Published: Fri, August 30, 2019
Global News | By Blake Casey

Incredible Fossil Discovery Finally Puts A Face On An Elusive Early Hominin

Incredible Fossil Discovery Finally Puts A Face On An Elusive Early Hominin

The tiny skull was found nearly entirely intact in Ethiopia in 2016 and proves the two species co-existed for at least 100,000 years.

The fossil, dubbed MRD, which provides insight into a pivotal period for the evolutionary lineage that eventually led to modern humans, belongs to the species Australopithecus anamensis which first appeared 4.2m years ago.

The fossil was found in 2016 in what was once sand deposited in a river delta on the shore of a lake.

The first piece of the skull found was the upper jaw, which was exposed on the surface.

In this undated photo provided by the Cleveland Museum of Natural History in August 2019, Yohannes Haile-Selassie, holds a fossilised cranium of Australopithecus anamensis.

"MRD has a mix of primitive and derived [ancient] facial and cranial features that I didn't expect to see on a single individual", said Haile-Selassie in a press release.

Also working on this project were Stephanie Melillo, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany; Beverly Saylor, Case Western Reserve University; Luis Gibert, Universitat de Barcelona; Alan Deino, Berkeley Geochronology Center, Berkeley, California; Mulugeta Alene, Addis Abba University, Ethiopia; Stanley A. Mertzman, Franklin and Marshall College; Naomi Levin, University of Michigan; Mark Peaple and Sarah Feakins, University of Southern California; and Benjamin Bourel, Doris Barboni, Alice Novello and Florence Sylvestre, Aix-Marseille University, Aix-en-Provence, France. Analysis of the fossil's teeth and jaw allowed the researchers to assign the species as A. anamensis.

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A skull bone that had previously been attributed to A. anamensis now seems to better match A. afarensis, yet it has been dated to 3.9 million years ago.

Other clues as to the environment in which the specimen lived were provided by fossil pollen grains and the chemical remains of plants and algae, which are preserved in the lake and delta sediments. He and his colleagues also have argued, based on fossil evidence, for the existence of another australopithecine, Australopithecus deyiremeda, living between 3.5 million and 3.3 million years ago.

Researchers have discovered what they say is a remarkably complete cranium of an early human ancestor. Some characteristics were shared with later species, while others had more in common with those of even older and more primitive early human ancestor groups such as Ardipithecus and Sahelanthropus. "One of the most exciting aspects of this discovery is how it bridges the morphological space between these two groups", Melillo said. Lucy is widely credited with being the world's most famous early human ancestor.

"This is a game changer in our understanding of human evolution", Haile-Selassie said. The team say the skull "fills a major gap in the fossil record" and "shows that at least two related hominin species co-existed in eastern Africa around 3.8 [million years] ago, further lending support to mid-Pliocene hominin diversity". Due to the cranium's rare near-complete state, the researchers identified never-before-seen facial features in the species. "We're eager to conduct more work in these deposits to understand the environment of the MRD specimen, the relationship to climate change and how it affected human evolution, if at all", said Naomi Levin, a co-author on the study from the University of MI. In the second, researchers looked at how A. anamensis would have lived.

The current view that an ape named "Lucy" was among a species that gave rise to the first early humans may have to be reconsidered. That means the two species lived at the same time in the same region of East Africa, for at least 100,000 years. This species is the oldest of the Australopithecus genus.

For the past decade, the generally accepted idea, Strait said, was that Au. anamensis transformed over time into Au. afarensis, following in sequence like dancers in a conga line. After years of analyzing the cranium, Melillo said it is "good to finally be able to put a face to the name". The area was active and diverse, full of cliffs and the aftermath of volcanic eruptions. At the same time, A. anamensis also had some modern features, such as a reduction in canine size and a large cranium compared to A. afarensis - the species that supposedly came after A. anamensis.

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