BETWEEN three million years ago (or Ma) and 2.5 Ma, there were as many as four hominin lineages living in eastern Africa.
They were the early Homo, Paranthropus, A. garhi, and the newly discovered Ledi-Geraru Australopithecus, according to a study which describes the age, geologic context and dental morphology of the new fossils.
The study, led by scientists at the Arizona State University, is published August 13 in the scientific journal Nature, looked at fossilized teeth that were unearthed by the Ledi-Geraru Research Project in northeastern Ethiopia, eastern Africa.
Over the past few decades, according to the study, the African hominin fossil record predating 3 Ma has expanded to include several potential ancestors.
Currently, systematic analyses place A. afarensis as the most likely candidate for the middle Pliocene from which multiple later hominin genera (that is, Homo and Paranthropus), and possibly other species of Australopithecus, descended.
A. afarensis was geographically and temporally widespread, and fossil sites with its remains are known from Tanzania to northern Ethiopia and, potentially, Chad. However, temporally, A. afarensis is not known after 2.95 Ma.
Paranthropus and Homo are well-documented in the eastern African fossil record after 2 Ma, especially in the Omo-Turkana Basin and at northern Tanzanian localities. But the hominin fossil record between the last appearance of A. afarensis (around 2.95 Ma) and 2 Ma is patchy.
The Ledi-Geraru Research Project is located towards the northern extent of the Afar Region. New discoveries in Ledi-Geraru suggest that early Homo and Australopithecus were both present in the Afar Region before 2.5 Ma, just as early Homo and Paranthropus are found in the Omo-Turkana Basin and sites to the south after about 2 Ma.
The Ledi-Geraru Research Project area contains fossil sediments from the critical 3-2 Ma time period. The study describes and evaluates hominin specimens discovered in 2015 and 2018 from the area. The species of Australopithecus is “new to science,” Scientific American reports.
The teeth unearthed in northeastern Ethiopia belong to what it describes as an “entirely new species of human ancestor… a previously unknown branch of humanity.”
“Once upon a time, scholars thought that human evolution was a march of progress in which our forebears evolved in linear fashion from an apelike ancestor to a series of increasingly humanlike forms,” writes Kate Wong, an award-winning science writer and senior editor at Scientific American.
The new find underscores the complexity of human origins, she says.
“Although Homo sapiens is the only hominin species on Earth today, for the vast majority of humanity’s existence, multiple hominin species shared the planet,” Wong continues. “Our family tree is more like a bush, with lots of twigs that were dead ends – failed evolutionary experiments that occurred outside of our direct line of ancestry.”
We dwell at length on this incredible story because it illustrates how simple teeth could upend conventional thoughts on our origins.
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Dr. Joseph D. Lim, Ed. D., is the former Associate Dean of the College of Dentistry, University of the East; former Dean, College of Dentistry, National University; Past President and Honorary Fellow of the Asian Oral Implant Academy; Honorary Fellow of the Japan College of Oral Implantologists; Honorary Life Member of the Thai Association of Dental Implantology; and Founding Chairman of the Philippine College of Oral Implantologists. For questions on dental health, e-mail jdlim2008@gmail.com or text 0917-8591515.
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Dr. Kenneth Lester Lim, BS-MMG, DDM, MSc-OI, graduated Doctor of Dental Medicine, University of the Philippines, College of Dentistry, Manila, 2011; Bachelor of Science in Marketing Management, De la Salle University, Manila, 2002; and Master of Science (MSc.) in Oral Implantology, Goethe University, Frankfurt, Germany, 2019. He is an Associate Professor; Fellow, International Congress of Oral Implantologists; and Fellow, Philippine College of Oral Implantologists. For questions on dental health, e-mail limdentalcenter@gmail.com
