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Panel a shows the Ledi-Geraru LD 760-115979 right canine compared with mirrored left canines from Hadar A. afarensis. Panels b\u2013d compare the LD 760 tooth with a right canine from A. afarensis and a mirrored left canine from A. garhi. The LD 760 canine has a simple, chisel-like wear pattern, unlike the multi-faceted wear of A. afarensis or the broad curved basin seen in A. garhi. Images are oriented to emphasize these differences and are not to scale. Fossil photos of the A. garhi holotype courtesy of the Middle Awash research project.<\/p>\n\n\n\n
At a sunbaked outcrop in Ethiopia\u2019s Afar Region, a handful of teeth are challenging the old story of a single, linear march from ape-like ancestors to us. Instead, they hint at a crowded evolutionary landscape where early Homo<\/a> and a newly recognized Australopithecus<\/a> species lived side by side between about 2.78 and 2.59 million years ago, well after Lucy\u2019s kind disappeared from the fossil record around 2.95 million years ago.<\/p>\n\n\n\n In a study published Aug. 13 in Nature<\/a>, an international team led by UNLV anthropologist Brian Villmoare describes 13 teeth that include early Homo and a distinct set from a previously unknown Australopithecus. The find underscores that human evolution resembled a branching tree more than a straight ladder.<\/p>\n\n\n\n The fossils come from layers bracketed by precisely dated volcanic ash. Among them are:<\/p>\n\n\n\n \u201cWe used to think of human evolution as fairly linear, with a steady march from an ape-like ancestor to modern Homo sapiens. Instead, humans have branched out multiple times into different niches,\u201d said lead author Brian Villmoare of the University of Nevada, Las Vegas<\/a>. He added, \u201cNature experimented with different ways to be a human as the climate became drier in East Africa, and earlier more ape-like species went extinct.\u201d<\/p>\n\n\n\n <\/p>\n<\/blockquote>\n\n\n\n For decades, sites spanning 2.95 to 2.0 million years ago have been rare, leaving a gap in the record as Australopithecus declined and Homo and Paranthropus<\/a> emerged. Ledi-Geraru offers a rare, well-dated sequence, with 40Ar\/39Ar<\/a> ages of 2.593 \u00b1 0.006 Ma for the Giddi Sands Tuff and 2.631 \u00b1 0.011 Ma for the Lee Adoyta Tuffs, firmly anchoring the fossils in time.<\/p>\n\n\n\n Tooth anatomy holds evolutionary clues. The Homo teeth show derived features like mesiodistal compression in the third premolar compared with pre-3.0 Ma australopiths. The Australopithecus individual has squarer lower molars, lacks the distinctive bilobate buccal contour of A. afarensis, and does not show the reduced hypocone or upper canine \u201ctalon\u201d basin seen in A. garhi. These traits point to a non-robust australopith unlike any previously known.<\/p>\n\n\n\n The overlap of early Homo and Australopithecus before 2.5 million years ago suggests a mosaic of parallel lineages, not simple ancestor-replacement. Between 3.0 and 2.5 million years ago, eastern Africa may have hosted as many as four hominin lineages: early Homo, A. garhi, the new Ledi-Geraru Australopithecus, and Paranthropus<\/a>.<\/p>\n\n\n\n Lucy\u2019s species, A. afarensis<\/a>, once seemed a tidy ancestor to later hominins. Its disappearance around 2.95 million years ago opened a dynamic interval now shown to be filled with early Homo and multiple australopiths. The Ledi-Geraru finds strengthen earlier hints of hominin diversity by 2.5 million years ago, in step with Paranthropus<\/a> records from Kenya and Tanzania.<\/p>\n\n\n\n The late Pliocene in East Africa was becoming drier and more open. Yet both Homo and Australopithecus occupied the same habitats at Ledi-Geraru, raising questions about diet, mobility, and resource use. Why Australopithecus persisted in Afar until at least 2.5 Ma, while Paranthropus appeared elsewhere, remains a puzzle explored in paleoecology<\/a> studies.<\/p>\n\n\n\n The new Australopithecus species remains unnamed, with only dental evidence so far. The authors urge caution, but the pattern is clear: evolution tried multiple hominin solutions in the late Pliocene. More fossils\u2014jaws, skulls, limb bones\u2014will help test whether diet, tool use, or subtle ecological differences explain the overlap.<\/p>\n\n\n\n \u201cThis is what we should be finding in the human fossil record. 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.\u201d<\/p>\n<\/blockquote>\n\n\n\n The teeth build on a 2.8-million-year-old Homo mandible from the same area, pushing our lineage closer to the end of A. afarensis. Elsewhere, sites in the Omo-Turkana Basin and northern Tanzania preserve early Homo and Paranthropus after about 2.0 Ma. Afar now stands out for keeping Australopithecus in the mix well after Lucy\u2019s time.<\/p>\n\n\n\n If early Homo was not uniquely tied to open, arid habitats, what factors truly drove its rise and persistence during this crowded evolutionary moment? Each new fossil from these layers could reshape our understanding of how climate, chance, and competition intertwined.<\/p>\n\n\n\nTwo Lineages, One Landscape<\/h2>\n\n\n\n
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A Fossil Gap Finally Fills<\/h2>\n\n\n\n
What The Teeth Reveal<\/h3>\n\n\n\n
Why It Matters Now<\/h2>\n\n\n\n
Key Findings At A Glance<\/h3>\n\n\n\n
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From Lucy To A Forest Of Branches<\/h2>\n\n\n\n
Climate, Niche, And Survival<\/h3>\n\n\n\n
What Comes Next<\/h2>\n\n\n\n
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Context In The Wider Record<\/h2>\n\n\n\n
A Closing Question<\/h2>\n\n\n\n
Study Details<\/h3>\n\n\n\n