Single tooth tells a whole story about pre-historic Arabia

Scientists sifting through material on Shuwaihat Island in Abu Dhabi, looking for fossils. Courtesy Dr Faysal Bibi.

It is easy to imagine the excitement scientists feel when they discover the fossilised skeleton of a long-extinct animal.

Teasing out the bones, the skull and the teeth, and explaining their significance, is the most rewarding experience palaeontologists can have.

Yet complete finds are rare indeed. It is fortunate, then, that even more modest finds can be sources of wonder, whether they are a partial skeleton, a skull or a jawbone with teeth. Or perhaps, even if they are just a single tooth.

Just such a lone fossilised tooth was enough to excite a group of scientists sieving sand back in 2009, hoping for interesting material from the seven-million-year-old Baynunah Formation in Abu Dhabi’s Al Gharbia region.

“When we found it, we were jumping around on the hill where we were doing this back-breaking sieving work,” said Dr Faysal Bibi, of Berlin’s Natural History Museum, a member of the team that made the discovery.

“There’s a sense of surprise and wonder that never goes away with every new discovery.”

The cheek tooth belonged to what is the earliest discovered member, and the only one found outside Africa, of a monkey tribe called the Cercopithecini, a type of “old world” monkey whose present-day representatives includes guenons, which mostly live in forests.

The find was introduced to the scientific community late last year at a meeting of the Society of Vertebrate Palaeontology, but a paper describing it more fully is currently being reviewed. Until publication, the scientists emphasise their conclusions are only preliminary.

It is only the second piece of evidence that monkeys lived in Arabia about seven million years ago. The other, a canine tooth from a male old world monkey, was discovered in 1989 at Jebel Dhanna, about 250 kilometres west of Abu Dhabi city.

Turn the clock back 7 million years, and what is now a searingly hot desert area with little rainfall was very different. It was much greener and home to large animals such as antelopes, crocodiles, elephants, giraffes, hippopotamuses and ostriches.

The discovery of the Baynunah monkey indicates that animals that originated in Africa were inhabiting an area from which they could have travelled into Eurasia, providing further evidence that South-West Asia was a staging post for this movement. Other animals believed to have used the same route include apes and members of the elephant family.

And its age appears to bury the idea that this type of cercopithecin monkey may have arisen less than five million years ago.

It might seem remarkable that a single tooth can support these conclusions but a fossilised tooth can tell researchers more than might be thought.

“Sometimes the information [from a fossil] is very low quality. You might only be able to say it’s part of a bone of a mammal of large size, because you don’t have enough information to pinpoint whether it’s an elephant or rhino or horse,” said Dr Bibi.

“But generally palaeontologists like teeth because they evolve in a distinctive way among species. Sometimes … an elephant or rhino or horse you can tell apart with just a few millimetres of a tooth. If you have a full tooth, you might be able to say what kind of horse it is, or in this case, what kind of monkey.”

Finding a tooth, or a fragment of one, only comes after many hours of sieving through hundreds of kilograms of sand. The scientists who found the monkey tooth had special sieves made with gaps of 1mm, meaning they could capture everything down to even a rodent tooth. In the event, none of that was needed – the fossil monkey tooth was spotted in the sand by an sharp-eyed researcher.

It was found on Shuwaihat Island, part of an area of interest to palaeontologists that is 20km long and stretching from as much as 60km inland.

Finds in the area have ranged from fish parts to lizard, snake and rodent fossils. Much of it is yet to be published – indeed, many of the finds have yet to be properly studied. That’s not unusual, according to Dr Mark Beech, cultural landscapes manager in the Historic Environment Department at Abu Dhabi Tourism and Culture Authority and one of the other researchers on the team.

“It’s a lot of work behind the science, which is often the case when you’re dealing with vertebrate palaeontology… sometimes it’s five to 10 years later when you actually publish the fossil you’ve discovered,” said Dr Beech.

For any given find, scientists may have to make precise measurements, take photographs, and even visit other museums to compare the new discovery with other specimens like it.

“It’s not a straightforward and easy thing to do. It’s a long, careful process and papers are very painstaking endeavours because you’re dealing with detailed taxonomy, detailed morphology and detailed analysis of your fossils and other known beasts from other sites.”

That this tooth is only the second piece of evidence that monkeys were living in Arabia about 7 million years ago reflects the relative paucity of knowledge about the region. That only makes it all the more exciting for the researchers.

“Because not much is known in the Arabian Peninsula in general, we’re pretty much recording something new and something new for the whole subcontinent,” said Dr Bibi. “There’s very little known – for us as scientists, that’s an advantage.”

One thing that is especially interesting about the monkey is its age. The earliest human ancestors are from Chad around 6 million years ago. The monkey fossil is approaching that time.

“We’re getting close to the ballpark figure of the time period when you have the emergence of the earliest human ancestors,” said Dr Beech.

It raises intriguing prospects about what other fossils might be out there to find. But for now, what is the only fossil monkey of its kind outside Africa is providing fascination enough for researchers.