The Persian Plateau, the "hub" where Homo sapiens lived for 20,000 years before conquering Eurasia

There is a gap in the story of our species. Homo sapiensHomo sapiensThe present-day human species, which emerged in Africa around 300,000 years ago, the only surviving human lineage after the extinction of Neanderthals and Denisovans.→ left 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.→ in a major dispersal some 70,000 to 60,000 years ago, yet Eurasia was not settled in a stable, widespread way until around 45,000 years ago. Between those two milestones lies an interval of roughly twenty thousand years about which almost nothing was known. Where did the ancestors of all non Africans live during that long parenthesis? A study published in March 2024 in Nature Communications offers a reasoned answer, by combining palaeogenetics and palaeoecological modelling. The signal points to one specific region, the Persian Plateau, which is argued to have served as a turntable, a "hub", for our species before it spread across three continents.¹

The work is authored by Leonardo Vallini, Carlo Zampieri, Mohamad Javad Shoaee and colleagues, under the direction of Luca Pagani of the University of Padova, with the participation of Michael Petraglia of Griffith University in Australia.¹ Its subject is neither an excavation nor a fossil, but a reconstruction: to recover, through computation, the place where a population stood during the initial phase of the peopling of Eurasia. The stakes go beyond geography. The point is to understand how, from a small founding group, the diversity of every people now living outside Africa came to unfold.

A missing link of twenty thousand years

The broad outline of the out of AfricaOut of AfricaThe dispersals of Homo sapiens out of Africa, including a major expansion c. 70,000 to 60,000 years ago and earlier exits.→ scenario is now well established. A population of Homo sapiens crossed the African threshold, probably by way of southern Arabia or the Levantine corridor, some 60,000 to 70,000 years ago. All non Africans today descend from that branch. But the archaeological traces of a massive and lasting settlement in Europe, East Asia and Oceania multiply only from around 45,000 years ago. Between the departure and that expansion, the record is almost silent. Sites are scarce, scattered, often hard to interpret.

It is this void that the team set out to fill. The guiding idea is simple to state: if humans did not immediately spread everywhere, it is because they first gathered somewhere. A region must have served as a demographic reservoir, a home base from which successive waves of settlement later departed. The authors call this region the "hub", the turntable. The concept did not appear in 2024: an earlier publication by the same team, in 2022, had already proposed the existence of such a focal area on the basis of genetics and material culture.⁵ The 2024 study goes further by locating that hub in space.

The reasoning rests on one central fact: during that period, the lineages that would give rise to Europeans, East Asians and Oceanians were still close to one another, not yet fully differentiated. They shared a recent common ancestor outside Africa. To find that ancestor is to find the hub.

One point is often misunderstood and deserves emphasis. The exit from Africa that peopled the world was not our species' first foray beyond the continent. Homo sapiens remains found in the LevantLevantA region of the eastern Mediterranean Near East (Israel, Lebanon, Syria, Jordan), a major crossroads of the first human migrations out of Africa.→, at Skhul and QafzehQafzehA cave in Lower Galilee (Israel) yielding Homo sapiens and some of the oldest known burials outside Africa.→, attest to far earlier presences, around one hundred thousand years ago. But those pioneers left almost no genetic trace in present day populations. They died out or were diluted. The decisive dispersal, the one we all descend from, is later, and it is its unfolding that the hub finally helps to articulate. Between the crossing of the threshold and the final dispersal, the common ancestors did not evaporate: they waited somewhere, and that somewhere has a history.

