Prehistoric rock art
Understanding ancient civilisations
MIGRATIONS
Our species (Homo sapiens) is the only one that is present on all continents. Its final expansion, which started 70,000 years ago, is one of the many migrations by the Homo genus. Recreating these journeys is complex and requires a multidisciplinary approach at the crossroads of three fields of research: archaeology, which examines the traces left by hominids (tools, fossils), paleo-genetics, which recreates the relationship between the human species and geochronology which, using radio isotopic dating methods, positions these data in terms of time.
The researchers of the Climate and Environmental Sciences Laboratory (LSCE) are among the world’s leading specialists in these methods, which include radiocarbon (14C), uranium-thorium (238U/230Th), potassium-argon (40K/40Ar) and argon-argon (40Ar/39Ar) as well as thermoluminescence [see “Dating methods”]. They helped to reconstruct migration pathways which are illustrated below with three maps.
Very few clues remain about the first migration routes. There are few fossils and mainly some stone tools or traces left by them on bones. After an initial expansion in Africa between 2.4 and 2.1 million years [1][1] Sahnouni et al., 2018 Science 362, 1297-1301, the ancient hominids (e.g. Homo erectus) arrived in Eurasia between 2.1 and 1.8 million years [2][2] Messager et al., 2011 Quat. Sci. Rev. 30, 3099-3108; Zhou et al., 2018 Nature 559, 608-612.. They colonised Sangiran in Indonesia about 1.5 to 1.6 million years ago [3][3] Larick et al., 2001 Proc. Natl. Acad. Sci. U. S. A. 98, 4866–4871.. Traces of the first migrations to Europe date from 1.2 to 1.4 million years [4][4] Toro Moyano et al., 2013 J.of Hum. Evol. 65, 1-9.; Arzarello et al., 2009 Naturwissenschaften 94, 107–112. and 1.1 million years in France [5][5] Despriée et al., 2011 Quat. Sci. Rev. 30, 1474-1485.. Several other waves of different species of hominids reached Europe and Asia more recently, between 1 million and 600,000 years ago.
Some of these ancient populations that moved out of Africa and gave birth to Homo neandertalensis in Europe, Homo denisovensis in Asia, but also island forms of small humans, such as the “Hobbits”, Homo floresiensis and, more recently, Homo luzonensis [6][6] Détroit et al., 2019 Nature 568, 181-185 discovered on the islands of Florès (Indonesia) and Luzon (Philippines) respectively (Fig. 3). The discoveries made on these islands prove that, as early as 700,000 years ago, men were able to cross open seas [7][7] Van den Bergh et al., 2016 Nature 534, 245-248 ; Ingicco et al., 20181 Nature 557, 233-237. and that ancient migration via the Mediterranean was therefore possible (Fig. 1). Among these regional species resulting from ancient migrations, only Homo neandertalensis returned in the direction of the Levant and central Asia, where he met another species, this one African, Homo sapiens (Fig. 2 and 3). This meeting left a trace (1 to 2%) in the genome of present-day Europeans [8][8] Prüfer et al., 2014 Nature 505, 43-49.. This hybridisation took place several times and in several locations, because 20 to 30% of Neanderthal genes can be found in today’s population [9][9] Vernot et Akey, 2014 Science 343, 1017-1021.. In Asia, 90,000 years ago, Neanderthals also mated with Homo denisovensis [10][10] Slon et al., 2018 Nature 561, 113-116.
Our species, Homo sapiens, appeared 300,000 years ago in Africa [11][11] Hublin et al., 2017 Nature 546, 289–292. Recent migrations are precisely dated using 14C method, but the rapid migration to Asia and Sahul, remains an enigma, because dating methods are not precise enough.
Once again, the exodus from Africa was in waves. The first traces found date from 180,000 and 120,000 years ago in Israel and the Arab peninsula [12][12] Armitage et al., 2011 Science, 331, 453-456. ; Hershkovitz et al., 20181 Science 359, 456-459. and from 90 to 110,000 years ago in Asia [13][13] Michel et al., 20161 J.of Hum. Evol. 101, 101-104.. The world’s current population is the result of a more recent migration, which began 70 to 65,000 years. Homo sapiens reached Asia and as far as Sahul in a few thousand years. He met Homo denisovensis in Asia, with their descendants currently living in Tibet, South-East Asia and Papua [14][14] Browning et al., 2018 Cell 173, 53-61. [15][15] Chen et al., 2018 Nature In press, https://doi.org/10.1038/s41586‐019‐1139‐x.. Homo sapiens' adaptation to high altitude could be inherited from the Denisovians who lived more than 160,000 years ago on the Tibetan plateau (Baishiya site, Fig. 2) [15][15] Chen et al., 2018 Nature In press, https://doi.org/10.1038/s41586‐019‐1139‐x.. At about 45 to 40,000 years, Homo sapiens arrived in Europe. At least 24,000 years, maybe even before 28,000 years ago [16][16] Vialou et al., 20171 Antiquity 91, 865-888., the first groups crossed Beringia and reached America [17][17] Bourgeon et al., 2018 PloS ONE 12, (1) :e0169486.doi :10.1371/journal.pone.0169486.. A new wave of migration, which started 18,000 years ago, reached the south of the continent 14,000 years ago [18][18] Politis et al., 2016 PLoS ONE 11(9): e0162870 doi:10.1371/journal.pone.0162870., thus completing the peopling of all the continents.
Glossary
The Hobbits: small hominids (average 1.1m). Term taken from the novels of J.R.R Tolkien.
Sahul: name of the continental plateau, the emerged parts of which are today Australia, Tasmania and New Guinea.
Beringia: land bridge which existed at various times between Alaska and Western Siberia. Today, a narrow stretch of sea called the Bering Straits separates North America and Asia.
Prehistoric rock art
Pigments and metals
New applications