Fossil fragments of a face as well as teeth were reassembled to produce the most complete cranium of a human ancestor from this time in the Horn of Africa. (Credit: Karen L. Baab. Scans provided by National Museum of Ethiopia. Photographs courtesy of M. Rogers and G. Suwa.)

1.6-Million-Year-Old Fossil Combines Homo habilis Face With Homo erectus Brow Table of contents In A Nutshell

What did researchers find? A 1.6-to-1.5-million-year-old skull from Ethiopia combines features from two different stages of human evolution. The braincase and brow ridge match Homo erectus, but the face, teeth, and brain size look more like the earlier Homo habilis.

Why does it matter? The fossil shows that Homo erectus did not emerge as a neat package of traits. Different populations in East Africa appear to have been evolving at different speeds, with some retaining primitive features while others developed more modern characteristics.

What about the tools? Both simple stone tools and more advanced Acheulean hand axes were found at the same site. This raises questions about the assumed link between bigger brains and more sophisticated technology.

What’s next? With only six largely complete skulls from this period recovered in Africa, each new find reshapes the story. DAN5/P1 adds to growing evidence that human evolution was messier and more variable than textbooks suggest.

The skull had the brow of a descendant but the face of an ancestor. When researchers finished reconstructing the DAN5/P1 cranium from Ethiopia’s Afar region, dated to between 1.6 and 1.5 million years ago, they found themselves staring at an evolutionary contradiction: a single individual who appeared to belong to two different chapters of human history at once.

Homo erectus, the species that first looked recognizably like us with its large brain, prominent brow ridge, and smaller teeth, has long been considered a turning point in human evolution. The species is often described as a package of changes arriving together, but this newly reconstructed skull from the Gona research area indicates the pieces did not always move in lockstep.

The brain inside DAN5/P1 was small, just 598 cubic centimeters, closer to the earlier Homo habilis than to the larger-brained Homo erectus fossils found in Kenya from the same time period. Yet its jutting brow ridge and certain features of the braincase matched Homo erectus. Its face, meanwhile, retained the flat cheekbones and narrow nasal opening of species that should have been fading from the scene.

An international team led by Karen L. Baab of Midwestern University published their findings in Nature Communications. After years of digital reconstruction using micro-CT scans, they pieced together a mostly complete Early Pleistocene Homo cranium from the Horn of Africa, only the sixth such specimen recovered from the continent. What emerged was a fossil that defies easy classification and complicates our understanding of how Homo erectus came to be.

“The presence of such a morphological mosaic contemporaneous with or postdating the emergence of the indisputable H. erectus craniodental complex around 1.6 Ma implies an intricate evolutionary transition from early Homo to H. erectus,” the researchers wrote.

Map showing potential migration routes of the human ancestor, Homo erectus, in Africa, Europe and Asia during the early Pleistocene. Key fossils of Homo erectus and the earlier Homo habilis species are shown, including the new face reconstruction of the DAN5 fossil from Gona, Ethiopia dated to 1.5 million years ago. (Credit: Dr. Karen L. Baab. Scans provided by National Museum of Ethiopia, National Museums of Kenya and Georgian National Museum.) How Researchers Reconstructed the Homo Erectus Skull

The DAN5/P1 fossil was discovered at the Dana Aoule North site in Gona, part of Ethiopia’s Afar region. Initially, only the braincase had been fully studied. The face remained a puzzle, broken into fragments during fossilization and cemented together by sediment over millennia.

To reconstruct it, the team took micro-CT scans of five facial bone fragments: portions of both sides of the upper jaw, a piece of the region below the eye sockets, part of the cheekbone, and several teeth including premolars and molars. From these scans, they generated 3D surface models that could be digitally manipulated and fitted together.

Reassembly required matching each piece according to anatomical landmarks. Sutures had to align. Break lines had to correspond. The frontal process of the upper jaw, for instance, had to be angled so it would properly meet the frontal bone while simultaneously matching curvatures implied by surrounding structures. After the face was assembled, the team attached it to the previously reconstructed braincase.

To account for uncertainty in how the face connected to the braincase, the researchers also created an alternative reconstruction with slightly different positioning. Both versions produced similar results in subsequent statistical analyses, lending confidence that the findings were not artifacts of reconstruction choices.

A Face from the Past on a Skull from the Future

Comparing DAN5/P1 to other early human fossils revealed its split identity. The braincase aligned with Homo erectus in several respects: a thick, projecting brow ridge with a continuous groove behind it, circular eye sockets, and the long, low profile characteristic of the species.

But the face pointed backward in time. The area below the eye sockets was flat from side to side rather than curving outward as in typical African Homo erectus. The nasal opening lacked the pronounced widening seen in roughly contemporaneous Kenyan fossils like KNM-ER 3733 and the adolescent KNM-WT 15000. The cheekbone’s attachment point sat more toward the front of the face than expected, a trait linked to earlier Homo species.

