It is generally accepted by palaeoanthropologists that the genus Homo evolved from an Australopithecus species somewhere in East Africa, most likely in the Afar region of Ethiopia, where the famous Australopithecus afarensis specimen “Lucy” was found. However, it is now widely recognised that the hominin evolutionary tree was far from straightforward, resembling more a tangled bush with side-branches that went extinct, rather than a simple, linear progression.
Given the tendency of our ancestors to diversify and occasionally interbreed, it is entirely possible that the genus Homo emerged from a hybrid population, or even that early Homo back-bred with ancestral australopithecines — especially when two or more species lived in close proximity, as new evidence suggests they did in the Afar region.
Maps showing (left) the location of the Ledi-Geraru site within the Horn of Africa on the left, and the location of the Australopithecus and Homo teeth on the right
Images by Penn State Associate Research Professor Erin DiMaggio.
Of course, because evolution operates over entire populations and across thousands of years, the distinction between the immediately ancestral Australopithecus and the descendant Homo is inherently arbitrary. It likely means far more to modern palaeoanthropologists than it ever did to the hominins themselves.
This new evidence, discovered by an international team working on The Ledi-Geraru Research Project, led by scientists at Arizona State University, indicates that both the unidentified Australopithecus and early Homo lived in the area between 2.6 and 2.8 million years ago. The age estimates were reliably established using volcanic ash layers immediately above and below the fossil-bearing strata. The team’s findings were published recently, open access, in Nature.
How Teeth Help Reconstruct Ancient Lives.The work is also summarised in an Arizona State University news release.
Teeth are among the most durable parts of the skeleton, often surviving long after other bones have decayed or been destroyed. For palaeoanthropologists, they are a treasure trove of information:
- Species Identification – The size, shape, and arrangement of teeth can reveal evolutionary relationships and help distinguish between species. Differences in cusp patterns, enamel thickness, and jaw proportions can be diagnostic.
- Diet and Lifestyle – Microscopic wear patterns on teeth (dental microwear) indicate what an individual was eating in their final days or weeks, while chemical analysis of tooth enamel can reveal long-term dietary patterns and even the types of plants consumed.
- Development and Growth – Teeth form in a predictable sequence during childhood. Studying the timing of tooth eruption and growth lines in enamel can give insights into life history traits, such as how quickly a species matured.
- Migration and Environment – The chemical composition of tooth enamel, particularly isotopes of oxygen and strontium, can preserve a record of the climate and geology of the region where an individual grew up, shedding light on migration patterns.
While teeth can suggest the presence of a previously unknown species, naming that species requires corroborating skeletal evidence to confirm unique anatomical traits and avoid misclassification.
ASU scientists uncover new fossils — and a new species of ancient human ancestor
The fossils found in northeastern Ethiopia date between 2.6M to 2.8M years ago, shed new light on human evolution
A team of international scientists has discovered new fossils at a field site in Africa that indicate Australopithecus and the oldest specimens of Homo coexisted at the same place in Africa at the same time — between 2.6 million and 2.8 million years ago. The paleoanthropologists discovered a new species of Australopithecus that has never been found anywhere.
The Ledi-Geraru Research Project is led by scientists at Arizona State University, and the site has previously revealed the oldest member of the genus Homo and the earliest Oldowan stone tools on the planet.
The research team concluded that the Ledi-Geraru Australopithecus teeth are a new species, rather than belonging to Australopithecus afarensis (the famous “Lucy”), confirming that there is still no evidence of Lucy’s kind younger than 2.95 million years ago.
This new research shows that the image many of us have in our minds of an ape to a Neanderthal to a modern human is not correct — evolution doesn’t work like that. Here we have two hominin species that are together. And human evolution is not linear — it's a bushy tree; there are life forms that go extinct.
Professor Kaye E. Reed, corresponding author
Institute of Human Origins and School of Human Evolution and Social Change
Arizona State University
Tempe, AZ, USA.
Reed is a research scientist at the Institute of Human Origins and President’s Professor Emeritus at the School of Human Evolution and Social Change at ASU. She has been co-director of the Ledi-Geraru Research Project since 2002.
