,” said anthropologist Michael Petraglia of the Max Planck Institute for the Science of Human History in Germany.

“This supports a model not of a single rapid dispersal out of Africa 60,000 years ago, but a much more complicated scenario of migration. And this find,” Petraglia said, “together with other finds in the last few years, suggests … Homo sapiens is moving out of Africa multiple times during many windows of opportunity during the last 100,000 years or so.”

In addition to the bone, the find also turned up stone tools used by humans. The discovery of fossils of hippopotamus and tiny fresh water snails also shows that Al Wusta was previously a lush grassland teeming with wildlife alongside hundreds of freshwater lakes. To find the remains of Saudi Arabia’s distant, greener past, archaeologists began by looking at satellite images of the region for evidence of prehistoric bodies of fresh water.

“Numerous animal fossils were discovered, including hippos, wild cattle, antelopes and ostriches,” University of Oxford archaeologist and lead author of the study Huw Groucutt said. “Bite marks on fossilized bones indicated carnivores lived there, too.”

“We’ve been to maybe a hundred different sites in Arabia, and almost every one has stone tools,” says Groucutt. “You can’t step out of a car without finding stone tools. The challenge was finding somewhere with human remains. The big question now is what became of the ancestors of the population to which the Al Wusta human belonged,” Groucutt said.

Both Petraglia and Groucutt say the human finger bone found in Saudi Arabia hints at more geographically diverse human migration than previously estimated.

“It conclusively shows that early members of our species colonized an expansive region of southwest Asia and were not just restricted to the Levant.” That evidence, says Groucutt, “casts doubt on long held views that early dispersals out of Africa were localized and unsuccessful”

Excavations at the Al Wusta site which was once a lush grassland awash in lakes and rivers and teeming with wildlife like ostriches, gazelles and hippos. Credit: Huw Groucutt

The finger bone was discovered in 2016 at the Al Wusta ancient freshwater lake, located in the now extremely arid Nefud Desert, about 340 miles southeast of the Sinai Peninsula. The research team knows little else about the inch-long bone. Whether it belonged to a male or female is yet to be known and the age of the human it belonged to can’t be determined without more evidence.

“Whether this finger bone came from a modern human, I just don’t think that one bone is enough to tell,” cautions John Hawks, an anthropologist at the University of Wisconsin-Madison who was not involved with the study. “So it’s too soon to say that this is the record of modern human dispersal.

“I think it shows clearly that we should be exploring much more in the Arabian peninsula, as there will be more discoveries there.”

The team behind the discovery included researchers from the Max Planck Institute for the Science of Human History, the Saudi Commission for Tourism and National Heritage, the Saudi Geological Survey, King Saud University and the University of Oxford.

Ahmad Bahameem, a member of the Saudi Geological Survey said he was optimistic about future Homo sapiens discoveries from the Arabian Peninsula.

“This fossil is just a piece of a whole skeleton, like a drop of rain,” Mr. Bahameem said. “But the rain is coming,” he added.