The Afar Triangle: When Our Ancestors Shared the World with Apex Predators

In March 2026, palaeontologists described a new species of giant crocodile in the Journal of Systematic Palaeontology: Crocodylus lucivenator, a 4.6-metre reptile exhumed from the Hadar Formation in Ethiopia. This crocodile is not merely a scientific curiosity: it lived 3 to 4 million years ago, beside the same lakes and rivers as Australopithecus afarensis, our direct bipedal ancestors. This geographical and temporal coincidence offers an opportunity to explore one of the most intense environments in human evolutionary history: the Afar Triangle.

The Afar Triangle: Geology of a Cradle

The Afar Depression is one of the most geologically active zones on Earth. Located at the junction of the African, Arabian and Somali plates, it hosts the East African Rift — a gigantic tectonic trench that, millions of years from now, will separate the Horn of AfricaAfricaThe cradle of humankind: the continent where the first hominins appeared, then Homo sapiens around 300,000 years ago, before the expansion to the rest of the world.→ from the rest of the continent. This permanent geological instability — volcanoes, earthquakes, collapses — has permitted the deposition of exceptionally well-preserved stratigraphic layers, making the region an unrivalled fossil archive.

The Hadar Formation, located in north-eastern Ethiopia, is the richest archive of this period. Its sedimentary layers, deposited between 3.4 and 2.9 million years ago, have yielded an extraordinary harvest of fossils since 1972: australopithecineAustralopithecineA genus of bipedal hominins from Africa (c. 4.2–1.9 Ma) with a brain still close to that of great apes (400–550 cm³) but walking upright. Lucy (<em>Au. afarensis</em>) is the most famous specimen.→ bones, OldowanOldowanThe oldest known stone-tool industry (c. 3.3–1.7 Ma), characterised by flaked pebbles (choppers) and basic flakes. Named after Olduvai Gorge (Tanzania).→ tools, PliocenePlioceneA geological epoch spanning roughly 5.3 to 2.6 million years ago, the last subdivision of the Neogene. It was during the Pliocene, in an East Africa undergoing cooling and forest fragmentation, that the first fully bipedal australopithecines such as Lucy (~3.2 Ma) evolved.→ fauna remains. The first excavations, led by Maurice Taieb, Donald Johanson and Yves Coppens, culminated with the discovery of "Lucy" in 1974 — a 40% complete female skeleton that transformed our understanding of human origins.

The Afar Australopithecines

Australopithecus afarensis is the flagship species of this environment. Bipedal yet still strongly arboreal, with a small brain (400-550 cm³) and a prognathous face, it represents a clearly intermediate stage of evolution between our common ancestors with the great apes and the earliest representatives of the genus Homo. Its family tree is more complex than once thought: Australopithecus deyiremeda, discovered in 2015 a few kilometres from Hadar, shows that several australopithecine species coexisted in the same region at the same time.

Crocodylus lucivenator: the 2026 Discovery

It is in this context that Crocodylus lucivenator enters the scene. This giant crocodile, 4.6 metres long, is described from cranial fragments and vertebrae exhumed at Hadar. It is distinguished from current species by a more robust jaw and more massive teeth, adapted to seizing large prey. Its contemporaries — the australopithecines — stood approximately 1.1 to 1.5 metres tall and weighed 25 to 50 kg. An encounter between an A. afarensis and a Crocodylus lucivenator at a water's edge would have had only one possible outcome.

This discovery illustrates a reality often minimised in reconstructions of human prehistoryPrehistoryThe span of human history before the invention of writing, from the Palaeolithic to the Metal Ages, known mainly through material remains.→: our ancestors were not dominant predators but potential prey in a dangerous ecosystem. Bite marks identified on homininHomininMember of the subtribe Hominina, comprising the human lineage (Homo, Australopithecus, Paranthropus…) but excluding orangutans and gibbons. The term progressively replaces "hominid" in its narrow sense.→ bones at several African sites confirm that large predators — big cats, giant hyenas, crocodiles — exerted intense selective pressure on our lineages. It is partly to escape, or resist, this pressure that bipedalismBipedalismA mode of locomotion on two hind limbs, the defining trait of the human lineage, appearing over 7 million years ago. Visible in the anatomy of the pelvis, femur and foramen magnum.→, sociality and intelligence were favoured by natural selection. The Hadar Formation has not yet revealed all its secrets, and future campaigns will push the stratigraphyStratigraphyThe study of the superimposed layers (strata) of an archaeological site; each layer corresponds to a phase of occupation and yields a relative chronology.→ further back, toward the very first moments of bipedal evolution.