Ledi-Geraru
What fossils did they find to help them tell this story? Teeth; 13 of them to be exact.
This field site has been famous before. In 2013, a team led by Reed discovered the jaw of the earliest Homo specimen ever found at 2.8 million years old. This new paper details new teeth found at the site that belong to both the genus Homo and a new species of the genus Australopithecus.
The new finds of Homo teeth from 2.6- to 2.8-million-year-old sediments — reported in this paper — confirms the antiquity of our lineage. We know what the teeth and mandible of the earliest Homo look like, but that’s it. This emphasizes the critical importance of finding additional fossils to understand the differences between Australopithecus and Homo, and potentially how they were able to overlap in the fossil record at the same location.
Brian Villmoare, lead author.
Department of Anthropology
University of Nevada Las Vegas
Las Vegas, NV, USA.
The team cannot name the species yet based on the teeth alone; more fossils are needed before that can happen.
How old are the fossils?
How do scientists know these fossil teeth are millions of years old?
Volcanoes.
The Afar region is still an active rifting environment. There were a lot of volcanoes and tectonic activity, and when these volcanoes erupted ash, the ash contained crystals called feldspars that allow the scientists to date them, explained Christopher Campisano, a geologist at ASU.
We can date the eruptions that were happening on the landscape when they're deposited. And we know that these fossils are interbed between those eruptions, so we can date units above and below the fossils. We are dating the volcanic ash of the eruptions that were happening while they were on the landscape.
Associate Professor Christopher J. Campisano, co-author
Institute of Human Origins and School of Human Evolution and Social Change
Arizona State University
Tempe, AZ, USA.
Finding fossils and dating the landscape not only helps scientists understand the species — it helps them re-create the environment millions of years ago. The modern faulted badlands of Ledi-Geraru, where the fossils were found, are a stark contrast to the landscape these hominins traversed 2.6 million to 2.8 million years ago. Back then, rivers migrated across a vegetated landscape into shallow lakes that expanded and contracted over time.
Ramon Arrowsmith, a geologist at ASU, has been working with the Ledi-Geraru Research Project since 2002. He explained the area has an interpretable geologic record with good age control for the geologic time range of 2.3 million to 2.95 million years ago.It is a critical time period for human evolution, as this new paper shows. The geology gives us the age and characteristics of the sedimentary deposits containing the fossils. It is essential for age control.
Professor J. Ramón Arrowsmith, co-author.
School of Earth and Space Exploration and Institute of Human Origins
Arizona State University
Tempe, AZ, USA.
What’s next?
Reed said the team is examining tooth enamel now to find out what they can about what these species were eating. There are still remaining questions the team will continue to work on.
Were the early Homo and this unidentified species of Australopithecus eating the same things? Were they fighting for or sharing resources? Did they pass each other daily? Who were the ancestors of these species?
No one knows — yet.
Whenever you have an exciting discovery, if you're a paleontologist, you always know that you need more information. You need more fossils. That's why it's an important field to train people in and for people to go out and find their own sites and find places that we haven't found fossils yet. More fossils will help us tell the story of what happened to our ancestors a long time ago — but because we're the survivors, we know that it happened to us.
Professor Kaye E. Reed.
ASU alumni and current faculty authors include: University of Nevada, Las Vegas Associate Professor Brian Villmoare; University of Arkansas Associate Professor Lucas Delezene; Virginia Commonwealth University Professor Amy Rector; Penn State Associate Research Professor Erin DiMaggio; ASU Research Professor David Feary; ASU PhD candidate Daniel Chupik; Louisiana State University Instructor Dominique Garello; Idaho College of Osteopathic Medicine Assistant Professor Ellis M. Locke; Boston University Senior Lecturer Joshua Robinson; West Virginia School of Osteopathic Medicine Assistant Professor Irene Smail; and the late ASU Professor William Kimbel.
Reed and Campisano talk more about this project in an in-depth interview.
Publication:
AbstractFinds like this are yet another reminder that the reality of our origins is far more complex, fascinating, and ancient than any creationist narrative allows. The coexistence of two different Australopithecus species alongside early Homo nearly three million years ago sits completely outside the narrow Biblical timeframe of a world created just a few thousand years ago. Such evidence is not merely inconvenient for creationism — it directly contradicts it.