The genetic signal, a focal area east of the Zagros

To locate this ancestral population, the researchers had to disentangle nearly forty thousand years of admixture, migration and replacement that have blurred the genetic map of South West Asia. This is the technical core of the study. By reconstructing the relationships between ancient and present day populations, they looked for which living group best preserves the signature of that hub population.¹

The answer, unexpected in its precision, points to the populations of the Persian Plateau, that is, the zone extending east of the Zagros range, corresponding to present day Iran, Afghanistan and Pakistan. They are the ones that show the strongest affinity with the ancestral component common to all non Africans. In other words, the genetic background of this region's inhabitants carries, better than anywhere else, the memory of the founding population. PalaeogeneticsPalaeogeneticsThe study of ancient DNAAncient DNAGenetic material preserved in old remains, often degraded, sequenced with cutting-edge techniques.→ extracted from remains (bones, teeth, sediments, walls) to reconstruct the past of populations.→ reveals here an ancient and lasting differentiation, a sign that this focal area hosted a stable population over a long span before fanning out.

This result takes into account a crucial episode of our prehistoryPrehistoryThe span of human history before the invention of writing, from the Palaeolithic to the Metal Ages, known mainly through material remains.→, the bottleneckBottleneckA sharp, temporary reduction in a population's size that lastingly impoverishes its genetic diversity.→ that followed the exit from Africa. The founding group of non Africans was numerically small, which reduced the genetic diversity carried off the continent. The hub is not Africa regained: it is the stage where that small group paused, endured, then became structured before the great dispersal. The authors stress, however, the status of their conclusion. It rests on inference from models and available data, not on ancient genomes directly sampled in the region, which remain very rare. It is a strong hypothesis, one that field archaeology will have to test.

A discreet player complicates and enriches the picture: the "Basal Eurasians". This name designates a ghost lineageGhost lineageAn ancient human population known only by the trace it left in the genomes of present-day populations, without any confirming fossil.→, detected indirectly in the genome of certain ancient populations, which is thought to have split very early from the rest of the non Africans and to have received little, or perhaps no, Neanderthal DNADNAThe molecule carrying genetic information, used to reconstruct kinship between species.→. The team's models seek to situate where this deep branch may have stood relative to the hub. Disentangling these branchings, estimating the timing of each split, correcting for the later admixtures that artificially drew distinct groups together: this is the patient statistical work that leads to the designation of the Persian Plateau. The conclusion is not a geographic hunch, it is the point of convergence of a web of genetic constraints.

A refuge the climateClimateThe long-term average atmospheric conditions of a region; its variations (glaciations, aridifications) shaped migrations, agriculture and the collapse of prehistoric societies.→ made habitable

Genetics says where to look; palaeoecologyPalaeoecologyThe study of past ecosystems and their relations with the environment, reconstructed from fossils, DNA and sediments.→ checks whether the place could play the part. The researchers therefore modelled the climate and resources of South West Asia over the period concerned, in order to estimate each region's capacity to feed a human population. The Iranian Plateau stands out as an environment able to support a larger population than the other regions of western Asia at the same time.¹

The plateau's strength lies in its diversity. Highlands and inland basins, rivers running down from the relief, a mosaic of altitudes and habitats: this variety offered complementary resources and fallback zones during unfavourable climatic episodes. Where the neighbouring deserts and steppes imposed severe constraints, the plateau retained habitable pockets. It formed a refuge, in the sense that biologists give the term: a region where a population can persist when conditions harden all around.

Archaeology already provides anchor points. In the southern Zagros, Pebdeh Cave has yielded traces of occupation by hunter gatherers dating back to about 42,000 years ago.³ These markers remain modest against the scale of the phenomenon being reconstructed, and that is precisely what the study underlines: the region has been insufficiently explored. The model designates a target for excavations to come. It must also be recalled that the Zagros and its surroundings are not an isolated case: several refugia of western and central Asia may have played a supporting role, without however matching the carrying capacity that the models attribute to the plateau.

This notion of a refuge deserves to be taken seriously, for it changes how one pictures the period. We readily imagine the first Homo sapiens outside Africa as tireless walkers, pressing on without respite toward new horizons. The hub proposes the opposite image: that of a population long settled on the scale of millennia, well established in a generous territory, that sets off again only in fits and starts, when demography or climate pushes it to. The Persian Plateau was not a stage on a road, but a destination in itself, inhabited for a span comparable to the one that separates us today from the end of the last ice age. It is this long duration that allowed diversity to build up there before flowing out into Eurasia.

