Oldest human bone fossils found buried in the rocks

Fossil hunters have found a lower jaw bone and five teeth which have been described as the oldest remains ever found belonging to the genus Homo; the lineage that ultimately led to modern humans, on a hillside in Ethiopia.

The jaw was spotted poking out of a rocky slope at the Ledi-Geraru site in the dry and dusty Afar region of the country about 250 miles from Addis Ababa, The Guardian UK reports.

The US-led research team believes the individual lived about 2.8 million years ago, when the now parched landscape was open grassland and shrubs nourished by tree-lined rivers and wetlands.

The remains are estimated as being about 400,000 years older than fossils which had previously held the record as the earliest known specimens on the Homo lineage.

The new fossil has a handful of primitive features in common with an ancient forerunner of modern humans called Australopithecus afarensis, but with more modern traits too. Some are seen only on the Homo lineage, such as a shallower chin bone.

The discovery sheds light on a profoundly important but poorly understood period in human evolution that played out between two and three million years ago, when humans began the crucial transformation from ape-like animals into forms that used tools and eventually began to resemble modern humans.