Fossil gives new insight on cheek-pouch monkeys

A fossilized tooth discovered in the United Arab Emirates suggests that cheek-pouch monkeys appeared up to 3.5 million years before previously thought and provides clues about the evolution of this group of monkeys. 

The first of its kind found outside Africa, the small molar from the left side of the lower jaw, is between 6.5 and 8 million years old. It was discovered by anthropologist Christopher Gilbert of City University of New York and his colleagues, while excavating the Baynunah formation in Abu Dhabi in 2009, and is described in Proceedings of the National Academy of Science¹ .

The Cercopithecine (or cheek-pouch) monkeys, are a subfamily of more than 70 different species, including baboons, macaques, and vervets. Most species are found in sub-Saharan Africa, but macaques are also found throughout southwest Asia and in Gibraltar, making this the most widely distributed group of Old World Monkeys.

Cheek-pouch are believed to have dispersed from Africa during the late Miocene, between 5.3-11.6 million years ago, and this migration could have occurred via three possible routes: over the straits of Gibraltar or Mediterranean basin, across the Arabian peninsula through the Sinai desert to the north, or further south across the straits at Bab el Mandeb. The timing or route of their migration is unknown.

Until this discovery, the earliest cheek-pouch monkey fossils were from macaques, which have been dated between 5-6 million years, so the discovery pushes back the earliest appearance of this group by 2.3–3.5 million years. 

It also suggests that the cheek-pouch monkeys dispersed from Africa to southwest Asia over the Arabian straits of Bab el Mandeb. 

“It’s the first good evidence of cheek-pouch monkey migration along this route,” says Gilbert, “and along with another tooth from Abu Dhabi found 20 years earlier, it strengthens the broader case for Old World monkey migration through the Arabian Peninsula in the Late Miocene.”

“We hope to continue fieldwork in the Baynunah Formation in the near future, looking for more monkey fossils and other mammals as well,” he adds. “Even rare little teeth such as this one can be significant.”

Faysal Bibi of the Abu Dhabi Tourism and Culture Authority, who led the fieldwork, says the study is part of a larger, ongoing project at the Baynunah Formation. “It involved spending weeks at a time in the Abu Dhabi desert, collecting all kinds of fossils, followed by years of analytical and comparative work.” 

“We have an enormous collection, everything from fossil rodents to elephants, that we’re still chipping away at, so the project will continue over the next several years,” he adds.