Why Do Lemurs Live Only in Madagascar?

One hundred and sixty million years ago, Madagascar was attached to the African mainland as a part of a supercontinent that consisted of today's Africa, South America, Australia, Antarctica, India and Madagascar. Lemurs already may have been on Madagascar when it separated from the African continent. But a more plausible theory suggests that because Madagascar separated from Africa by hundreds of kilometers before the evolution of lemurs, these primates crossed over from Africa by floating on large bunches of vegetation. Once they settled on the island, they became reproductively isolated and free from the threat of other primates. In fact, the only reason they still survive there today is because of Madagascar's isolation.

Competing primates like monkeys and apes never made it to Madagascar. So the lemurs that floated over to the island thrived — competing only among themselves for the best food sources — and wound up evolving into many different species. The lemurs that didn't escape to the island met a very different fate. African lemurs became extinct when they couldn't compete with other primates for food, and the same thing happened elsewhere around the world. A 30-million-year-old fossil of a modern dwarf lemur, Cheirogaleus, was found in central Pakistan, for example [source: National Geographic News]. But no such animal exists in that part of the world today.

­This isolation from other primates ended, however, when the first human settlers arrived on the island from Malaysia and Indonesia about 2,000 years ago. The arrival of humans wreaked havoc on the lemur populatio­n. The larger species of lemur suffered the most. Viewing large, fearsome looking, gorilla-sized lemurs as threats, humans hunted them. Today, the largest lemur, the Indri, is tiny in comparison to the over-sized lemurs that once inhabited Madagascar. The Indri weighs only 15 to 20 pounds (6.8 to 9 kilograms). But fossil records indicate that the largest extinct lemur species, Archaeoindris, weighed between 350 and 440 pounds (158 to 199 kilograms) [source: PBS]. By the time Europeans arrived to Madagascar in the 1500s, 15 species of lemurs had already become extinct. Today, all lemurs are endangered species. Humans not only have hunted lemurs but have also destroyed their habitats through deforestation.

Lemurs continue to live in almost all of Madagascar's ecosystems and terrains, and they range in size from the 25-gram pygmy mouse lemur to the 15- to 20-pound (6- to 9-kilogram) Indri [source: Smithsonian National Zoo].

Today there are 88 species of lemurs living in Madagascar [source: Smithsonian National Zoo]. Researchers believe that 10 to 20 previously undiscovered species may be found in the next generation [source: Wild Madagascar]. Lemurs are also found on the nearby Comoros islands; it's generally believed that they were introduced to the area by humans.

Twenty-one percent of all primate genera, the taxonomic groups above species, and 36 percent of all primate families, the taxonomic groups above genus, live in Madagascar. That makes the island a target for preserving and protecting the primates for research. Despite their ecological importance, humans have steadily contributed to the destruction of primate habitats. Eighty percent of the island's forests have been destroyed, mostly for logging or crop cultivation purposes.

­Due to Madagascar's economic constraints — the average per capita income is equal to about $200 — and large  of over 14 million people, subsistence for humans outweighs preservation. However, efforts are being made to preserve the lemur and the island's biological diversity, or variation of life forms, in a way that can also help Madagascar's people. Madagascar's diverse geography, which contributes to the variance of the life forms living there, is one of the most unique in the world. Due to both its beautiful landscape and varied animal and plant population, ecotourism has become an increasingly popular industry in Madagascar. It may be the a key to preserving this primate on the verge of extinction [source: Wild Madagascar].

We can also learn much about our own primate pasts from the lemur. Lemurs are less closely related to humans than monkeys and apes. They more closely resemble the primates that existed tens of millions of years ago. Even so, by studying lemur development, researchers might be able to find out more about the human evolutionary process [source: Smithsonian National Zoo].