Washington:
Scientists have discovered the skeleton of a human ancestor - dating back 1.34 million years - characterized by a "robust" jaw and skull bones and a gorilla-like upper body.
The muscular creature was more adaptive to its environment than previously thought, scientists say.
Researchers found a partial skeleton - including arm, hand, leg and foot fragments - dated to 1.34 million years old and belonging to Paranthropus boisei at the Olduvai Gorge World Heritage fossil site in Tanzania.
The find represents one of the most recent occurrences of P boisei before its extinction in East Africa.
"This is the first time we've found bones that suggest that this creature was more ruggedly built - combining terrestrial bipedal locomotion and some arboreal behaviors - than we'd previously thought," said Charles Musiba, associate professor of anthropology at the University of Colorado.
"It seems to have more well-formed forearm muscles that were used for climbing, fine-manipulation and all sorts of behavior," said Musiba.
While P boisei was known for its massive jaws and cranium, the build and skeletal adaptations of the rest of the archaic hominin's body have been unknown until recently.
During excavations at Olduvai in 2010-2011, the team discovered the partial skeleton of a large adult individual who is represented by various teeth and skeletal parts.
P boisei was a long-lived species of archaic hominin that first evolved in East Africa about 2.3 million years ago.
In the absence of evidence of other skeletal remains, it was commonly assumed that the skeleton of P boisei was like that of more ancient species of the genus Australopithecus, from which P boisei likely evolved.
The size of the arm bones suggests strong forearms and a powerful upper body.
"It's a different branch on our ancestry tree. It came later than the other hominins, so the question now is 'what happened to it?" said Musiba.
He noted that the creature likely stood 3.5 to 4.5 feet tall and possessed a robust frame.
"We know that it was very strong. It's unprecedented to find how strong this individual was. The stronger you are the more adaptive you are," Musiba said.
The study was published in the journal PLOS ONE.