Photo montage of five major elements of DAN5 fossil cranium.Photo montage of five major elements of DAN5 fossil cranium. (Credit: Dr. Michael Rogers)

The roof of the mouth was large relative to brain size, placing DAN5/P1 closer to early Homo and to Homo erectus fossils from Dmanisi, Georgia, than to East African Homo erectus. The teeth were also substantial. The first and third molars fell within the size range of Homo habilis and at the upper end of variation for African Homo erectus.

Statistical analyses of skull shape placed DAN5/P1 within the Homo erectus range but nearest to two specific fossils: the adolescent KNM-WT 15000 from Kenya and the subadult D2700 from Georgia. When the researchers analyzed midface shape alone, DAN5/P1 clustered with Homo habilis specimens instead. Its single closest match in overall shape was KNM-ER 1813, a classic Homo habilis skull from Kenya.

“DAN5/P1 is, to our knowledge, the first African fossil to exhibit a mixture of H. erectus and early Homo features,” the team reported.

Two Populations, Two Evolutionary Speeds

The combination of ancestral and more advanced features in a single skull from this time period complicates the conventional timeline. By 1.6 million years ago, Homo erectus was supposed to have already arrived as a coherent package. Famous Kenyan fossils from roughly the same period, including KNM-ER 3733 and KNM-WT 15000, display the full suite of Homo erectus traits: larger brains, smaller teeth, wider nasal openings, and curved architecture below the eyes.

Yet DAN5/P1 lived at essentially the same time with a brain barely larger than Homo habilis, teeth to match, and a face that looked like it belonged to an earlier era. The brow ridge announced membership in Homo erectus. Almost everything else pointed to something more primitive.

The researchers interpret this as evidence that different populations of early humans were evolving at different rates across East Africa. The rift basin landscape, combined with low population densities, may have allowed groups in the Horn of Africa and the Lake Turkana region of Kenya to diverge over time. The Horn of Africa population, represented by DAN5/P1, retained more ancestral features. The Kenyan population developed more derived characteristics.

“The evolutionary contrasts in brain size and face morphology embodied by the broadly contemporaneous DAN5/P1 and Kenyan fossils, KNM-ER 3733 and KNM-WT 15000, imply complex population structure rather than simple coexistence of two different lineages,” the researchers wrote.

This interpretation casts Homo erectus as a species showing substantial regional variation rather than uniform characteristics everywhere it lived.

Fossil fragments of a face as well as teeth were reassembled to produce the most complete cranium of a human ancestor from this time in the Horn of Africa. (Credit: Karen L. Baab. Scans provided by National Museum of Ethiopia. Photographs courtesy of M. Rogers and G. Suwa.) Advanced Tools Found at the Same Site as Small-Brained Fossil

Both simple and advanced stone tools turned up at the DAN5 site. Mode 1 tools, basic cores and flakes, appeared alongside Mode 2 Acheulean tools, the more sophisticated hand axes associated with Homo erectus.

Acheulean technology is typically linked to larger-brained populations. The longstanding assumption has been that expanding brains drove technological innovation. But at Gona, these advanced tools appear in the same context as a fossil with a brain volume comparable to Homo habilis, the earlier species credited only with simpler tools.

Evidence from the site also points to a broadened diet and access to animal resources. A similar pattern appears at Dmanisi in the Republic of Georgia, where small-brained fossils occur alongside evidence of meat consumption and varied tool use.

“The Gona evidence, along with that from Dmanisi, hints that key behavioral/technological innovations may precede major morphological transformations,” the team noted.

If accurate, the assumed connection between brain size and cognitive ability in early human evolution may have been less direct than researchers believed.

Homo erectus skull (oblique view) unrelated to study. Discovered in 1969 in Sangiran, Java, Indonesia. Dated to 1 million years ago. (© stockdevil – stock.adobe.com) Surprising Similarities to a Much Younger Species

DAN5/P1 also shares certain features with Homo naledi, a much younger Middle Pleistocene species discovered in South African caves. Both possess small brains, flat nasal regions, forward-positioned cheekbones, and a distinct bump at the back of the skull.

The researchers caution against reading too much into these resemblances. Vast stretches of time and thousands of kilometers separate the two fossils, and shared primitive traits do not necessarily indicate a direct evolutionary link. But the parallels add to mounting evidence that small-brained Homo populations persisted in Africa long after larger-brained forms had emerged.

One Skull, Many Questions

Only six largely complete Early Pleistocene Homo skulls have been recovered from Africa. Each new discovery reshapes the narrative, and DAN5/P1 is no exception. Here was an individual whose brow announced membership in Homo erectus while whose face and teeth belonged to an earlier inheritance, found at a site that also yielded both simple and advanced stone tools.

The fossil confirms that the emergence of Homo erectus involved considerable variation across populations. Different groups existed simultaneously in East Africa, evolving at different rates and retaining different features. The transition from early Homo to Homo erectus appears to have been gradual and uneven, with different traits shifting at different speeds in different places.

