Madagascar’s Lemurs were Not the First Mammals on the Island

Madagascar’s Lemurs were Not the First Mammals on the Island

Paleontologists of Duke University reveal that Propotto Leakeyi does not belong to a bat.

Fossils carry significant information about the events of the past. Analysis of a fossil can reveal some extraordinary facts. Similarly, they can alter the long-lasting beliefs of the humanity by providing the unknown piece of the puzzle. Such an instance took place recently when the researchers reassessed the African fossils and found that lemurs were not the first to invade the island of Madagascar. In addition to that, the timeframe associated with their colonization is also being challenged following the reexamination of a fossil (Propotto Leakeyi) which is 20 million years old.

Propotto Leakeyi was discovered some 50 years back and has been preserved in a museum storage since then. It was classified as a fruit bat until this latest research which changed things quite dramatically. After a reassessment of the fossil, the researchers declared that it was never a bat. Instead, it is an ancient relative of the ‘Bucktoothed Nocturnal Primate’, which is one of the earliest lemurs known to humanity. According to previous beliefs, lemurs arrived in Madagascar in a single go at around 60 million years ago. Contrary to that, the researchers claim that lemurs arrived in two individual groups and this happened much later than the previous estimates.

The authors of the study argued that both these lineages of lemurs got separated before reaching Madagascar. One of these transformed into the aye-aye while all the other kinds of lemurs came from the other lineage. After this split, both groups colonized Madagascar independently and this took place much later than what is written in the history books. Erik Seiffert, a Professor of Anatomy at the University of Southern California, said,

One implication is that lemurs have had a much less extensive evolutionary history on Madagascar than was previously thought.”

The identity of the fossil didn’t face any objection till 2016 when Gregg Gunnell of the Duke University decided to have a look at the fossil. He observed that the hind teeth of the creature resembled more to a primate than a bat. Likewise, the presence of the stump of a broken front tooth forced him to believe that this fossil came from aye-ayes because they are the only living primates with rodent-like teeth. Gunnell informed Seiffert about his findings. Seiffert acknowledged that by saying,

Gregg wrote to us and said, ‘Tell me I’m crazy.”

An interesting incident with respect to the Propotto Leakeyi took place in 1967, when a paleontologist called George Simpson analyzed the fossil and concluded that it belongs to an unknown member of the Loris family (a type of nocturnal primates having big eyes). However, Alan Walker, one of his colleagues, didn’t feel the same way and convinced Simpson to change his views.

Seiffert worked alongside Steven Heritage of the Duke University who is also a part of the Division of Fossil Primates. They examined 79 genes and 395 anatomical features during their examination which covered 125 mammals, both extinct and living. The results showed that quite a lot of features of the Propotto Leakeyi were similar to the Plesiopithecus, a Buck-toothed Primate which roamed across Egypt some 34 million years ago. It is also an ancient relative of the aye-aye.

The assistance of Doug Boyer, an Associate Professor of Evolutionary Anthropology at the Duke University, proved instrumental in these findings. The researching team generated microCT scans of the lower molars of 42 extinct and living mammal groups in order to compare them with Propotto’s teeth. A computer software was used for this purpose which compared all the pits, ridges, and bumps on the teeth of the animals.

The report published on the 21st August 2018 suggests that a lot of mammals arrived in Madagascar alongside lemurs at that time. That list of mammals includes hedgehog, rodents, tenrecs, and Malagasy Mongooses. Additionally, some reptiles like snakes, frogs, and lizards also reached the island during that time. The researchers proposed that the lemurs might have made the journey across the sea by holding on to tree limbs in a sea storm because these creatures can’t swim. They also mentioned that the lemurs might have to travel shorter distances if we assume that their arrival is more recent. Boyer explained that in the following words:

It’s possible that lemurs weren’t in Madagascar at all until maybe the Miocene. The fossils tell us something we never could have guessed from the DNA evidence about the history of lemurs on Madagascar.”  

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