A team of U.S. and Ethiopian scientists has discovered the fossilized remains of what it believes is humankind's oldest walking ancestor.

The scientists say the bones, discovered in northeastern Ethiopia, are between 3.8 and four million years old.

That would make the fossil older than the famous skeleton, named "Lucy," which is 3.2 million years old.

The co-leader of the discovery team, U.S. Scientist Bruce Latimer, told journalists in the Ethiopian capital, Addis Ababa, Saturday, the new fossils include a complete tibia from the lower part of the leg, ribs, vertebrae, and a pelvis.

He said there is also an ankle bone which, with the tibia, proves the creature walked upright.

The scientists say the discovery will help them better understand how early humans first began to walk on two feet.

Some information for this report provided by AFP and AP.