DAN5/P1 does not settle the debate over where Homo erectus originated or how it spread across Africa and into Eurasia. Some researchers have proposed a Eurasian origin based on early Homo erectus-like features appearing in Georgia. The ancestral morphology preserved in DAN5/P1, however, remains compatible with local evolution of the species in East Africa.

What the skull makes clear is that human evolution resisted the neat categories scientists have tried to impose on it. The individual with an ancestor’s face and a descendant’s brow is a reminder that our origins were anything but straightforward.

Paper Notes Limitations

Several sources of uncertainty affected the reconstruction. The most significant involved attaching the face to the braincase. The team addressed this by creating an alternative reconstruction with a more posteriorly positioned face; both versions produced similar analytical results. Smaller uncertainties relate to the positioning of the left and right portions of the upper jaw and the placement of the second and third molars, which had fewer anatomical constraints than other teeth. Dating precision also introduces ambiguity. The assigned range of 1.6 to 1.5 million years cannot entirely rule out a chronology where DAN5/P1 is geologically older than the Kenyan fossils to which it is compared, though this would not fundamentally change the evolutionary interpretation. Body mass estimates based on skull variables carry high error rates, and the researchers acknowledge this limitation when suggesting DAN5/P1 was smaller-bodied than its Kenyan contemporaries.

Funding and Disclosures

The Gona Project received continuous major support from the L.S.B. Leakey Foundation. Additional funding came from EU Marie Curie grants, Spain’s Ministry of Science and Innovation through project grants including PALEOAFRICA, GONAH, and ACHEULOAFRICA, the Wenner-Gren Foundation, the National Science Foundation, and the National Geographic Society. Infrastructure support was provided by the John and Lois Rogers Trust. The research permit was issued by the Ethiopian Heritage Authority, and the fossils are curated at the National Museum of Ethiopia. The authors declared no competing interests.

Publication Details

Authors: Karen L. Baab (Department of Anatomy, Midwestern University), Yousuke Kaifu (The University Museum, The University of Tokyo), Sarah E. Freidline (Department of Anthropology, University of Central Florida), Michael J. Rogers (Department of Anthropology, Southern Connecticut State University), Sileshi Semaw (Centro Nacional de Investigación sobre la Evolución Humana, Spain)

Journal: Nature Communications (December 16, 2025) | Title: “New reconstruction of DAN5 cranium (Gona, Ethiopia) supports complex emergence of Homo erectus” | DOI: 10.1038/s41467-025-66381-9 | Corresponding Author: Karen L. Baab ([email protected])

Glossary: The Gona Discovery

To help you navigate the specialized language of paleoanthropology, here are clear, conversational definitions for the terms used in the report on the DAN5/P1 skull discovery:

Acheulean (Mode 2): A more complex style of stone tool-making that includes hand axes. At DAN5, Mode 2 tools show up alongside other evidence that suggests behavior and anatomy didn’t always “upgrade” at the same pace.

Alveolar Clivus: The sloping area of the upper jaw below the nose and above the tooth roots. Researchers describe its forward tilt as “prognathic” when it angles outward.

Cranial Vault: The upper part of the skull that acts like a protective “box” for the brain.

Derived Trait: A physical feature that evolved more recently and differs from the “primitive” form found in ancestors. The paper identifies certain traits, like a projecting brow ridge, as being “derived” for Homo erectus.

Endocranial Volume (EV): The measurement of the space inside the skull, which tells researchers the approximate size of the brain. DAN5/P1 had a volume of 598 cubic centimeters, which is small compared with many African Homo erectus fossils from roughly the same time.

Frankfort Horizontal: A standardized way of orienting a skull so that the bottom of the eye socket and the top of the ear canal are on the same level. This allows scientists to compare different skulls accurately.

Maxillary Sulcus: A noticeable groove on the upper jaw (maxilla), near where the cheek region connects. In DAN5/P1, a well-developed maxillary sulcus is a feature more commonly seen in Homo erectus than in earlier Homo.

Mode 1: Simple stone tools such as cores and flakes. The DAN5 site includes both Mode 1 and Mode 2 tools.

Morphological Mosaic: An evolutionary “puzzle” where a single individual shows a mix of both very old (primitive) and newer (derived) physical characteristics.

Plesiomorphic (Primitive): Older, more ancestral traits that haven’t changed much from earlier forms. In DAN5/P1, examples include the flatter area under the eyes and a less projecting nasal region compared with Kenyan H. erectus fossils.

Supraorbital Torus: The formal name for the brow ridge—the bony shelf located above the eye sockets. The paper describes the DAN5/P1 ridge as vertically thick and projecting.

Taphonomic Distortion: Damage or changes that happen to a fossil after death, such as being crushed or warped by the weight of sediment over millions of years.