The time interval between about three and two million years ago is a critical period in human evolution—this is when the genera Homo and Paranthropus first appear in the fossil record and a possible ancestor of these genera, Australopithecus afarensis, disappears. In eastern Africa, attempts to test hypotheses about the adaptive contexts that led to these events are limited by a paucity of fossiliferous exposures that capture this interval. Here we describe the age, geologic context and dental morphology of new hominin fossils recovered from the Ledi-Geraru Research Project area, Ethiopia, which includes sediments from this critically underrepresented period. We report the presence of Homo at 2.78 and 2.59 million years ago and Australopithecus at 2.63 million years ago. Although the Australopithecus specimens cannot yet be identified to species level, their morphology differs from A. afarensis and Australopithecus garhi. 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. Accordingly, there were as many as four hominin lineages living in eastern Africa between 3.0 and 2.5 million years ago: early Homo1, Paranthropus2, A. garhi3, and the newly discovered Ledi-Geraru Australopithecus.
Main
Over the past few decades, the African hominin fossil record predating 3.0 million years ago (Ma) has expanded to include several potential ancestors for later taxa4,5,6,7. Currently, systematic analyses place A. afarensis as the most likely candidate for the middle Pliocene stem taxon from which multiple later hominin genera (that is, Homo and Paranthropus), and possibly other species of Australopithecus, descended8,9,10. A. afarensis was geographically and temporally widespread, and fossil sites with its remains are known from Tanzania to northern Ethiopia and, potentially, Chad. However, temporally, A. afarensis is not known after 2.95 Ma (ref. 11).
Paranthropus and Homo are well-documented in the eastern African fossil record after 2.0 Ma, especially in the Omo-Turkana Basin and at northern Tanzanian localities12,13,14,15, but the hominin fossil record between the last appearance of A. afarensis (around 2.95 Ma) and 2.0 Ma is patchy. For example, no Paranthropus fossils have been recorded from the Afar Region to date, despite its presence in the Omo-Turkana Basin and at Nyayanga, Kenya2 at approximately 2.7 Ma and in the Upper Ndolanya Beds at Laetoli16 at about 2.66 Ma. Additionally, a Homo specimen at Ledi-Geraru, Ethiopia, extends the genus closer in time17 (2.78 Ma) to the last known appearance of A. afarensis1,11. However a simple cladogenic model of A. afarensis, or any other stem taxon, splitting into these daughter genera is complicated by the presence of A. garhi in the Afar3 at approximately 2.5 Ma.
The Ledi-Geraru Research Project (LGRP) area is located towards the northern extent of palaeoanthropological sites in the Afar Region, Ethiopia (Extended Data Fig. 1). New discoveries in Ledi-Geraru suggest that early Homo and Australopithecus were both present in the Afar Region before 2.5 Ma, just as early Homo and Paranthropus are sympatric in the Omo-Turkana Basin and sites to the south18,19 after about 2 Ma. Whether the apparent absence of Paranthropus from the Afar Region reflects the spotty nature of the fossil record or a biogeographical signal is yet to be determined. What is clear is that the Afar Region has currently yielded the only definitive evidence for Australopithecus in eastern Africa after 2.95 Ma—A. garhi and the newly discovered specimens from Ledi-Geraru.
Ledi-Geraru geologic context
The LGRP area contains fossiliferous sediments from the critical 3.0–2.0 Ma time period17. The fossil sites in the Lee Adoyta and Asboli regions of the LGRP area are located west of the Awash River in a region incised by the Mille and Geraru River drainages and their tributaries (Extended Data Fig. 1). The 3.0–2.5 Ma fossiliferous sediments are exposed in fault blocks bounded by post-depositional northeast–southwest and northwest–southeast trending faults (Fig. 1); age control is provided by many dated and correlated tephra deposits and by magnetostratigraphy17. Detailed 40Ar/39Ar dating methods are described in Methods.Fig. 1: Geologic context of the Lee Adoyta and Asboli regions.
