Strong Support for Evolution
It probably took less than 10 million yearsthe blink of an eye in geological termsfor the former land mammal to become fully aquatic.
Gradually, the hind legs disappeared, replaced by a powerful tail. Flukes and flippers developed, and swimming style evolved. The sirenian's initial method of swimming probably wasn't too efficient, according to Domning. It essentially kicked backward and upward with its hind legs, like an otter.
About the same time, the ancestors of whales were moving into the water and undergoing the same stages of evolution.
"The fossil record for whales is more complete than for sea cows, but every day the fossil record is getting better," said Domning. "Major gaps are becoming minor gaps, and minor gaps are evaporating."
Only a few weeks ago, researchers reported finding two new species of primitive whales that had well-developed limbs. The fossils were found in Pakistan and reported in the September 21 issue of Science.
The findings should go a long way toward settling the debate between creationism and evolution, said Domning. Creationists claim there is no evidence of macro-evolutionintermediate forms of animals demonstrating the evolution from one kind of animal to another.
"We're finding more and more dramatic evidence by the day that major changes have occurred in both appearance and adaptation," said Domning. "It's no longer a matter of theory. We have actual bones in hand representing all phases of the evolution, from land animal to sea animal, in different groups of animals."
Domning's study, for which the National Geographic Society funded the field work, appears in the October 11 issue of Nature.
Research Supported by the National Geographic Society:
Daryl Domning is one of a distinguished group of scientists from around the globe, in fields ranging from astronomy to zoology, who have been awarded grants from the National Geographic Society's Committee for Research and Exploration (CRE).
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