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Anthropology

Out of Africa

The discovery of two new primate fossils, in Africa and in Asia, supports the theory that Asia, not Africa, was the ancestral homeland of anthropoid primates.

Elucidating the origins of anthropoid primates (the group humans, apes, and monkeys belong to) and their relationship to earlier and more primitive primates known as prosimians (the ancestors of lemurs and tarsiers) has lately been a major area of interest in paleoanthropology. Until a decade ago, most paleontologists believed anthropoid primates originated in Africa, where the first fossils were found. Yet the recent discovery of specimens in other parts of the world–47 million year-old remnants were found in China, and later specimens in Thailand, Pakistan, and Myanmar (also known as Burma)–sowed doubts on their geographical origins.
Now, the hypothesis of an Asian birthplace is further supported by two recent discoveries made in Africa and in Asia by scientists including researchers from CNRS' ISEM in Montpellier.1
out of africa

© L. Marivaux/CNRS

Fossil excavation site of Ganle, a small village in Myanmar.



Until now, the Algeripithecus primate, of which two fossilized teeth were discovered in 1992 in the Algerian Sahara, was considered to be the most ancient anthropoid, approximately 50 million years old. “Its teeth were very similar to those of Egyptian fossils that are more complete and unmistakable remnants of anthropoid primates,” says CNRS researcher Rodolphe Tabuce. “So by extension, researchers assumed Algeripithecus was an anthropoid too.” Nevertheless, much controversy surrounded this assumption.
The excavation of additional jaw and skull fossils on the Algerian site suggests Algeripithecus was in fact not an anthropoid but a prosimian.2 Fragments of a mandible display characteristics typical of lemur-like ancestors, like the presence of a dental comb, used to clean the animal's fur. “Anthropoids did not have dental combs, but prosimians did,” specifies Tabuce. Similarly, pieces of a skull suggest cranial nerve routes similar to those found in prosimians. “By eliminating the Algeripithecus, the Egyptian specimens become the oldest African anthropoid fossils, dating back 30-37 million years,” explains Tabuce.
The same team has made yet another discovery that further supports the theory of an Asian birthplace. In Myanmar (Asia), they excavated a 37 million-year-old fossil–thus older than the Egyptian fossils.3 The specimen is the second oldest fossil found in Asia, and corresponds to fragments of the lower jawbone and teeth of a new species of primates–Ganlea megacanina– named after their greatly enlarged lower canine. The jawbone's morphology and marks found on the remaining teeth suggest feeding characteristics common to some modern monkeys (Saki, Titi...), which nowadays use their canines to crack open tropical fruit to extract the nutritive seeds. “This behavior is only found in monkeys and has never been documented among extinct or existing prosimians,” notes CNRS researcher Laurent Marivaux. “Ganlea looks and acts like an anthropoid, not a prosimian,” he says. “These two complementary findings provide strong support to the hypothesis that anthropoid primates originated in Asia and could have later spread to Africa.”

Clémentine Wallace

Notes :

1. Institut des Sciences de l'Evolution (CNRS / Université Montpellier-II).
2. R. Tabuce et al., “Anthropoid vs. strepsirhine status of the African Eocene primates Algeripithecus and Azibius: craniodental evidence,” Proc. Biol. Sci., 2009. [Epub ahead of print].
3. K.C. Beard et al., “A new primate from the Eocene Pondaung Formation of Myanmar and the monophyly of Burmese amphipithecids,” Proc. Biol. Sci., 2009. 276: 3285-94.

Contacts :

ISEM, Montpellier.
Laurent Marivaux,
Laurent.Marivaux@univ-montp2.fr
Rodolphe Tabuce,
rodolphe.tabuce@univ-montp2.fr


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