In the arid, fossil-rich sediment layers of Ethiopia’s northeastern Afar Region, a new window into human evolution has been revealed, challenging long-held assumptions about who walked the Earth between three and two million years ago.
Researchers with the Ledi-Geraru Research Project have uncovered a trove of fossilized hominin teeth that provide new insight into early members of our genus, Homo, and point to a previously unidentified species of Australopithecus that lived alongside early humans nearly 2.6 million years ago.
The finds, described in a new study published in Nature, suggest a far more diverse and dynamic hominin landscape in Eastern Africa than previously documented.
The discovery also helps fill in one of the most mysterious and underrepresented periods in the human fossil record: the gap between the last known appearance of Australopithecus afarensis (best known from the famous “Lucy” skeleton) around 2.95 million years ago and the widespread emergence of Homo and Paranthropus species after 2 million years ago.
“These specimens suggest that Australopithecus and early Homo co-existed as two non-robust lineages in the Afar Region before 2.5 million years ago, and that the hominin fossil record is more diverse than previously known,” the researchers write.
Until now, the prevailing narrative held that Australopithecus afarensis gave way to Homo and Paranthropus species in a relatively clean evolutionary split sometime around 2.8 to 2.5 million years ago. However, the new evidence from the Ledi-Geraru site, situated in a region of the Afar Desert west of the Awash River, suggests a more complicated picture.
Fossilized teeth from three separate sediment layers, dated to 2.78 Ma (million years ago), 2.63 Ma, and 2.59 Ma using high-precision argon dating, reveal a surprising overlap in hominin species.
A premolar attributed to Homo was recovered from the oldest sediment layer. In contrast, multiple teeth from a single individual, likely a new species of Australopithecus, were recovered from a layer just above. A separate pair of molars, also assigned to Homo, was found in the youngest strata.
In total, these fossils confirm the presence of Homo in the Afar Region as early as 2.78 million years ago, approximately 170,000 years after the last documented A. afarensis, and suggest an extended coexistence between Homo and at least one other Australopithecus lineage.
While the Homo specimens exhibit recognizable features, such as tooth shape, wear patterns, and crown proportions, the real surprise came from the Australopithecus teeth found in the Lee Adoyta sedimentary package. These molars and canines don’t match any known species, differing from A. afarensis and A. garhi in key ways.
For instance, the molars from the individual dubbed LD 760 are notably broad, lack the bilobate contours typical of A. afarensis, and exhibit wear and cusp patterns not seen in A. garhi. Likewise, the canines suggest a unique wear pattern and proportion more consistent with a distinct lineage.
The study’s authors considered several hypotheses, including that the LD 760 individual might represent a late-surviving A. afarensis. Additionally, the teeth could have come from an ancestral form of Paranthropus or a variant of A. garhi. Ultimately, researchers concluded that the teeth could only have come from a previously unknown species of early hominin.
“The Lee Adoyta teeth are a previously unknown species of Australopithecus from the early Pleistocene,” researchers write. “This hypothesis is the only alternative that offers no contradictions with the data presented in the previous three hypotheses.”
This discovery not only adds a new player to the hominin evolutionary tree but also reveals that the Afar Region, already famed for Lucy and other pivotal finds, was a hotspot of evolutionary experimentation.
The presence of both Australopithecus and Homo at Ledi-Geraru before 2.5 million years ago suggests that early Homo did not immediately outcompete or replace its relatives. Instead, these hominin species likely shared the same semi-arid landscape, possibly even occupying similar ecological niches.
That coexistence is a critical clue in understanding how early humans evolved not in isolation, but amid a complex web of evolutionary cousins.
“The diversity of hominins in the interval around 2.5 Ma demonstrates the ways in which evolution was experimenting with the overall hominin pattern,” the researchers write.
“This is what we should be finding in the human fossil record,” lead author and UNLV anthropologist at the University of Nevada, Las Vegas, Dr. Brian Villmoare, added in a press release. “Nature experimented with different ways to be a human as the climate became drier in East Africa, and earlier, more ape-like species went extinct.”
One conspicuous absence from the Afar Region during this time is Paranthropus, a genus known for its robust jaws and megadont teeth, which appears in Kenya and Tanzania around 2.7–2.6 million years ago. Despite its proximity to the south and west, no Paranthropus fossils have been found at Ledi-Geraru.
This raises another intriguing question of whether the presence of a late-surviving Australopithecus species could have blocked Paranthropus from colonizing this region.
“The apparent absence of Australopithecus after approximately 2.0 Ma in eastern Africa means that only two hominin genera remained, Homo and Paranthropus, and these were well differentiated in terms of their dietary ecology,” the authors noted, raising the question of whether niche competition played a role in shaping hominin geography and survival.
The new discoveries at Ledi-Geraru shift the evolutionary timeline and add to the list of known hominin lineages. Together with other recent findings, such as evidence of primitive human relatives and early hominin activity in Europe nearly 2 million years ago, they underscore the incompleteness of humanity’s origin story.
Nevertheless, with at least three separate hominin lineages now confirmed in the Afar Region between 3.0 and 2.5 million years ago —Homo, A. garhi, and this newly identified Australopithecus —the picture of our humanity’s past becomes more complex, and, perhaps most importantly, more accurate.
“We used to think of human evolution as fairly linear, with a steady march from an ape-like ancestor to modern Homo sapiens,” Dr. Brian Villmoare explained. “Instead, humans have branched out multiple times into different niches.”
Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan. Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com