According to a new research, Chororapithecus abyssinicus, a predecessor of both apes and humans, originated in Africa, not Eurasia, nearly 2 million years earlier than commonly thought. Up until now, researchers believed that the split between human and ape lines took place around five to six million years ago. The new study debunks this belief, thanks to concrete fossil evidence that push back the timeline of human evolution by at least two million years.
The Hominidae family is made up of gorillas, orangutans, chimpanzees, humans and three other currently-extant primate species. Our current knowledge of hominid evolution is based primarily on molecular and genetic science. In recent years, however, the discovery of million-year-old fossils in Ethiopia, like that of C.abyssinicus, has helped enhance our understanding of how and when humans split away from the great ape family. Speaking about the new research, Giday WoldeGabriel, a geologist at Los Alamos National Laboratory and the study’s leader, said:
Our new research supports early divergence: 10 million years ago for the human-gorilla split and 8 million years ago for our split from chimpanzees. That’s at least 2 million years earlier than previous estimates, which were based on genetic science that lacked fossil evidence.
With the help of advanced geological and research techniques, the scientists managed to determine the period during which the now-extinct gorilla-like creature, Chororapithecus abyssinicus, existed. Recently published in the Nature journal, the findings were the result of thorough examination of the volcanic ash present in Ethiopia’s Chorora region. According to the team, frequent volcanic eruptions and earthquakes in the area had previously entombed the fossils, which have only recently come to surface due to years of erosion and ground motion.
In the 1990s, the same team was responsible for uncovering the fossilized remains of as many as eight hitherto-unknown hominid species, including the 4.4 million-year-old Ardipithecus ramidus and its older relative, Ardipithecus kadabba. Both of these species were quite possibly the earliest ancestors of Homo sapiens, after they split from the main ape family tree. As the scientists point out, the individuals of the Ardipithecus genus were bipedal, unlike apes or chimps. They were, however, not as evolved as humans. WoldeGabriel added:
Our analysis of C. abyssinicus fossils reveals the ape to be only 8 million years old, younger than previously thought. This is the time period when human and African ape lines were thought to have split, but no fossils from this period had been found until now.
Among the fossils recovered from the dig site at Ethiopia were nine teeth fragments belonging to C. abyssinicus. The teeth, according to the researchers, were similar to that of gorilla, and were likely adapted for a fibrous diet. Recent analysis of the remains has revealed that the common ancestor of humans and chimpanzees existed much earlier than what genetic science previously indicated.
To calculate the age of the fossilized teeth, the scientists took the help of several techniques. For instance, using argon-dating and paleomagnetic methods, the team determined the age of the rocks and soil present around the fossils. Additionally, they studied the patterns of magnetic reversals, comparing it with their knowledge of the era’s magnetic orientation. Finally, the sediments were calibrated using the Geomagnetic Polarity Time Scale (GPTS).
The research is all the more significant as it provides evidence that our ancestors evolved in Africa and not Eurasia, where hominid fossils were more abundant. The study was the result of a collaboration between scientists from Japan, Ethiopia and the United States.
Source: Los Alamos National Laboratory