Evolution

The Evolution of Lemurs



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Lemurs are fascinating species which come in a variety of forms. Their large eyes and mysterious natures have earned them a name which, in Latin, means 'ghost'

There are currently as many as 49 different species cataloged. The number of species listed goes up periodically as Malagasy scientists study the DNA profiles of the ones already discovered.

Lemurs only exist on Madagascar and the Cormoro Islands nearby. They are amongst the most endangered species on the planet because of this. They are predominantly forest dwellers and are being very badly impacted by human activities like commercial logging which has drastically reduced their habitat. This is a serious matter, as lemurs are not the only species to exist solely on Madagascar.

Like Galapagos, study of Madagascar provides us with a wealth of information about the ways in which evolution works. In the case of lemurs adding fascinating insights into our own genetic heritage.

Like monkeys, apes and humans, lemurs are primates. We all share a common ancestor. They can only be considered very distant cousins to us though. If we go back to around 63 million years ago, there were two families of primates: the haplorhines or 'simple noses', to which we belong; and the strepsirhine or 'split noses', to which lemurs belong. They are considered the closest set of species to ancient 'pro-simians', the antecedent to actual simians, or monkeys.

Pro-simians dominated the primate scene before anthropoids came along, fossils have been found on most continents. Once anthropoids gained a foothold, in most cases they out-competed the pro-simians so that most of the ancient species died out. Other surviving pro-simians include African bushbabies and tarsiers in Borneo. The lemurs particular line branched off from the rest about 55 million years ago.

The story of evolution, as told by the fossil records, has always been heavily influenced by changes in the arrangement of the Earth's landmasses along with climate. One of the most noticeable features is 'adaptive radiation'. Like a tree sending out branches into cleared space, species will proliferate and diversify whenever they find themselves in a scenario where there is no competition. This is what happened with lemurs in Madagascar.

Until about 165 million years ago, there were only two great landmasses on planet Earth. Laurasia in the north and Gondwanaland in the south. Madagascar split off from Gondwanaland about that time.

55 million years ago, our early pro-simian cousins somehow managed to find their way over the ocean to Madasgascar. The commonly used term for this kind of migration is 'rafting' because it is thought that animals probably floated on logs or matted vegetation. The little primates found themselves marooned. There were no other primates of any kind there when the arrived and during the ensuing millenia they were able to radiate into the empty niches.

Around 2000 years ago, humans arrived on the islands and began to have an impact. Some species which were around then haven't survived. For example, there was once a large ape-sized lemur called Archaeoindris, which must have weighed around 400lb. One theory is that they were hunted to extinction, along with most of the other larger species of animals. Other large species of lemur that died out include the Megaladapis, which was the size of an orangutan, and the giant 'sloth' lemurs. Today the sizes range between that of a small mouse, and a cat.

The conservation of Madagascar should be of the utmost importance to us because it is a cradle of genetic diversity. Lemurs form a unique branch of our own family tree and we still have a lot to learn from them.



Sources:

Lemurs.us

Dr. Kenneth E. Glander, Director of the Duke University Primate Center

Richard Dawkins 'The Ancestors Tale'

BBC news.com 'New lemurs found in Madagascar'

Dr. Laurie Godfrey, University of Massachusetts

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