Gona is a paleoanthropological research area in Ethiopia's Afar Region. Gona is primarily known for its archaeological sites and discoveries of hominin fossils from the Late Miocene, Early Pliocene and Early Pleistocene. Fossils of Ardipithecus and Homo erectus were discovered there. Two of the most significant finds are an Ardipithecus ramidus postcranial skeleton and an essentially complete Homo erectus pelvis. Historically, Gona had the oldest documented Oldowan artifact assemblages. Archaeologists have since found older examples of the Oldowan at other sites. Still, Gona's Oldowan assemblages have been essential to the archaeological understanding of the Oldowan. Gona's Acheulean archaeological sites have helped us understand the beginnings of the Acheulean Industry.
History Paleoanthropological interest in the locality that would eventually become the Gona Paleoanthropological Research Project area began after a French geologist, Maurice Taieb, undertook a geological reconnaissance survey of the Afar Rift in the late 1960s. This initial research led to an archaeological survey of the area around the Kada Gona River. During the survey, the researchers found artifact-bearing deposits. The first excavation occurred in the West part of the Gona Project area in 1976; this site has since been named WG1. In the early 1980s, the Ethiopian government passed a moratorium on archaeological fieldwork. In 1987, the newly established People's Democratic Republic of Ethiopia allowed archaeological fieldwork to resume. This decision permitted Selshi Semaw to conduct his first survey of Gona's archaeological sites. Soon after this initial survey, Semaw initiated the Gona Paleoanthropological Research Project.
The first systemic excavations of Gona sites by Semaw and his colleagues took place between 1992 and 1994. Two sites they excavated during this period, East Gona 10 (EG-10) and East Gona 12 (EG-12), yielded a high density of artifacts attributed to the Oldowan stone tool industry. The artifacts from these sites were eventually dated to 2.6 Ma (million years ago) using radiometric dating and magnetostratigraphy.
Only a few years after the initial publication of the East Gona sites, Semaw and colleagues described two new sites in the Ounda Gona South area, Ounda Gona South 6 (OGS-6) and Ounda Gona South 7 (OGS-7) dated to 2.6 Ma. OGS-6 and OGS-7 are important sites for understanding the early Oldowan because the stone tool assemblages were associated with fossilized animal bones with cut marks on their surfaces. Up to this point in the early 2000s, very little archaeological evidence was available to corroborate many archaeologists' theory that hominins used early Oldowan stone tools for processing animal carcasses to obtain meat.
Gona was widely known for many years as the site with the oldest Oldowan artifacts. However, in 2019 the results from an excavation at the Bokol-Dora 1 site in the Ledi-Geraru Research Project area in the Ethiopian Lower Awash Valley were published. The excavation at Bokol-Dora 1 recovered Oldowan artifacts that are between 2.61 and 2.58 Ma. The archaeologists who published on this site suggest that the artifacts are closer to 2.58 Ma. However, there has been some controversy regarding this date. Then, in 2023, a report from an excavation at Nyayanga, Kenya, on the Homa Peninsula found Oldowan artifacts in sediment dated 3.032 to 2.581 Ma. With two assemblages with earlier dates for their Oldowan artifacts, archaeologists do not think the Gona Oldowan assemblages are the oldest documented instance of the Oldowan. Even though the Oldowan artifact assemblages from Gona are not the oldest, they are still significant because they help researchers understand hominin behavior.
Geography The Gona Paleoanthropological Research Project is a area of badlands within the west-central part of Ethiopia's Afar Region. The southernmost boundary of the project area is the Asbole River. The northernmost is the Bati-Mille Road. The Eastern border is the Hadar Research Project area. The Western Ethiopian Escarpment forms the westernmost extent of the project area. There are five major tributaries of the Awash River in the Gona Research Project area from northernmost to southernmost: the Kada Gona, the Ounda Gona, the Dana Aoule, the Busidima River, and the Asbole River. Most of Gona's sites are near these five rivers, so many of the sites in the project area are named based on the tributary they are closest to and the cardinal direction of the site related to the river. For example, sites south of the Ounda Gona are called Ounda Gona South (OGS), followed by the site number.
Paleoanthropology Hominin fossils from Gona are used by palaeoanthropologists studying human evolution in the Late Miocene, Early Pliocene and Early Pleistocene.
Ardipithecus Researchers collected several fossil teeth attributed to Ardipithecus kadabba in two different localities: the Escarpment and Asbole Dora. The fossils were dated using their stratigraphic location within the Adu-Asa Formation, which dates to the Miocene. The fossils from the Escarpment are approximately 5.4 million years old, and those from Asbole Dora are around 6.3 million. The age of these teeth situates them within the time frame of the speciation of the chimpanzee and human lineages. When researchers analyzed these teeth, they had features associated with the pattern in later hominin dentition. These observations help reconstruct a crucial time in hominin evolution for which very little evidence is available.
