The origins of the human race have fascinated our brightest minds for countless centuries. Through archaeological digs, experts have pieced together an understanding of our evolution from apes to Homo sapiens. And though there still remain unfilled gaps in our collective knowledge, a new discovery could hold the missing link to humanity’s ascent – and provide new light on how we all came to be.
The site of Woranso-Mille sits around 300 miles from the Ethiopian capital of Addis Ababa. On the surface, the area – which is near the borders of Djibouti and Eritrea – may seem pretty unremarkable. But for paleoanthropologists, this site is one of the most important places for deciphering the clues to our very existence.
Fossils found in the area have shed incredible light on the ascent of humans; after all, scientists unearthed the famous Lucy skeleton in 1974 only 18 miles away from the site. A member of the Australopithecus afarensis species – a descendant of humankind that lived between 3.9 and 2.9 million years ago – the discovery is one of paleoanthropology’s most treasured relics.
Certainly, Lucy was an important specimen – especially in aiding our understanding of how humans evolved to walk on two feet. But scientists have had less luck with the ancestor of Australopithecus afarensis, known as Australopithecus anamensis. The latter hominin, which was first discovered in 1965, roamed the Earth around 3.9 to 4.2 million years ago, though experts have only recovered teeth, jaw and arm fragments from the species.
However, everything changed in February 2016 when a startling discovery was made in Woranso-Mille, in Ethiopia’s Afar region. Strangely enough, the finding was made not by a scientist, but rather a goat herder named Ali Bereino who was digging in the area, which was around three miles from Miro Dora. Amazingly, Bereino had been building an extension onto a goat pen when he came across a piece of jaw bone known as a maxilla jutting out of the ground.
Bereino then contacted a government official in the area, who concurred that the find would be of interest to Yohannes Haile-Selassie, co-leader of a team digging at Woranso-Mille. The herder, for his part, had something of a reputation among the group of scientists. For a long time, Bereino had reported fossil discoveries in the area; but whenever Haile-Selassie had made the journey to this area, he had found nothing.
However, on this occasion Haile Selassie invited Bereino to bring the specimen in. Since first surveying the site in 2004, the former and his team had unearthed 120 individual fossils over the subsequent years. But this relic would be among the most important that his team has found thus far.
Excited by the fragment, Haile-Selassie walked over two miles to Bereino’s pen in search of the rest of the skull. Upon arrival, the former hunted the surrounding area in a frenzied attempt to find the specimen’s cranium. And eventually, he saw what looked like the missing piece of the puzzle protruding from the earth.
Haile-Selassie explained to National Geographic in August 2019 that he immediately lost his cool after finding the cranium piece. He said, “I didn’t even pick it up, and I started jumping up and down.” Moreover, his excited behavior spooked a government official along for the ride. Haile-Selassie recalled, “[He] looked at me and told his local friends, ‘What is going on with the doctor? Is he going crazy?’”
Above all, however, was the feeling that Haile-Selassie had stumbled upon something game-changing. He told CNN that same month, “I couldn’t believe my eyes when I spotted the rest of the cranium. It was a eureka moment and a dream come true. This is one of the most significant specimens we’ve found so far from the site.”
Haile-Selassie then went back to camp, with the skull and maxilla wrapped in a scarf and bandana. Paleontologist and study co-author Stephanie Melillo then recalled her colleague’s reaction upon returning, saying, “I’ve never seen him so happy in my life. He couldn’t even get the words out of his mouth; his hands were shaking.”
Before the team could do anything else, however, they decided to scour Miro Dora for any other relics. During a gruelling 16-hour dig, the researchers sifted through layers of soil – which included a fair amount of goat droppings – accumulated over time. However, this dirty work would lead the team to discover more fragments from the site.
After carefully recovering the skull from its resting place, the team then began the long process of analyzing the specimen. Overall, the analysis – which included extensive cataloguing of its dimensions and cross-referencing them with other fossil records – took three years. Experts then theorized that the bones likely belonged to the Australopithecus anamensis species.
Consequently, this meant that the specimen they had recovered was the first Australopithecus anamensis skull ever found. Melillo told CNN, “[It] was already a species that we knew quite a bit about, but this is the first cranium of the species ever discovered. It is good to finally be able to put a face to the name.”
Being the oldest skull of its kind, MRD – named after Miro Dora – taught the scientists a lot about this prehistoric species. In the team’s study published in Nature in August 2019, they observed how MRD possessed larger canine teeth than most early humans. However, its size compared to that of apes clearly identifies it as a hominid.
Furthermore, other aspects of MRD’s features helped the researchers determine more about the diet and behaviors of the Australopithecus anamensis species. It had a large protruding face with cheekbones sticking out; perfect for chomping on food that was difficult to chew.
In addition, researchers were able to build a reconstruction of MRD’s head using its skull as a template. In doing so, they revealed that the specimen boasted a surprising combination of both human and ape features. Halie Selassie told CNN, “MRD has a mix of primitive and derived facial and cranial features that I didn’t expect to see on a single individual.”
According to CNN, a team of paleoanthropologists, geologists and paleobotanists from around the world then scoured the surrounding area where the MRD skull was found. And thanks to this effort, they were able to gleam a number of fascinating insights regarding the species’ habitat.
Based on soil found in the area, these experts concluded that MRD’s remains were buried by flowing water. This in all probability means that the pre-human – much like today’s mammals – lived by a river or another body of water. As the paper’s co-author Naomi Levin from the University of Michigan speculated to CNN, the creature “lived near a large lake in a region that was dry.”
