3.6-Million-Year-Old Fossil Expands Human Family Tree

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WASHINGTON -- Scientists may have found the great, great, great, etc., grandfather of the famous fossil Lucy.

A new partial skeleton of an early hominid known as Australopithecus afarensis was discovered in a mud flat of the Afar region of Ethiopia.

Dated about 3.6 million years ago, the find is about 400,000 years older than the famous Lucy, which was among the earliest upright walking hominids, researchers report in Tuesday's edition of Proceedings of the National Academy of Sciences.

The bones indicate this ancestor also walked upright, but was considerably larger than Lucy, who stood about 3.5 feet tall. Because of his size -- he would have stood more than 5 feet tall -- the new specimen has been named "Kadanuumuu," which means "big man" in the Afar language.

"This individual was fully bipedal and had the ability to walk almost like modern humans," said lead author Yohannes Haile-Selassie of the Cleveland Museum of Natural History.

"As a result of this discovery, we can now confidently say that Lucy and her relatives were almost as proficient as we are walking on two legs, and that the elongation of our legs came earlier in our evolution than previously thought," he said in a statement.

Australopithecus afarensis is the best-known direct early human ancestor. Until now, the only partial skeleton assigned to this species was Lucy, the 3.2 million-year-old female discovered in 1974 by a team led by then Museum curator Dr. Donald Johanson.

"Ardi," or Ardipithecus ramidus is a 4.4 million-year-old hominid species unveiled in October 2009 by a team that included Haile-Selassie, Lovejoy, and Museum scientists and associate researchers Dr. Linda Spurlock, Dr. Bruce Latimer and Dr. Scott Simpson. "Ardi" was named by the journal Science as breakthrough discovery of the year.

The find was made by an international team led by Haile-Selassie and Owen Lovejoy of the Cleveland museum. The research was funded by the National Science Foundation, the Leakey Foundation, the Wenner-Gren Foundation and the National Geographic Society.