A nearly complete 3.8-million-year-old skull found at Woranso-Mille in Ethiopia’s Afar region is the first cranium ever identified of Australopithecus anamensis, the presumed ancestor of Lucy’s species, scientists reported in August 2019.
The MRD cranium of Australopithecus anamensis, a 3.8-million-year-old fossil found at Woranso-Mille in Ethiopia’s Afar region and described in Nature in August 2019. (Dale Omori / Cleveland Museum of Natural History via Wikimedia Commons, CC0) [file photo]
The fossil, known as MRD, was described in two studies published in the journal Nature on Aug. 28, 2019, by a team led by the Ethiopian paleoanthropologist Yohannes Haile-Selassie of the Cleveland Museum of Natural History. Until then, A. anamensis, dated to between about 4.2 and 3.9 million years ago, had been known mainly from jaws, teeth and isolated bone fragments.
The upper jaw was found on Feb. 16, 2016, by Ali Bereino, a local worker from Afar, who brought it to Haile-Selassie’s attention. The team searched the area for 16 hours and recovered the rest of the skull, CNN reported. “I couldn’t believe my eyes when I spotted the rest of the cranium,” Haile-Selassie said. “It was a eureka moment and a dream come true.”
The site lies about 55 kilometres (34 miles) north of Hadar, where the partial skeleton of Lucy, a member of the later species Australopithecus afarensis, was found in 1974. The Woranso-Mille Paleoanthropological Research Project had been working in the area for 15 years.
A companion study led by Beverly Saylor of Case Western Reserve University dated the skull by studying the volcanic layers and sediments around it. The skull, which probably belonged to a male, appears to have been carried a short distance by a river and buried in the sand of a delta on the shore of a lake. The river was lined with trees, while the land farther away was dry, open shrubland.
The face has a mix of old and newer features. It juts forward, with forward-projecting cheekbones and large canine teeth, and its long, narrow braincase is small, like those of other early human ancestors. “MRD has a mix of primitive and derived facial and cranial features that I didn’t expect to see on a single individual,” Haile-Selassie said.
The find also changed the accepted picture of how the two species were related. Using MRD as a reference, the team identified a 3.9-million-year-old forehead fragment from the Middle Awash, known as the Belohdelie frontal, as belonging to A. afarensis. That means Lucy’s species and its presumed ancestor lived at the same time for at least 100,000 years, rather than one simply turning into the other.
“We used to think that A. anamensis gradually turned into A. afarensis over time,” said Stephanie Melillo of the Max Planck Institute for Evolutionary Anthropology, a co-author. “We still think that these two species had an ancestor-descendant relationship, but this new discovery suggests that the two species were actually living together in the Afar for quite some time.”
Haile-Selassie, speaking at a news conference in Addis Ababa, called the overlap a “game-changer in our understanding of human evolution during the Pliocene,” Al Jazeera reported. Fred Spoor of the Natural History Museum in London wrote in a Nature commentary that MRD “looks set to become another celebrated icon of human evolution.”
Sources: Haile-Selassie Y, Melillo SM, Vazzana A, Benazzi S, Ryan TM, “A 3.8-million-year-old hominin cranium from Woranso-Mille, Ethiopia,” Nature (Aug. 28, 2019), University of Michigan News (Aug. 28, 2019), CNN: “Skull of 3.8-million-year-old early human discovered in Ethiopia” (Aug. 28, 2019), Al Jazeera: “3.8-million-year-old skull in Ethiopia an evolution game-changer” (Aug. 29, 2019)