Since rafting fits the biological evidence, Huber and co-author Jason Ali of the University of the Hong Kong wanted to find out if currents around the island might have changed over time. (Related: "Lemurs Hunted, Eaten Amid Civil Unrest, Group Says.") Lemurs started the migration about 50 million years ago, followed by hedgehog-like tenrecs, then mongoose-like carnivores such as the fossa, and finally rodents 24 million years ago. In addition, genetic evidence suggests Madagascar's mammals arrived in discrete waves spaced several million years apart. "If there was a land bridge between Africa and Madagascar, why didn't large animals like elephants or lions cross?" Huber said. These animals are distantly related to mammals in mainland Africa, and they are all relatively small. One weakness of the land-bridge theory is that today only four major groups of mammals live in Madagascar. "The biologists were right all along," said study team member Matthew Huber, a paleoclimatologist at Indiana's Purdue University. Now, using computer simulations normally employed to study global warming, scientists think the currents might have been more favorable for drifitng to Madagascar 50 million years ago. One of the problems with the rafting theory was that ocean currents and prevailing winds around Madagascar today move east to west-away from, not toward, the island. The ancient refugees were carried to Madagascar by ocean currents, drifting on the open seas for several weeks before finally coming ashore, the model says.īased on genetic and ecosystem evidence, this theory makes more sense than the alternative, which holds that Madagascar's mammals arrived via a land bridge that was later destroyed by shifting continents. The model supports a 70-year-old theory that mainland mammals from southeastern Africa "rafted" to the island on large logs or floating carpets of vegetation after being swept out to sea during storms. (Related: "Three New Lemurs Discovered, Add to Madagascar's Diversity.") Only in the movies could a lion, a zebra, a giraffe, and a hippo wash ashore on Madagascar to start a new life.īut a new computer model suggests there may be a grain of truth in the animated fiction: The ancestors of ring-tailed lemurs, flying foxes, and other mammals that live on the Indian Ocean island got there aboard natural rafts.
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