The 88,000-year-old finger bone that rewrites mankind's history: Human fossil found in Saudi Arabia suggests our ancestors spread out of Africa 20,000 years earlier than first thought

  • The three centimetre (1.25 inch) long middle finger was found in the desert
  • It is the oldest directly dated Homo sapien fossil discovered outside of Africa
  • The bone was scanned in three dimensions and confirmed to be modern human 
  • The first homo sapiens may have entered Arabia by crossing the Red Sea

The story of mankind's early history may have to be rewritten, thanks to a fossilised finger bone from an early modern human dating back around 88,000 years.

Experts found the remains in the deserts of Saudi Arabia, suggesting that early migration out of Africa into Eurasia was more expansive than previously thought.

It is the oldest directly dated Homo sapien fossil outside of the continent or the Levant, the area around what is now Israel, Palestine and the Lebanon.

The three centimetre (1.25 inch) long middle finger is around 20,000 years older than the date from which modern humans were thought to have left Africa.

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The fossil is a finger bone and was unearthed at Al Wusta, in what is now Saudi Arabia. The authors conducted radiometric dating on the bone and determined that the finger is at least 85,000 years old

The fossil is a finger bone and was unearthed at Al Wusta, in what is now Saudi Arabia. The authors conducted radiometric dating on the bone and determined that the finger is at least 85,000 years old

 

Using a technique called uranium series dating, a laser was used to make microscopic holes in the fossil and measure the ratio between tiny traces of radioactive elements. This discovery shows that early members of our species were not just restricted to the Levant

Scientists from the Max Planck Institute for the Science of Human History made the discovery at Al Wusta, an ancient fresh-water lake located in what is now the hyper-arid Nefud Desert.

Numerous animal fossils, including those of hippopotamus and tiny fresh water snails were found at the site, as well as abundant stone tools made by humans. 

Among these finds was the well preserved and small fossil, which was immediately recognized as a human finger bone.

The bone was scanned in three dimensions and its shape compared to various other finger bones, both of recent Homo sapiens individuals, from other species of primates and other forms of early humans, such as Neanderthals. 

The results conclusively showed that the finger bone, the first ancient human fossil found in Arabia, belonged to our own species. 

Lead author Dr. Huw Groucutt, of the University of Oxford said: ‘This discovery for the first time conclusively shows that early members of our species colonised an expansive region of southwest Asia and were not just restricted to the Levant.

At the time the finger was buried, the climate of the region around Al Wusta was humid and monsoonal. Today it is vastly different and is covered in sand. 

At the time the finger was buried, the climate of the region around Al Wusta was humid and monsoonal. Today it is vastly different and is covered in sand. 

‘The ability of these early people to widely colonize this region casts doubt on long held views that early dispersals out of Africa were localised and unsuccessful. 

'This finger bone from Al Wusta suggests homo sapiens is moving out of Africa far earlier than 65,000 years ago, it’s 20,000 years earlier than expected.’

While homo sapiens bones dated to 177,000 years ago have been found in a cave in Israel, evidence is scant for any further expansion anywhere beyond the coasts. 

The research suggests that the first homo sapiens may have entered Arabia by crossing the Red Sea at a time when it was ‘little more than a river’.

Experts used a technique called uranium series dating to make the discovery. 

A laser was used to make microscopic holes in the fossil and measure the ratio between tiny traces of radioactive elements. These ratios revealed that the fossil was 88,000 years old. 

Other dates obtained from associated animals fossils and sediments converged to a date of approximately 90,000 years ago. 

WHAT DO WE KNOW ABOUT HUMANKIND'S JOURNEY OUT OF AFRICA?

The traditional view

The traditional 'Out of Africa' model suggests that modern humans evolved in Africa and then left in a single wave around 60,000 years ago. 

The model often holds once modern humans left the continent, a brief period of interbreeding with Neanderthals occurred.

This explains why individuals of European and Asian heritage today still have ancient human DNA.

There are many theories as to what drove the downfall of the Neanderthals.

Experts have suggested that early humans may have carried tropical diseases with them from Africa that wiped out their ape-like cousins.

Others claim that plummeting temperatures due to climate change wiped out the Neanderthals.

The predominant theory is that early humans killed off the Neanderthal through competition for food and habitat.