a, Geologic map of the Lee Adoyta basin. Interbedded tuffs are shown as thin coloured lines. The black line indicates the position of the A–A′ cross-section shown in d. b, Stratigraphic sections at hominin localities showing the stratigraphic level of hominin fossil discoveries (yellow bones), fossiliferous horizons (white bones) and marker beds (coloured tuffs). Fossil and stratigraphic section locations are shown in a,c,d. c, Geologic map of the Asboli region superimposed on a hillshade image. Outcrops of multiple tephra deposits are shown as red lines, and these include the Giddi Sands and Lee Adoyta Tuffs that also occur in the Lee Adoyta region. d, South–north geologic cross-section of the Lee Adoyta basin showing the locations of hominin fossil sites. Vertical scale is doubled relative to the horizontal (2×VE).
The distribution and stratigraphy of fossiliferous units and tephra deposits provide context for the hominin fossils described here, which were discovered in sediments cropping out in the Lee Adoyta and Asboli regions (Fig. 1 and Extended Data Fig. 1). The Gurumaha sedimentary package is present in narrow fault-bounded exposures in the central Lee Adoyta basin and in drag-faulted blocks adjacent to basalt ridges bounding the basin to the east (Fig. 1a). The Gurumaha Tuff (GT), a light grey lapilli tuff dated to 2.782 ± 0.006 Ma (1σ; recalculated17,20), provides age control for the unit (Fig. 1b). Stratigraphically younger, the Lee Adoyta sedimentary package is widely exposed in the Lee Adoyta basin and is correlated to exposures in Asboli (Fig. 1). The Lee Adoyta Tuffs (LAT) comprise two thin, geochemically distinct tephras: a yellow altered basaltic ash which occurs approximately 10 cm above a white rhyolitic ash dated to 2.631 ± 0.011 Ma (1σ; recalculated17,20). These tuffs, and an underlying olive-green clay, provide an excellent marker sequence (Fig. 1b and Extended Data Fig. 2a). The Giddi Sands sedimentary package (Tgs; containing the Giddi Sands Tuff (GST)) and the Markaytoli sedimentary package (Tmk; containing the Markaytoli Tuff) crop out in the eastern Lee Adoyta basin (Fig. 1a). The base of the Giddi Sands sedimentary package is an erosional unconformity cutting into the Lee Adoyta sedimentary package in the Lee Adoyta Basin (Fig. 1b). The GST is a 3- to 8-cm-thick laminated, multicoloured (orange, yellow and white), crystal bentonite tuff. 40Ar/39Ar single-crystal incremental heating (SCIH) yielded a weighted-mean age of 2.593 ± 0.006 Ma (1σ) for the GST sampled in Asboli (Methods and Supplementary Figs. 1–3). In Asboli, the Giddi Sands sedimentary package containing the AS 100 fossil site unconformably overlies a sequence of mudstones containing the Asboli Tuffs, which in turn overlies the LAT exposed approximately 500 m to the south (Fig. 1c).
Villmoare, B., Delezene, L.K., Rector, A.L. et al.
New discoveries of Australopithecus and Homo from Ledi-Geraru, Ethiopia. Nature (2025). https://doi.org/10.1038/s41586-025-09390-4
Copyright: © 2025 The authors.
Published by Springer Nature Ltd. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)
If the Biblical account were true, there would be no record of long-extinct hominins separated from us by millions of years, nor any evidence of gradual change and branching lineages. Yet the rocks of the Afar region tell a different story — one of populations evolving, diversifying, and sometimes interbreeding over vast spans of time. This is the pattern we see consistently in the fossil record, and it is exactly what we would expect from evolutionary theory, not from literalist interpretations of ancient texts.
The teeth unearthed at Ledi-Geraru may be small, but they carry a message that is enormous in scope: our family history is deep, messy, and ancient, stretching back far beyond the limits of human memory or scripture. They speak of a world in which species came and went long before Homo sapiens appeared — a world best understood through science, not through the myths of a Bronze Age worldview.
In the language of the rocks, three million years is a whisper — but it’s still loud enough to drown out Genesis.
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