June 11, 2005

During the spring of 2000, a Pakistani-French team of palaeontologists, led by Jean-Loup Welcomme, was sifting through five tons of sediments in the Bugti Hills of Balochistan, looking for fossils. During the operation, members of the team were extremely surprised when they chanced upon a handful of tiny teeth representing the fossil remains of a mysterious minute primate. These 30 million-year-old teeth are particularly exciting since they represent the fossil remains of an animal for which the living representatives are exclusively found on the remote island of Madagascar — the lemurs. This primate group, cousins to the monkeys and apes, comprises strange creatures, many with fowl-like muzzles and soft, wooly fur. They are characterized by a tooth “comb” jutting from their lower jaw, which is a unique pattern of forward-pointing incisors and canines that they use for grooming or collecting resin on trees.

Modern lemurs consist of about 50 species, ranging in size from a few ounces (like a mouse) to 15 pounds (like a large house cat). Lemurs are tree dwellers with large, bushy tails, but they vary greatly in colour and markings.

The newly found Pakistani primate of about 5 ounces — dubbed Bugtilemur mathesonae (named after Bugtis and also Sylvia Matheson, a famous English ethnologist who greatly contributed towards the understanding of the Bugtis’ traditions) closely resembles Madagascar’s modern dwarf lemur (cheirogales), one of the five living Malagasy families of lemurs. It also resembles its little Malagasy cousin Microcebus — the smallest living primate.

Bugtilemur was probably a nocturnal animal that ate resin, fruits and small insects. Bugtilemur was found from a site seemingly teaming with other aquatic and terrestrial specimens. Fossilized trees, pollen and fruits indicated that Bugtilemur lived in an environment that resembled a modern tropical forest, which has now turned into a vast desert. The discovery of a skeleton of Baluchitherium from the same area testifies to a formerly lush landscape.

Researchers have long studied this group of primitive primates, but their evolutionary history has largely remained veiled, owing to the absence of known fossil representatives. Although recent DNA analyses suggest that these long-tailed, tree-dwelling primates appeared some 60 millions years ago, fossils found from Madagascar date back only 40,000 years, turning their pre-island days into a palaeontological blank slate.

Therefore, Bugtilemur of Pakistan which belongs to Oligocene — the period between 30 and 25 million years from now — represents the only unequivocal evidence of lemurs outside the remote island of Madagascar. The close relationship between Bugtilemur and the modern Malagasy lemur serves to deepen the mystery over when and how lemurs reached Madagascar.

For years, scientists have held that Madagascar was part of a larger land mass, connected to India and Africa (Gondwana). Current geophysical evidence indicates that Madagascar and the subcontinent broke away from each other about 88 million years ago, probably long before the origin of all lemurs.

This suggests that some type of lemur migration across an important water barrier took place after the breakup of the two land masses. However, that scenario presents another puzzle: In which direction was the exodus?

The answer depends on finding out where lemurs evolved first. Because of its proximity and a rich record of primitive primates, early research suggested that Africa was the birthplace of lemurs, although no lemur fossil has been discovered there. It was commonly thought that lemurs later migrated eastwards to Madagascar, perhaps hitching a ride on rafts of floating vegetation to their current giant island home. The discovery of Bugtilemur from Pakistan suggests that this long-held belief needs to be re-examined.

Since this new and exceptional find points towards a possible Asian origin, it makes sense to review our current notions about lemurs and in the process, discover more about their existence.

Research on the subject

In 2001, these findings were published by Dr Marivaux and his colleagues in the acclaimed journal Science. The following section contains extracts of that paper, titled “A fossil lemur from the Oligocene of Pakistan” (October 19, 2001, Volume 294, Pp 587-591):

“Bugtilemur comprises the only unequivocal evidence for lemuriforms outside the remote island of Madagascar at least since the early Oligocene. One of the most enigmatic questions in primate evolution is when and how strepsirrhine lemurs first arrived in Madagascar, and their unexpected presence on the Indian subcontinent provides a greater puzzle. The breakup of Madagascar and Greater India occurred about 88 million years ago (in the middle Late Cretaceous). Even if recent molecular studies infer an initial loris-lemur split at >62 million years ago (Ma) and a lemur radiation at >54 Ma, and more precisely a Middle Eocene age (37.9 to 46.5 Ma) for the lepilemurid, cheirogaleid, indrid, and lemurid clade, the water barrier separating both land masses was already important at that time.

“An earlier time of divergence between the Indian and Malagasy cheirogaleids might be compatible with a possible vicariance hypothesis. Some recent molecular phylogenies assume that primates originated far earlier [around 90 Ma for the origin of primates and 87 Ma for the origin of strepsirrhines] than the fossil record indicates so far (around 55 Ma). In that context, Indian and Malagasy lemurs could be interpreted as derived residues of an ancestral common stock distributed on the Cretaceous Indo-Malagasy block.

“However, the important number of synapomorphies uniting Bugtilemur and the extant Cheirogaleus is not consistent with such an early divergence, and a more recent time of divergence seems alternatively more relevant. In this way, a migration of lemurs should be expected, implying that a dispersal route between Madagascar and the drifting Greater India may have taken place after the breakup.

“Although the geological evidence would tend to negate such a derivation, it has been proposed that terrestrial Malagasy gastropods were able to colonize India during the Tertiary. The Eocene Mascarene and Indian (Chagos-Laccadive) paleoridge systems might have been involved in potential filter or sweepstakes dispersal routes for lemurs. A pertinent question then arises about the direction of that migration, which depends on the geographic location considered wherein strepsirrhine were likely to have originated. Taking into consideration phylogenies, biogeography, and the limited strepsirrhine fossil evidence, an early Paleogene origin for the lemur-loris common ancestor in Africa has been hypothesized. In that frame, two intercontinental migration of lemurs are required: an initial eastwards migration of the African ancestral lemuriform to Madagascar and a subsequent northward migration of an ancestral Malagasy cheirogaleid to India.

“However, the fact that pre-Late Pleistocene continental deposits are virtually nonexistent on Madagascar makes uncertain an old occurrence of lemurs on the island. The same is true for India, where the limited Paleogene fossiliferous localities have so far failed to recover any lemur or loris evidence. Bugtilemur represents the first, notably early, record of lemurs. Although the possibility that India may have been the source of primate colonizers of Madagascar has until recently seemed unlikely, the alternative hypothesis involving an Asian origin for the loris-lemur clade cannot be ruled out in the light of this new discovery. A similar scenario (adapted from molecular data) has been suggested for endemic Malagasy rodents.

The possibility that lemuriforms and lorisiforms originated in Asia rather than in Africa cannot be rejected without further palaeontological evidence from both continents and from Madagascar. The discovery of a cheirogaleid-like lemur in Oligocene deposits of Pakistan suggests that whatever the timing and direction of faunal dispersions, South Asia was, as for anthropoids, an important theater of early strepsirrhine evolution, reflecting the complex role played by the drifting Greater India in the evolutionary history of Malagasy lemurs.”



The writer is a member of the Mission Paleontologique Francaise au Balouchistan (MPFB). He works for the Institute of Evolutionary Science, Montpellier II University, France

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