A fossilized jawbone of what scientists claim is one of the very first humans has been discovered un Ethiopia.
The 2.8 million-year-old specimen is 400,000 years older than researchers thought that our kind first emerged.
The discovery suggests climate change spurred the transition from tree dweller to upright walker.
Prof. Brian Villmoare of the University of Nevada in Las Vegas said the discovery makes a clear link between an iconic 3.2 million-year-old hominin (human-like primate) discovered in the same area in 1974, called “Lucy”.
The fossil record between the time period when Lucy and her kin were alive and the emergence of Homo erectus (with its relatively large brain and humanlike body proportions) two million years ago is sparse.
The 2.8 million-year-old lower jawbone was found in the Ledi-Geraru research area, Afar Regional State, by Ethiopian student Chalachew Seyoum.
The fossil is of the left side of the lower jaw, along with five teeth. The back molar teeth are smaller than those of other hominins living in the area and are one of the features that distinguish humans from more primitive ancestors, according to Prof. William Kimbel, director of Arizona State University’s Institute of Human Origins.
A computer reconstruction of a skull belonging to the species Homo habilis, which has been published in Nature journal, indicates that it may well have been the evolutionary descendant of the species announced today.
The dating of the jawbone might help answer one of the key questions in human evolution. What caused some apes to climb down from the trees and make their homes on the ground.
A separate study in Science hints that a change in climate might have been a factor. An analysis of the fossilized plant and animal life in the area suggests that what had once been lush forest had become dry grassland.
As the trees made way for vast plains, apes found a way of exploiting the new environmental niche, developing bigger brains and becoming less reliant on having big jaws and teeth by using tools.
According to scientists, there were several different species of humans co-existing in Africa around two million years ago with only one of them surviving and eventually evolving into our species, Homo sapiens. It is as if nature was experimenting with different versions of the same evolutionary configuration until one succeeded.
Researchers have discovered that fossils from Northern Kenya show that a new species of human lived two million years ago.
The discovery suggests that at least three distinct species of humans co-existed in Africa.
The research adds to a growing body of evidence that runs counter to the popular perception that there was a linear evolution from monkey to ape to modern human.
The research has been published in the journal Nature.
Anthropologists have discovered three human fossils that are between 1.78 and 1.95 million years old. The specimens are of a face and two jawbones with teeth.
Researchers have discovered that fossils from Northern Kenya show that a new species of human lived two million years ago
The finds back the view that a skull found in 1972 ago is of a separate species of human, known as Homo rudolfensis. The skull was markedly different to any others from that time. It had a relatively large brain and long flat face.
But for 40 years the skull was the only example of the creature and so it was impossible to say for sure whether the individual was an unusual specimen or a member of a new species.
With the discovery of the three new fossils researchers can say with more certainty that H.rudolfensis really was a separate type of human that existed around two million years ago alongside other species of humans.
For a long time the oldest known human ancestor was thought to be a primitive species, dating back 1.8 million years ago called Homo erectus. They had small heads, prominent brows and stood upright.
But 50 years ago, researchers discovered an even older and more primitive species of human called Homo habilis that may have coexisted with H. erectus. Now it seems H. rudolfensis was around too and raises the distinct possibility that many other species of human also existed at the time.
This find is the latest in a growing body of evidence that challenges the view that our species evolved from monkeys in a smooth linear progression. Instead, according to Dr. Meave Leakey of the Turkana Basin Institute in Nairobi, who led the research the find shows that there was a diversity early on in the evolution of our species.
“Our past was a diverse past, our species was evolving in the same way that other species of animals evolved. There was nothing unique about us until we began to make sophisticated stone tools,” she said.
According to Dr. Meave Leakey, the growing body of evidence to suggest that humans evolved in the same way as other animals shows that “evolution really does work”.
“It leads to amazing adaptions and amazing species and we are one of them,” she said.