(Republicaninformer.com)- Last month, Nature magazine published a study by a group of scientists that found that the oldest fossils of Homo sapiens in eastern Africa are much older than previously believed.
The fossilized remains, known as Omo I, were discovered in Ethiopia in the late 1960s. Since then, scientists have been attempting to precisely date them by using chemical fingerprints of volcanic ash layers both above and below the sediments in which the fossils were found.
Found in the Omo Kibish Formation in southwestern Ethiopia, the Omo I remains were discovered within the East Africa Rift valley which is an area of high volcanic activity as well as a rich source of early human remains and artifacts.
By dating the layers of volcanic ash above and below where the fossils were found, scientists concluded that Omo I is the earliest evidence of Homo sapiens.
But a team of scientists, led by the University of Cambridge, have reassessed the age of the Omo I remains. While earlier attempts to date the fossils suggested they were less than 200,000 years old, the new research found that Omo I have to be older than a volcanic eruption that took place 230,000 years ago.
Cambridge University’s Dr. Céline Vidal, the lead author of the study, it was generally accepted that the Omo fossils were less than 200,000 years, “but there’s been a lot of uncertainty around this date.”
According to Dr. Vidal, the Omo I fossils were found “in a sequence” underneath “a thick layer of volcanic ash” that had yet to be dated with radiometric techniques due to the ash’s fine grain.
As part of a four-year project led by Cambridge Professor Clive Oppenheimer, Dr. Vidal and her team have been trying to date off the major volcanic eruptions in the Ethiopian Rift that occurred during the late Middle Pleistocene period, when Homo sapiens emerged.
The team collected pumice rock samples from the volcanic deposits, grinding them down to sub-millimeter size. According to Dr. Vidal, once a rock is crushed, “you free the minerals within” which allows the scientists to date them.
The scientists conducted new geochemical analysis to link the fingerprint of the volcanic ash layer from the Kamoya Hominin Site with an eruption from the Shala volcano more than 400 kilometers away. They then dated pumice samples from the volcano to 230,000 years ago.
Since the Omo I fossils were found even deeper than this particular ash layer, the scientists concluded that the Homo sapien fossils must be older than 230,000 years.
