Homo sapiens decided to explore elsewhere a very long time ago. Out of necessity or for pleasure, it spread across the entire planet. While scientists don't know everything about these ancient migrations, they can trace the first arrivals of our species in the main regions of the globe.
Outings from Africa
The oldest traces of human presence outside of Africa have been found in Georgia. Dated to 1.8 million years ago, they indicate that population movements likely began around 2 million years ago. In Europe, there are other traces of the very first settlements, but they are rare.
For most researchers, African Homo erectus (also called Homo ergaster by some in the scientific community) was the first to migrate. However, some believe that Homo habilis is an equally good candidate and could have been the first migrant.
Whatever species took the step, its members did not decide to leave Africa one fine morning, following a map or an established plan. It was more likely displacements of a few kilometers, and probably back-and-forth movements. This is why scientists speak not of one "Out of Africa" event, but of multiple departures.
THE AFRICAN CRADLE Even if it remains difficult to determine precisely where our history began, there is no doubt that human origins lie in Africa. Fossils discovered at Omo Kibish in present-day Ethiopia, over 200,000 years old, vie for the title of "oldest Homo sapiens" with others dated to 300,000 years old and unearthed at the Jebel Irhoud site in Morocco.
The New Capabilities of the Homo Genus
But what motivated these gradual displacements? Prehistorians favor several hypotheses, notably highlighting strict bipedalism as a triggering factor. While upright posture and walking on two lower limbs exist in various animals, they remain occasional, as in non-human primates, or inefficient, as in Australopithecines.
It was only from Homo habilis and African Homo erectus onwards that we see the appearance of a perfectly enduring biped, much like we are today. This ability could have been a decisive factor in beginning to roam the world.
Another condition considered by researchers, which would have prompted our ancestors to move, is the fact that they gradually transformed from scavengers into hunters. By slowly following herds, they changed territories, likely without realizing it. Moving short distance after short distance, they crossed entire continents – Africa then Asia – over a few generations.
Homo sapiens: An Explorer
Fossil footprints, White Sands site, New MexicoHomo sapiens was the first to occupy all regions of the world. According to population genetics, particularly with the help of molecular dating, all humans living today on our planet descend from a series of "Out of Africa" events that occurred 50,000 to 70,000 years ago. It was therefore Homo sapiens that would spread across all latitudes, altitudes, climates, and environments, proving its ability to adapt to the most diverse ecosystems.
Thus, unlike the African and Asian continents already frequented by other species before ours, Australia (at least around 65,000 years ago), the Americas (at least around 25,000 years ago), or the distant Pacific islands (3,000 years ago) experienced their very first human occupations. This is evidenced by the clusters of clues – tools, bone remains, human remains, etc. – analyzed by prehistorians.
The Underside of Maps: Misleading Representations?
How can migrations be represented on a map, and especially how can the dynamism of these movements be illustrated? Unidirectional arrows do not account for probable back-and-forth movements and seem to indicate intentional progression, always in the same, ever-further direction. This scenario is far from convincing prehistorians.
It is also unlikely that Homo sapiens migrations were marked by precisely localized stages in time and space, such as the moment a population arrived at a location. Scientists believe they more likely resulted from a proliferation of encounters and interbreeding.
The use of arrows to depict major migrations is often misleading, as it leaves no room for the uncertainties and numerous debates surrounding the routes taken.
Map "Ancient Migrations of Homo sapiens, from the Out of Africa to the Colonization of the Pacific Islands" from the catalog of the exhibition Migrations, a Human Odyssey, 2024 © F. Le Goff
Encounters and Interbreeding
While the chronology of migrations remains important, scientists are now working to more precisely establish the contemporaneity between the different human species that inhabited the world, their encounters, and potential interbreeding events between their representatives.
The Difficulty of Attributing Remains to Different Species
Before and during the migrations of Homo sapiens, at least four or five human species were present in the territories it newly frequented. This coexistence proves to be a puzzle for prehistorians! Indeed, how can material discoveries such as lithic tools or meal remnants be attributed to one species or another in the absence of human bones to associate them with? For now, we must rely on hypotheses.
Homo sapiens and Neanderthals Did Indeed Interbreed
The study of genomes has led to significant advances by attesting to episodes of interbreeding, proof of the coexistence of different species. Thus, there are common genes between Homo sapiens and Homo neanderthalensis, as well as between these two and Denisovans, further east in present-day Europe. And likely for which fossils have not yet been found or identified!
Regarding Homo sapiens and Neanderthals, the sequencing of DNA from fossils attributed to them, and whose genomes have been compared with those of current human populations, shows undeniable interbreeding.
However, it remains impossible to specify where their encounter took place: in Europe or on the path leading there, potentially in the Near East, where archaeological traces show it was alternately occupied by both species over a period between 100,000 and 50,000 years ago...
Homo sapiens in Europe
When Homo sapiens arrived in Europe, around 50,000 years ago, it was already inhabited by Homo neanderthalensis. However, it is difficult to determine the exact chronology of the arrival of the former and the extinction of the latter, and thus their potential encounter. This question has fueled debates for decades. Moreover, the analysis of remains attributed to one and the other over successive periods, such as human teeth exhumed from Mandrin Cave (Ardèche), complicates matters by showing that there can be an alternation in site occupation.
Whatever future discoveries may bring, recent advances already allow us to temper the image that clings to Homo sapiens: that of a population exterminator. Because, while we observe that the disappearance of other species systematically occurs shortly after its arrival, nothing proves that it was responsible – let alone intentionally.
Map of the distribution of the Homo genus, between - 50,000 and - 60,000 years, from the catalog of the exhibition Migrations, a Human Odyssey, 2024 © F. Le Goff