Scientists reveal a 1.5-million-year-old human face

A 1.5-million-year-old face is forcing scientists to rethink the origins and diversity of early humans.

An international research team led by Dr. Karen Baab, a paleoanthropologist at the College of Graduate Studies, Glendale Campus of Midwestern University in Arizona, created a digital reconstruction of the face of early Homo erectus. The fossil, known as DAN5, is dated to about 1.5 to 1.6 million years old and was discovered at Gona in Ethiopia's Afar region. The rebuilt face looks more archaic than many scientists expected, offering fresh clues about one of the first human species to expand across Africa and Eurasia. The results were published in Nature Communications.

Dr. Baab says the reconstruction adds a surprising new twist: "We already knew that the DAN5 fossil had a small brain, but this new reconstruction shows that the face is also more primitive than classic African Homo erectus of the same antiquity. One explanation is that the Gona population retained the anatomy of the population that originally migrated out of Africa approximately 300,000 years earlier."

Gona's Deep Record of Fossils and Stone Tools

The Gona Paleoanthropological Research Project in Ethiopia's Afar region is co-directed by Dr. Sileshi Semaw (Centro Nacional de Investigación sobre la Evolución Humana, Spain) and Dr. Michael Rogers (Southern Connecticut State University). The Gona area has produced hominin fossils older than 6.3 million years ago, along with stone tools covering the past 2.6 million years of human evolution.

For this reconstruction, scientists combined a fossil brain case (previously described in 2020) with smaller facial fragments from the same individual, DAN5, dated to between 1.6 and 1.5 million years ago. Using virtual methods, the team reassembled the face fragments (and teeth) to build what they describe as the most complete fossil human skull from the Horn of Africa for this time period. Researchers classify DAN5 as Homo erectus, a long-lasting species found across Africa, Asia, and Europe after about 1.8 million years ago.

How Micro-CT Scans Rebuilt the DAN5 Skull

To piece the fossil together, the team used high-resolution micro-CT scans of four major facial fragments recovered during fieldwork at Gona in 2000. They built 3D digital models from those scans, then carefully aligned and reassembled the fragments on a computer. Where possible, they positioned the teeth into the upper jaw. The final stage involved "attaching" the reconstructed face to the braincase to create a mostly complete cranium. The process took about a year and required multiple rounds of refinement before the team settled on the final reconstruction.

Dr. Baab, who led the reconstruction work, compared it to "a very complicated 3D puzzle, and one where you do not know the exact outcome in advance. Fortunately, we do know how faces fit together in general, so we were not starting from scratch."

A Mix of Homo erectus Traits and Older Features

The study suggests that the Gona population living around 1.5 million years ago combined traits typically associated with Homo erectus in the braincase with more ancestral features in the face and teeth that are usually linked to earlier species. The researchers point to examples such as a relatively flat bridge of the nose and large molars.

To reach these conclusions, the team compared the size and shape of the DAN5 face and teeth with fossils from the same geological age, as well as specimens that are older and younger. A similar trait combination has been reported before in Eurasia, but DAN5 is described as the first fossil showing this pattern within Africa. That finding challenges the idea that Homo erectus evolved outside Africa. "I'll never forget the shock I felt when Dr. Baab first showed me the reconstructed face and jaw," says Dr. Yousuke Kaifu of the University of Tokyo, a co-author of the study.

Dr. Baab argues the broader fossil record still points toward an African origin for the species: "The oldest fossils belonging to Homo erectus are from Africa, and the new fossil reconstruction shows that transitional fossils also existed there, so it makes sense that this species emerged on the African continent. But the DAN5 fossil postdates the initial exit from Africa, so other interpretations are possible."

Dr. Rogers agrees that the new skull highlights how varied early humans could be. "This newly reconstructed cranium further emphasizes the anatomical diversity seen in early members of our genus, which is only likely to increase with future discoveries."

Dr. Semaw adds that the fossil is also notable for its archaeological context: "It is remarkable that the DAN5 Homo erectus was making both simple Oldowan stone tools and early Acheulian handaxes, among the earliest evidence for the two stone tool traditions to be found directly associated with a hominin fossil."

What Comes Next for DAN5 and Early European Fossils

Next, the researchers want to compare DAN5 with some of the earliest known human fossils from Europe. These include remains assigned to Homo erectus as well as Homo antecessor, a distinct species, with both dated to around one million years ago. "Comparing DAN5 to these fossils will not only deepen our understanding of facial variability within Homo erectus but also shed light on how the species adapted and evolved," says study co-author Dr. Sarah Freidline of the University of Central Florida.

The team also hopes future discoveries will help test other possibilities, including scenarios involving genetic admixture between species, similar to what has been documented much later among Neanderthals, modern humans and "Denisovans." One idea is that DAN5 could reflect admixture between classic African Homo erectus and the earlier Homo habilis species. As Dr. Rogers puts it, "We're going to need several more fossils dated between one to two million years ago to sort this out."