Discovery of a middle finger bone in Arabia changes human history
Even for a desert, the Nefud is nearly bone-dry. Only about an inch of water falls onto the red, sandy soil in northern Saudi Arabia over the course of a year.
But 85,000 years ago, hippos roamed the Nefud.
At that time, heavy, monsoonal downpours filled thousands of lakes in the region. Rivers and streams criss-crossed the land. Leaping gazelles and wild cattle munched on the grasslands.
And it appears that an early group of humans followed these African animals to this once-hospitable land.
Archaeologists spent a decade sifting through the sands in this now dry and grossly understudied region of the world.
Among a rich collection of primitive tools and animals bones found there, the researchers discovered a single bone from a modern human’s middle finger. The 90,000-year-old specimen, an inch and quarter in length (3.2 centimeters), is now the oldest-known human fossil outside of Africa and The Levant (the biblical area around the eastern Mediterranean, which includes modern-day Israel and Jordan).
New research detailing that discovery, published Monday in the journal Nature Ecology and Evolution, alters our understanding of a seminal time in human history: when we left Africa and eventually spread out across the globe.
Near the team’s dig site called Al Wusta, east of the Red Sea, the team had previously located many archaeologically-intriguing places filled with animal bones.
“One thing was always missing,” Huw Groucutt, an archaeologist at the University of Oxford’s Institute of Archaeology and lead author of the study, told reporters in a call last week.
“Ancient human fossils,” he said.
Humans became a completely unique species around 200,000 years ago, in Africa. Eventually, we began to leave.
The widely-accepted theory of human expansion out of Africa held that there was a first major movement into The Levant some 130,000 years ago (but perhaps earlier). Here, we inhabited places like caves in present-day Israel. Later, some 60,000 years ago, there is thought to have been a second major human dispersal out of Africa.
But with the discovery of this middle finger fossil, the study’s authors argue that we probably moved out of Africa many times.
This single fossil puts us in Arabia around 85,000 years ago, some 20,000 years earlier than previously thought.
These remarkable journeys by foot, then, “were far more complicated than our textbooks tell us,” Michael Petraglia, an archaeologist at the Max Planck Institute for the Science of Human History and study co-author, told reporters last week.
“The argument is that Homo sapiens got to The Levant and stayed there for long periods of time and never moved geographically anywhere else,” Petraglia said, referring the first major movement north. “And our findings shows that to be a false proposition.”
“Homo sapiens made it far wider geographically than just being in The Levant itself.”
The discovery will likely encourage more archaeologists to journey into the hyper-arid Nefud desert, and beyond.
“I think this is a cool discovery and it definitely suggests that we need to explore the Arabian peninsula much more for fossil humans and their ancestors,” John Hawks, an anthropologist at the University of Wisconsin–Madison, who was not involved in the study, said via email.
But while this middle finger bone certainly improves our understanding of early human history, anthropologists point out that it doesn’t radically overhaul our past. We knew humans were migrating in this general time period — we just don’t fully understand how or where.
“It is evolutionary — but not revolutionary,” Ellen Miller, a biological anthropologist at Wake Forest University who was not part of the study, said in an interview. “It doesn’t make us rewrite history, but it is another piece in the puzzle.”
Hippo bones helped fill in the story
A major reason why the archaeologists traveled to the remote Nefud desert is because scientists had previously found a rich collection of dried-up lakes and animal bones there — notably from large fauna like hippos. And where there are hippos, there is plentiful vegetation and water.
“It’s wet enough that you would think it would have a carrying capacity for hominids,” said Trenton Holliday, chair of the Department of Anthropology at Tulane University who played no part in the research.
Additionally, having animal bones gave the researchers a significantly more confident idea about the time humans were inhabiting this once humid, lake-filled woodland.
The archaeologists could date the actual bone, the animal bones nearby (such as a hippopotamus tooth), and the soil the bones were found in to date the fossil.
“The ages all agree,” said Groucutt.
How do we know it’s a finger bone from a modern human?
Identifying a single finger bone as belonging to a modern human is not always a simple task, according to Holliday.
However, that doesn’t mean it’s impossible to figure it out.
Although our evolutionary hominid cousins, like Neanderthals, have similar hands, biological anthropologists can pick out a Homo sapiens‘ bone with near absolute certainty. Scientists can directly compare a bone like this to the fossils of other hominids, and see a distinct difference.
For example, Holliday noted that earlier hominids tend to have broader middle finger bones than humans.
“It’s a modern human,” said Holliday, adding that he could tell that it was a modern human from images of the bone and reading the measurements.
The bone, though around 85,000 years old, is nearly indistinguishable from that of a human alive in 2018.
“If you stuck it into a burial today, nobody would blink,” Holliday said.
The study’s authors are confident it’s a middle finger bone but, it should be noted, they do concede that it may belong to another similar finger, like the index finger.
The research team spent over a year scrutinizing this particular bone. The now-famous bone traveled the globe, going to Australia for dating analysis and being sent to the University of Cambridge in the United Kingdom before landing at its current resting spot, in Germany. At Cambridge, researchers used a technique called tomography to peer inside the bone, which involves using a large X-ray machine to scan its internal structure.
“These studies very strongly demonstrated that this finger bone belongs to a member of our species,” said Oxford’s Groucutt.
That said, it’s still just one fossil.
Why weren’t more human bones found?
“It is odd that we found only one fossil,” said Groucutt. “But it’s very rare for things to fossilize,” he said, noting that anything dead has to be buried quickly. And even if that occurs, a whole host of things have to go right for a bone to be naturally preserved.
“The rest of the body must have just weathered away,” he said.
But there certainly may be other modern human fossils lying around. Generally, the Arabian Peninsula hasn’t been studied too well compared to other regions in the world.
“Really, there are large chunks of the world that are unexplored,” said Petraglia. Arabia has few active archaeological sites like Al Wusta, “but places like Europe are absolutely crowded with dozens of teams that have been working for decades,” he said.
“We have huge biases in our knowledge about what’s going on in certain parts of the world,” said Petraglia.
For this reason, today’s highly-valued middle finger could very well be overshadowed by another, older bone, found somewhere else under the harsh Arabian sun. And with it, our understanding of early human history will again be altered.
“It’s the earliest for now,” said Holliday. “Until we find the next thing.”