Eritrea: Fossil is missing link in elephant lineage
Fossil finds illuminate the history of Earth that was utterly dark for modern-day researchers. National Geographic’s April 2003 cover story titled ‘The rise of Mammals’ attests that studies on DNA have complemented and enhanced research capacity on fossils.
© PNAS / Illustration by Gary H. Marchant
Similar history has been made when a fossil found in Dogali along the eastern escarpment of Eritrea in 1997 gave scientists new ideas about the evolutionary trend of elephants. In 1998, Jeheskel Shoshani, currently professor of biology at the University of Asmara, moved to Eritrea to study a unique population of elephants who had been isolated from other members of the species, leading to inbreeding and genetic mutations. Researching the elephants proved extremely difficult, however, as the herd roamed an area on the Ethiopia-Eritrea border. Participating local and foreign researchers published a scholarly paper in the Proceeding of the National Academy of Science of the United States of America (PNAS) in October 2006.
In November 2006 a similar report was published by the University of Michigan: a pig-sized, tusked creature that roamed the Earth some 27 million years ago represents a missing link between the oldest known relatives of elephants and the more recent group from which modern elephants descended. The study was carried out by an international team that includes University of Michigan palaeontologist William J. Sanders.
This group's findings suggest that mastodons and the ancestors of elephants originated in Africa– in contrast to mammals such as rhinos, giraffes and antelopes – which had their origins in Europe and Asia and migrated into Africa. The dating of the new fossil, discovered in Eritrea, also pushes the origins of elephants and mastodons five million years farther into the past than previous records, Sanders said.
“The new fossil from Eritrea is important because it shows aspects of dental anatomy in common with the advanced group, including molars with more cusps and complex crowns and the delayed maturation and emergence of molars”. But the creature of the new fossil also had characteristics in common with palaeomastodonts, namely smaller body size and a jaw structure that suggests shorter tusks and trunk.
In the summer of 1997, Melake Ghebrekristos, a farmer in Dogali, found a jawbone in his farm and assessed that it was totally different from the bones with which he was familiar. According to fossil evidence this creature had a long snout and small tusks and it feed mostly on vegetation. Examination of the bones revealed that they were dated between 27 to 28 million years old. This is highly significant. Elephants date back some 55 million years, but modern elephants only assumed their present appearance and size about one million years ago. Until now, scientists had never discovered any elephant remains from between 34 million to 24 million years ago.
Professor Shoshani found it hard to place the bone with any other kind of animal known before and dedicated full-time study to the case.
Detailed study and analysis of the teeth on the jawbone are necessary to identify the species of the subject was conducted. It is believed that it belongs to the proboscideans – large mammals with trunks – of which modern day elephants are their descendants. It was found that the formation of the teeth occupied an intermediate structure between modern and ancient elephants. In addition, it exhibited horizontal tooth displacement that is still found in modern elephants. This feature is believed to be the oldest fossil evidence yet to be uncovered.
Furthermore, the paper lists how the researchers extrapolated the size of the animal: at about 130 cm tall at the shoulder and 484 kg body mass on average. These sizes clarify that it was much smaller than modern elephants, although it was young adult and not yet fully grown. The researchers also indicated that the animal was not a fully grown individual and it probably would have reached a larger size. The analysed data and the animal’s features allowed the researchers to put it between the classes of Elephantimorpha and Elephantida between which there existed a missing link gap – which is “a hypothesis that was predicted 84 years ago”. This is on the line of evolution of modern elephants. Professor Shoshani also went on to add, “[The discovered individual] is intermediate by size, by physical characteristics, and by date – all these things make it a missing link.” For that reason, the significance of the discovery of this animal is very important, as it sheds light on the evolution of elephants.
Members of the research group did not want to credit themselves by naming the finding in PNAS (Proceedings of the National Academy of Sciences of the United States of America), named the species as Eritreum melakeghekristosi, after Eritrea, the country where it was found, and Melake Ghebrekristos, who found the specimen and recognised it importance. He said he hoped this would help encourage the people of Eritrea to assist scientific research.
To Eritrea, this discovery, is an important one which complements the already excavated findings – and many more that are likely to be hidden somewhere awaiting further excavation and research. Since Eritrea is in the great African Rift Valley, which is known for its role as a laboratory in the evolution of mammals, it would not be a surprise to uncover more discoveries. However, considerable care should be taken in safeguarding artefacts and relics that carry invaluable history. Speaking on this, Dr Seife stresses that everyone should be aware of the importance of the country’s historical heritage, which is full of untold stories that cannot be retrieved once destroyed.
The findings in Dogoli, Abdur, and Buya have placed Eritrea as one of the major repositories of human evolution and culture. Protecting the unique natural heritage of Eritrea is an asset to be promoted through ecotourism for this and future generations. This report is the first combined account on the extinct and extant mammalian fauna of Eritrea. Prior to 1993 all publications concerning faunal assemblages from Eritrea were under the heading of Ethiopia, as Eritrea was then a province of Ethiopia. Data presented here, it is hoped, will serve as a basis for future research on the paleozoogeography and neozoogeography of Eritrean mammals.