Neanderthal, witness to the stopover

An independent argument reinforces the existence of this long stopover: our Neanderthal heritage. All non Africans carry in their genome a small fraction of DNA inherited from NeanderthalsNeanderthalsA fossil humanity of Eurasia, robust and cold-adapted, extinct around 40,000 years before present.→, the trace of an interbreedingInterbreedingGenetic mixing between human populations or species; between Neanderthals and Homo sapiens it left 1 to 2% of Neanderthal DNA in non-Africans.→ that occurred after the exit from Africa. This episode of introgressionIntrogressionThe lasting transfer of DNA segments from one population or species into another through repeated interbreeding, detectable in genomes long afterwards.→ can be dated, and it falls precisely within the window when the hub was active.¹

That this Neanderthal signal is shared, in similar proportions, by Europeans, East Asians and Oceanians indicates that the mixing took place before their separation, that is, within the hub population itself. South West Asia then lay within reach of the last Neanderthals, whose range stretched from Europe to the Near EastNear EastA region of western Asia (Levant, Mesopotamia, Anatolia, Iran), cradle of the Neolithic revolution, agriculture, the first cities and writing.→ and as far as the mountains of central Asia. The Persian Plateau and its margins provided the geographical setting for that encounter. The study's first author puts it plainly: this twenty thousand year period sheds light on the interactions with Neanderthal populations and provides crucial clues for understanding the demographic history of our species in Europe, East Asia and Oceania.³

The hub was therefore not a mere waiting room. It is there that part of our biological identity was forged, in prolonged contact with another humanity. The Neanderthal fraction we carry today is, in a sense, the receipt of that stay.

What the hub changes in our story of origins

The position of the Persian Plateau is anything but incidental. Bounded by the Caspian Sea to the north, the Persian Gulf to the south and open toward the Mediterranean to the west, it sits at a crossroads between the Africa our ancestors came from and the Eurasian vastness they were to conquer. That situation made it an ideal launchpad: from this focal area, successive waves could set off westward and eastward, each carrying a share of the diversity accumulated on the spot. The peopling of Eurasia would not have been a continuous, uniform advance, but a series of staggered departures from a single staging ground.

This model reorganises a narrative long centred on the Levant and Arabia, regarded as the first gateways out. It does not erase them, but it shifts the centre of gravity of the initial phase eastward, into these highlands hitherto kept at the margin of the great syntheses. Above all, it offers a coherent framework in which three orders of evidence, previously scattered, slot together: the genetic structure of present day populations, the carrying capacity of the environment reconstructed from climate, and the chronology of Neanderthal admixture. When three independent clues point to the same place, the hypothesis gains in solidity.

It also redraws the map of priorities for research. If the plateau was the staging ground of our species for twenty thousand years, then its caves, terraces and river valleys should hold the archaeological record of that stay, still largely unread. The study effectively hands fieldwork a coordinate and a date range to aim at. Several teams have already signalled their intent to focus on the region, and a new generation of excavations and ancient DNA sampling there could, in the coming years, either confirm the hub or force it to be reconsidered. Either outcome would advance a question that has long resisted answers.

There remains the caution proper to any reconstruction founded on inference. The authors themselves present the Persian Plateau as a key region to explore, not as a closed truth. Ancient genomes from this zone are still lacking, excavations there are rare, and the climate of the period remains imperfectly known. But the strength of the study is to have turned a twenty thousand year void into a precise question, complete with an address. For archaeologists, it is an invitation to dig, in the literal sense, a chapter that has stayed blank in the human adventure. Our ancestors, before becoming Europeans, Asians or Oceanians, would have been, for a long while, people of the plateau.