<text>  A momentous and valuable piece of our evolutionary history has gone on display to the public. The 2.8 million-year-old partially complete lower jaw, uncovered in the Afar region of Ethiopia, is thought to belong to a species that may have been the first member of the Homo family. It is significant because it suggests our first human ancestors emerged 400,000 years earlier than previously thought. The fossil is now encased in a glass box at the Arizona University. Scroll down for video . The 2.8 million-year-old partially complete lower jaw pictured, uncovered in the Afar region of Ethiopia, is thought to belong to a species that may have been the first member of the Homo family. The fossilised remains were put on display inside a glass case at Arizona University earlier this week . It was unveiled at a press conference by Professor Kaye Reed, one of the palaeontologists who made the discovery in January 2013. Scientists say the fossil, which is known as LD 350-1, is recognisably human but also has more primitive features that suggests it is older than other fossils belonging to the Homo family. This would make it the common ancestor for modern humans - Homo sapiens - and their extinct relatives including Homo habilis, Homo erectus and Neanderthals. Researchers who have digitally reconstructed the jaws of other ancient human ancestors say the fossil also matches what they would expect from this common ancestor. 55 million years ago - First primitive primates evolve . 15 million years ago - Hominidae great apes evolve from the ancestors of the gibbon . 8 million years ago - First gorillas evolve. Later, chimp and human lineages diverge . 5.5 million years ago - Ardipithecus, early proto-human shares traits with chimps and gorillas . 4 million years ago - Australopithecines appeared. They had brains no larger than a chimpanzees . 2.8 million years ago - LD 350-1 appeared and may be the first of the Homo family . 2.7 million years ago - Paranthropus, lived in woods and had massive jaws for chewing . 2.3 million years ago - Homo habalis first thought to have appeared in Africa . 1.8 million years ago - Homo ergaster begins to appear in fossil record . 1.6 million years ago - Hand axes become the first major technological innovation . 800,000 years ago - Early humans control fire and create hearths. Brain size increases rapidly . 400,000 years ago - Neanderthals first begin to appear and spread across Europe and Asia . 200,000 years ago - Homo sapiens - modern humans - appear in Africa . 40,0000 years ago - Modern humans reach Europe . The discovery, which was found in the Ledi-Geraru area of Afar, has put a new date on the emergence of the first man from our more ape-like ancestors. Dr Brian Villmoare, from the University of Nevada, Las Vegas, helped lead the fossil hunters, said: In spite of a lot of searching, fossils on the Homo lineage older than two million years ago are very rare. To have a glimpse of the very earliest phase of our lineages evolution is particularly exciting. LD 350-1 reveals that many of the anatomical patterns we see in 2 million-year old Homo were established much earlier in the evolution of the genus. At 2.8 million years ago we see relatively evolved Homo traits in combination with other much more primitive anatomical features. The researchers, whose work on the fossil is published in the journal Science, say the fossil could be a key missing link between the Homo lineage and a more primitive and ape-like rival branch of the hominin evolutionary tree called Australopithecus. Details of the Australopithecus are best known from a fossil named Lucy, dating back 3.2 million years, which was discovered in Ethiopia in 1974. But exactly how Homo habilis had appeared was unclear due to a huge gap in the fossil record. The new discovery has helped to fill that gap. Scientists say it can provide important clues to the changes in jaw and teeth that distinguished members of the Homo family from those belonging to Australopithecus. Until now the earliest evidence of the existence of the first Homo species was 2.3 million to 2.4 million year old fossils. Scientists have been searching for decades for earlier examples in an attempt to understand how our ancestors split from other ape-like hominins. Dr William Kimbel, director of the Institute of Human Origins at Arizona State University who was also involved in the research, said: The Ledi jaw helps narrow the evolutionary gap between Australopithecus and early Homo. Its an excellent case of a transitional fossil in a critical time period in human evolution. The bone was unveiled at a press conference by Professor Kaye Reed pictured, one of the palaeontologists who made the discovery in January 2013. Scientists say the fossil, known as LD 350-1, is recognisably human but also has more primitive features that suggests it is older than other fossils belonging to the Homo family . The fossilised lower jawbone, shown above with teeth still in the bone, was found in Ledi-Geraru in Ethiopia . The fossilised jawbone was first discovered by student Chalachew Seyoum from the Authority for Research and Conservation of Cultural Heritage in Ethiopia in January 2013. Until now, the earliest evidence of the existence of the first Homo species was 2.3 million to 2.4 million-year-old fossils. The jawbone is pictured . It is thought to be the left side of an adults lower jawbone that has canine, premolars and three molars still preserved in the jaw. Mr Seyoum said he was stunned when he saw the fossil. The moment I found it, I realised that it was important, as this is the time period represented by few fossils in Eastern Africa, he told BBC News last night. Dating of the fossil and the surrounding sediment suggest it is between 2.8 million and 2.75 million years old. Other fossils of antelope, prehistoric elephants and hippos discovered alongside the jawbone suggest that this early Homo species lived in open grassland and shrub habitats. This matches the picture that scientists believe was occurring around this time of climate change creating increasingly arid conditions in Africa. These are thought to be one of the main driving forces that led to the evolution of the Homo lineage and eventually our own species. Australopithecus, by contrast, was thought to inhabit far wetter environments and this may have contributed to their eventual demise. The researchers said that the changes in the new jawbone compared to Australopithecus suggest that evolution of different jaw shapes may have been a key step in the divergence of the two lineages. Professor Kaye Reed, also from Arizona State University, said: We can see the 2.8 million year aridity signal in the Ledi-Geraru faunal community, but its still too soon to say that this means climate change is responsible for the origin of Homo. The images above show the jawbone from different angles and how many of the teeth still remain in place . Anthropologists digging tin the Ledi-Geraru, pictured above, discovered the new jawbone in January 2013 . The new fossil has helped fill a huge gap in the evolutionary history above of how the Homo family appeared . Another study published in the journal Nature has also provided convincing evidence that LD 350-1 was a common human ancestor to the Homo family. The jawbone was found in the Ledi-Geraru area, marked with a star on the map above, of Ethiopia . They used 3D imaging techniques to scan partial skull of Homo habilis - a human ancestor that lived 1.8 million years ago and is thought to have been among the first to use tools - earning it the nickname handy man. It reveals an unexpectedly primitive structure, indicating that the species may have originated at least 2.3 million years ago and allowed the researchers to draw conclusions about what their ancestors jaw would have looked like. Their findings suggest that three different species of early human existed side-by-side between 2.1 million and 1.6 million years ago - Homo habilis, Homo erectus and Homo rudolfensis. Scientists used 3D imaging techniques to reconstruct the skull of Homo hablis left which has provided clues about how this now extinct member of our evolutionary branch would have looked. The image on the right shows an early reconstruction of Homo hablis at the Westfälisches Museum for Archaology in Herne . They found that the ancestor of Homo habilis would have had features similar to those found in the fossilised jawbone LD 350-1. Professor Fred Spoor, a researcher of evolutionary anatomy at University College London and the Max Planck Institute in Germany, said: By digitally exploring what Homo habilis really looked like we could infer the nature of its ancestor, but no such fossils were known. Now the Ledi-Geraru jaw has turned up as if on request, suggesting a plausible evolutionary link between Australopithecus afarensis and Homo habilis. This reconstruction of the jaw of Homo habilis by the UCL team shows that it was more primitive than the jaws of Homo erectus or Homo sapiens and was more similar to the jaw of Australopithecus afarensis . Dr Simon Underdown, an anthropologist at Oxford Brookes University, said the discovery of LD 350-1 could help scientists unravel the complex beginnings of our own species. He said: It gives us a better understanding of what was happening at the earlier end of the genus Homo. Finds like Kenyanthropus a 3.5 million year old ape-like species have made it harder to understand the relationship between the Australopithecines and us - in short its the replacement of the old fashioned unilinear model of a evolutionary branch with a multiple species based evolutionary bush. Whats becoming clear is that we have only a small part of the jigsaw puzzle. This new fossil may well be a member of our genus, an australopithecine or an hitherto unknown genus. 