How the story is changing in light of new research

Recent findings suggest that the 'Out of Africa' theory does not tell the full story of our ancestors.

Instead, multiple, smaller movements of humans out of Africa beginning 120,000 years ago were then followed by a major migration 60,000 years ago.

Most of our DNA is made up of this latter group, but the earlier migrations, also known as 'dispersals', are still evident.

This explains recent studies of early human remains which have been found in the far reaches of Asia dating back further than 60,000 years.

For example, H. sapiens remains have been found at multiple sites in southern and central China that have been dated to between 70,000 and 120,000 years ago.

Other recent finds show that modern humans reached Southeast Asia and Australia prior to 60,000 years ago.

Based on these studies, humans could not have come in a single wave from Africa around this time, studies have found. 

Instead, the origin of man suggests that modern humans developed in multiple regions around the world.

The theory claims that groups of a pre-human ancestors made their way out of Africa and spread across parts of Europe and the Middle East.

From here the species developed into modern humans in several places at once. 

The argument is by a new analysis of a 260,000-year-old skull found in Dali County in China's Shaanxi Province.

The skull suggests that early humans migrated to Asia, where they evolved modern human traits and then moved back to Africa. 

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Further environmental analyses also revealed the site to have been a freshwater lake in an ancient grassland environment far removed from today's deserts.

Prior to this discovery, it was thought that early dispersals into Eurasia were unsuccessful and remained restricted to the Mediterranean forests of the Levant, on the doorstep of Africa 

The fossilised finger demonstrates that rather than just clinging to the coastline as they left Africa, they ventured into the interior of what is now Arabia.

At this time, Arabia was humid and monsoonal crossed with rivers and dotted with hundreds of lakes. 

These old watering holes – long since having dried up – are expected to reveal many more insights as the region has not been extensively explored by archaeologists. 

For the Al Wusta (pictured) finger bone, the authors were also able to corroborate the dates from surrounding animal remains and sediments using electron spin resonance and optically stimulated luminescence techniques 

For the Al Wusta (pictured) finger bone, the authors were also able to corroborate the dates from surrounding animal remains and sediments using electron spin resonance and optically stimulated luminescence techniques 

Professor Michael Petraglia of the Max Planck Institute for the Science of Human History added: ‘The Arabian Peninsula has long been considered to be far from the main stage of human evolution.

‘This discovery firmly puts Arabia on the map as a key region for understanding our origins and expansion to the rest of the world. As fieldwork carries on, we continue to make remarkable discoveries in Saudi Arabia’.

Donald Henry, professor of Anthropology at Tulsa University said in a commentary that the findings lend support that homo sapiens did not just fan out across the Levant – but also across the Red Sea.

WHAT IS URANIUM-THORIUM DATING?

Uranium-Thorium dating is a way of determining the age of a rock by the amount of radioactive Thorium it contains.

This method can be used to determine the age of calcium carbonate materials, such as coral. 

Scientists can measure the amount of Thorium-230 in a sample of rock, if the rock contained Uranium originally. 

Uranium is often found in trace amounts in certain types of rock and is radioactive.

It has a half-life (the amount of time it takes for the elements radioactivity to decrease by half) of about 245,000 years.

At this point it undergoes alpha decay (it releases an alpha particle, which is also the same as the nucleus of a Helium atom) and forms Thorium-230.

Thorium has a much shorter half-life of 75,000 years. 

Unlike other types of radioactive dating, Uranium-Thorium (U-Th) dating doesn't reach a stable end point.

Instead, the decay of Thorium and the production of Thorium reach a form of balance - called secular equilibrium. 

Uranium-Thorium dating is a method can be used to determine the age of calcium carbonate materials, such as coral

Uranium-Thorium dating is a method can be used to determine the age of calcium carbonate materials, such as coral

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He said: ‘The most likely access to Arabia from Africa is near the southern end of the Red Sea over the narrow Bab el Mandeb strait. 

‘Interestingly, during many intervals of the Late Pleistocene, lower sea levels would not only have narrowed the crossing to little more than a large river, they also would have exposed extensive areas of a shallow shelf, creating a fertile, lowland zone attractive to colonization by plants, animals and humans.’

The full findings of the study were published in the journal Nature Ecology and Evolution.

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