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Australopithecus bahrelghazali

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Australopithecus bahrelghazali is an extinct species of australopithecine. These were early human relatives that lived during the Pliocene epoch. This species is significant because it was the first australopithecine discovered in Central Africa. Before this find, scientists believed these creatures lived only in East and Southern Africa. The discovery at Koro Toro, Chad, proved they were widely distributed across the continent.

Okavango Delta, Botswana
Okavango Delta, Botswana

The species is known from very few fossil remains. The most famous specimen is a jawbone nicknamed "Abel." This holotype specimen includes the premolars, canines, and a right second incisor. Researchers also found an isolated first upper premolar, known as a paratype. Other fragments include two additional partial jawbones from the K13 and KT40 sites. Because there are so few bones, some scientists argue it is actually Australopithecus afarensis. They believe the anatomical similarities between the two are too close to call them separate species.

Anatomy provides clues about how these creatures differed from their East African relatives. The jawbone of Abel has an almost vertical alveolar part, which is the section holding the tooth sockets. In contrast, the jaw of A. afarensis is more oblique. Abel also has two ridges on the tongue side of the jaw called a superior transverse torus and an inferior torus. These ridges are only moderately developed. Additionally, the chewing surfaces of the premolars have thin enamel. While some researchers noted three distinct tooth roots in the jaw, this trait might just be natural variation within the A. afarensis species.

Finding these fossils was the result of the Franco-Chadian Paleoanthropological Mission in 1995. A large team of experts reported the discovery. This group included Michel Brunet, Alain Beauvilain, Yves Coppens, Emile Heintz, Aladji Hamit Elimi Ali Moutaye, and David Pilbeam. They named the species after the Bahr el Gazel region. In classical Arabic, this name means "River of the Gazelles." In 1996, the team officially allocated the remains to this new species.

Determining the exact age of the fossils has been a complex task. In 2008, scientists used radiometric dating on a sedimentary rock called pelite. They measured the 10Be/9Be ratio to estimate the age. This test suggested the sediment was deposited 3.58 million years ago. However, some experts noted that Abel was not found in its original geological layer. This makes it difficult to know exactly which layer the fossil came from. Later tests in 2010 suggested an age of 3.65 million years. Michel Brunet agreed with an approximate age of 3.5 million years.

We can learn about the diet of A. bahrelghazali through carbon isotope analysis. This scientific method looks at the chemical signatures in teeth. The results showed high δ13C values. This indicates the species ate many C4 savanna foods. These include grasses, sedges, and underground storage organs like rhizomes. They also ate some C3 forest foods, such as fruits, flowers, pods, or insects. However, there is a mystery regarding their teeth. The teeth are not hypsodont, meaning they are not built for heavy grinding. The thin enamel also might not have survived the abrasive dirt found on underground roots.

The environment of Koro Toro was likely a lakeside grassland with sparse trees. It may have looked very similar to the modern Okavango Delta.

Okavango Delta, Botswana
Okavango Delta, Botswana

The area supported many large animals. Scientists found fossils of antelopes, elephants, white rhinoceroses, and giraffes. They also found pigs, horses, and Sivatherium. Aquatic life was also common, including catfish, hippos, otters, and turtles. These animals suggest the area had open-water lakes or streams. This ecosystem was likely connected to major waterways like the Nile and the Niger rivers.

This discovery changes how we view the movement of early hominins. It suggests that ancestors may have moved from East Africa through the Central African Shear Zone. The presence of similar animals in both East and West Africa implies that wildlife could migrate freely. Some scientists have even proposed a new genus called "Praeanthropus." This would group A. bahrelghazali with other early species like Sahelanthropus. While the classification of these species is still debated, A. bahrelghazali remains a vital piece of the puzzle.

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File:Okavango Delta, Botswana.jpg
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