With the analysis of MRD’s features complete, Haile-Selassie and his team then moved on to determining the specimen’s age. To do this, they turned to geologist Beverly Saylor, who led a team to conduct an investigation of the discovery site’s soil. And by collecting samples of earth around where the skull lay, she helped piece together MRD’s time frame.
In the samples, Saylor and her team discovered particles of radioactive potassium-40. Due to the element’s consistent half-life, the geologist could accurately carbon date the relic to a precise moment in the Earth’s pre-history. Somewhat surprisingly, however, this information contradicted some of the pre-established theories regarding the Australopithecus anamensis.
To shed some context on this finding, one must first consider the era that the Australopithecus anamensis was originally believed to have lived in. The earliest known fossils of the species were dated between 4.2 and 3.9 million years ago; MRD, on the other hand, is believed to be from around 3.8 million years ago.
Of course, MRD’s discovery completes missing details about the time frame of the Australopithecus anamensis. As stated in the Woranso-Mille team’s report published in Nature, the specimen “fills a major gap in the fossil record” and extends the period that the species is believed to have existed. Moreover, it brings this species closer in period to when the Australopithecus afarensis roamed the planet.
In a discussion with CNN, Melillo explained the significance behind the find. She said, “Until now, we had a big gap between the earliest-known human ancestors, which are about six million years old, and species like ‘Lucy,’ which are two to three million years old. One of the most exciting aspects of this discovery is how it bridges the morphological space between these two groups.”
But perhaps the most important part of the study came when researchers cross-checked the skull with other specimens. In particular, the team referred to a 3.9 million-year-old piece of skull called the Belohdelie frontal. Discovered in 1981 in the same part of Ethiopia, the sample had so far eluded categorization – until MRD made them see the fossil in a whole new light.
Through comparison with MRD’s features, scientists realized that the Belohdelie frontal belonged to an already documented species. It came from the Australopithecus afarensis – the same species as Lucy. And this led to a startling revelation about our ancestors and human evolution.
Prior to the discovery of MRD, paleoanthropologists widely believed that pre-humans evolved through a process called anagenesis. Simply put, this theory purports that our early ancestors shared a single line of descent and gradually evolved into more complex organisms through time. In other words, it means that one species died off to give way to another.
However, the emergence of MRD and the identification of Belohdelie offers an alternate viewpoint. If the Australopithecus afarensis lived as long as 3.9 million years ago then this means that the Australopithecus anamensis species – like the 3.8 million-year-old MRD – lived at around the same time. As a result, the truth about human evolution may be much more complicated than first thought.
“Traditionally, we’ve thought of our evolution in a linear manner,” Haile-Selassie commented on the discovery to CNN. “But they must have overlapped for at least 100,000 years.” Naturally, this has led the scientist to consider new approaches to understanding our ancestors. Haile-Selassie continued, “How did a new species appear when [the] parent species was there?”
“We used to think that Australopithecus anamensis gradually turned into Australopithecus afarensis over time,” Melillo told CNN. “We still think that these two species had an ancestor-descendent relationship, but this new discovery suggests that the two species were actually living together in the afar for quite some time.”
Melillo then suggested how the two species might have lived side-by-side, saying, “[The discovery] changes our understanding of the evolutionary process and brings up new questions – were these animals competing for food or space?”
To answer the question of whether one species could emerge while the parent species was still there, the team looked at the areas that these creatures once occupied. Due to the distance between their habitats, they speculated that they could have lived in isolated communities – and subsequently evolved over time.
The habitats shared by the Australopithecus afarensis and Australopithecus anamensis would have been subject to massive amounts of physical change. Volcanoes in the region would have given the ground a wildly new topology, while seismic and continental shifts would have also split their homes even further apart.
Certainly, this idea could explain why one species eventually outlasted the other. During the Australopithecus afarensis’ time on Earth, the continent of Africa was becoming less populated by woodlands and dominated by open spaces. In turn, this pushed the species to begin walking upright on two feet and adapt to a new and complex diet.
By all means, the theory of isolated communities is convincing. However, experts such as Melillo still believe there are more lines of inquiry that need to be followed. For example, did the two species mix in some form?
Of course, there is definitely a case to be made for the two species coming into conflict at some point. It has long been theorized that in later years Homo sapiens were responsible for the extinction of Neandarthals – our closest descendants – due to fighting and the spread of pandemics. Could some of our earliest ancestors have also succeeded through a similarly violent streak?
In any case, however, what matters to the team are the valuable insights they’ve gleaned from MRD. Through its discovery, Haile-Selassie and the other experts have found a new chapter to add to humanity’s long and evolving story. Despite this, though, there are still some who remain skeptical to this new hypothesis.
Some scientists, like paleoanthropologist William Kimbel from Arizona State University’s Institute of Human Origins, believe that a consensus can only be made once more fossils are discovered. He told National Geographic, “In order to have confidence… one needs really good sample sizes, both within time planes and across times. You cannot make a strong claim on the mode of evolution based on only two specimens.”
Naturally, this is something the expedition is working on. And the group have many more studies ahead of them to confirm their theory. Of particular note, they already plan to use MRD’s taxonomy to categorize previously unidentified specimens. If their work is successful, they could push back the time frame of the Australopithecus afarensis even further.
Whatever their result, the Woranso-Mille team have already made a discovery beyond their wildest imaginations. Melillo explained to National Geographic, “It really fills you with wonder. To be able to see the face of this entity I was already so familiar with and have so many ideas about was super cool.”