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It may take 10m generations for cats to evolve as big as elephants

Washington, Tue, 31 Jan 2012 ANI

Washington, Jan 31 (ANI): An international team of researchers exploring mammal size after dinosaurs became extinct 65 million years ago has found that it took about 10 million generations for terrestrial mammals to hit their maximum mass: that's about the size of a cat evolving into the size of an elephant.


Sea mammals, such as whales took about half the number of generations to hit their maximum.


But the team discovered it took only about one hundred thousand generations for very large decreases, such as extreme dwarfism, to occur.


"Our research demonstrates, for the first time, a large-scale history of mammal life in terms of the pace of growth. This is significant because most research focuses on microevolution, which are changes that occur within a specific species," said Dr. Jessica Theodor, co-author of the study and an associate professor of biology at the University of Calgary.


The research team looked at 28 different types of mammals from the four largest continents (Africa, Eurasia, and North and South America) and all ocean basins for during the last 70 million years.


The researchers were surprised to learn how quickly body-size decreased: the rate is more than 10 times faster than the increases.


"Many of the species which shrunk, such as the dwarf mammoth, dwarf hippo and dwarf hominids, found in the Indonesian island of Flores, became extinct," said Theodor.


"What caused their dwarfism? They may have needed to be small to survive in their environment or perhaps food was scarce and a small stature would require less nutrients," added Theodor.


This research will help scientists to better understand mammal evolution: what conditions allow a certain mammals to thrive and grow bigger and what conditions would slow the pace of growth and potentially contribute to extinction.


The study was published in the journal Proceedings of the National Academy of Sciences. (ANI)


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