Ardipithecus ramidus fossils have been collected from Early Pliocene sediments at multiple localities in the Gona Western Margin area. These localities are associated with the As Duma fault. The fossils were dated using the established geochronology for the project area, argon-argon dating, and additional non-hominin fossils from the same period. The date range for these fossils is between 4.8 and 4.32 million years ago. Most of the fossils are fragments that are not associated with a single individual. These fossils consist of isolated teeth, parts of the maxilla, mandible, and postcranial bones from the hands, feet, and lower leg. The Gona Western Margin 67 locality is unique because researchers think the fossils found are from a single individual. They believe they are from a single individual because none of the bones have duplicates, and the elements' size and level of preservation are consistent. The majority of the elements of the skeleton collected are from the feet and legs. One of the main questions that paleoanthropologists want to understand is how bipedalism evolved. Ar. ramidus has adaptations for walking on two legs but retains a lot of adaptations for arboreality. The Gona Western Margin 67 individual has helped researchers understand how Ar. ramidus walked on two legs. Particularly how variation in anatomy impacted the way they walked.
Homo erectus Researchers also have found Homo erectus fossils in the Gona project area. At Busidima North 49 (BSN49), paleoanthropologists found an adult female's lumbar vertebra and an almost complete pelvis. This locality of the Gona project area is part of the Busidima geological formation. Geologists used sediment accumulation for the formation to narrow the range of dates. The fossil is likely from between 1.4 and 0.9 million years ago. This fossil is significant in the paleoanthropological community because there are very few pelvic H. erectus fossils, and this fossil pelvis is essentially complete. There is a specific research question in human evolution known as the obstetric dilemma, where the female pelvis had to develop novel adaptations to accommodate the large size of the neonatal head due to the expansion of the brain during human evolution. Before collecting and describing this fossil, researchers thought that H. erectus did not have modifications in the pelvis to account for the larger brain size of their babies. However, this conclusion was based on estimating the shape of the H. erectus birth canal from the Turkana Boy fossil because that was what was available then. Simpson and colleagues were able to describe specific modifications in the Gona pelvis related to changing the size and shape of the birth canal in modern humans, which proved that H. erectus did have adaptations in the anatomy of their pelvis for giving birth to larger-brained offspring.
Two other H. erectus fossils were parts of the skull found at different archaeological sites. The earlier site, Dana Aoule North 5 (DAN5), is dated between 1.6 and 1.5 Ma. Busidima North 12 (BSN12) is younger. It dates to 1.26 Ma. The DAN5 H. erectus cranium was small and gracile. In contrast, the BSN12 skull was more robust and larger. Initially, researchers suggested that the differences in the two skulls resulted from sexual dimorphism and that the smaller skull was a female. But findings from further investigations did not support this claim. These researchers thought that the size and shape differences of the two fossil skulls were related to the expansion of H. erectus brain size over time and not sexual dimorphism.
Geology
Geological setting The Gona Paleoanthropological Research Project is within the Afar Triangle, a geological depression created by the East African Rift system. The site is a classic rift basin formed via rifting and volcanism. The As Duma fault is a major geological feature in the project area, which forms the western half of the Awash half-graben. The Adu-asa formation shows the most volcanic activity and volcanic rocks dominate its sediments. The Sangatole and Hadar formations have a decreased level of volcanic activity and an increase in sedimentation rates. The Busidima formation shows a decrease in sedimentation, evidence of a drainage system, and a large river. Sedimentation ended after 0.16 Ma when the Awash River incised the area. The incision of the Awash River created badlands that characterize the project area today.
Geochronology +Gona's geochronologyGeological formationAge (Ma)Busidima Formation2.7 - < 0.15Hadar Formation3.9 - 2.9Sagantole Formation< 5.2 - 3.9Adu-asa Formation> 6.4 - 5.2 Gona's geological formations span the last 6.4 million years. The dates for the archaeological sites and fossils from Gona rely on the project area's established geochronology and detailed stratigraphy. Geologists used tephrostratigraphy, paleomagnetic dating, and argon-argon dating to construct Gona's geochronology.
Archaeology
Oldowan technological behavior The Oldowan assemblages from Gona play a significant role in research seeking to understand the technological behavior of Oldowan tool makers. Technological behavior describes actions related to producing and using a particular technology, such as Oldowan artifacts. Stone knapping follows the principles of conchoidal fracture mechanics. Flaking must be approached in a specific way to achieve the desired outcome of the tool maker. The desired result of Oldowan stone tools was to create a sharp cutting edge. The tool maker would have to make a series of technical choices to make a sharp cutting-edge during manufacturing. They needed to select an appropriate raw material with a structure amenable to conchoidal fracture. They would have chosen a particular knapping technique, which in most cases would be hard hammer percussion. They would employ a specific reduction strategy, which is the pattern of how they reduced the core to create flakes. Archaeologists are interested in these choices because looking at the variation in these choices allows researchers to form inferences about why this variation occurs. These inferences inform the goal of this type of archaeological research, which is to understand the relationship between tool use and hominin biological evolution.