Eva-Maria Geigl: “The history of humanity is made up of a succession of migrations”

Whether for reasons prompted by climate change, conflicts, or subsistence, humans have always moved around and intermingled, as the analysis of the genome of bones found at archaeological sites shows. 
Eva-Maria Geigl, co-leader of a palaeogenomics team at the Institut Jacques Monod of the French National Centre for Scientific Research (CNRS)/University of Paris, elaborates.

Interview by Agnès Bardon
UNESCO

What is the role of palaeogenomics?

Palaeogenomics is a discipline that complements archaeology and anthropology. Archaeologists conduct excavations and find bone fragments that they try to place in a given period and culture. The analysis of human remains from excavations can identify the sex of the individual, possibly his or her social status, the diseases that affected him or her – and often even provide indications  on the functioning of a society. 

The work of palaeogeneticists consists of extracting DNA from bones to analyse their genome. This genome is then compared to that of individuals who lived at other times, in other places, or from current populations. In this way, we can reconstruct affiliations – links of kinship, genetic proximity – but also the migrations and interbreeding that occurred over time.

How can genomic information be used to tell the biological history of a population?

Genetic analysis makes it possible to characterize the history of the settlement of a given region, and therefore also the movements of populations and their interbreeding with indigenous communities. Palaeogenomics has shown that 8,500 years ago, farmers of Anatolian or Aegean origin moved to northwestern Europe. Agriculture and animal domestication developed around 12,000 years ago in the Fertile Crescent of the Middle East, in Iran and in Anatolia. About 8,500 years ago, these farmers began to migrate to Europe via a continental route that started in Greece and passed through the Balkans, then Hungary, Austria, and Germany, to arrive in northern France (the Paris Basin).

Another route followed the Mediterranean coast via what is today Croatia, Italy, Sicily, Sardinia, and Corsica, and then on to the south of France and the north-east of the Iberian Peninsula. These phenomena were known thanks to the analysis of remains found during excavations – including fragments of ceramics, flint tools, or bones of domesticated animals such as sheep, which were introduced by these populations of farmers. 

But from the materials available to them, archaeologists could not determine whether only the skills and techniques of the Fertile Crescent farmers had travelled, or whether the inventors of these techniques had physically moved. Through genomic analysis, it was possible to establish that the farmers had mingled with the indigenous hunter-gatherers who had been living in Europe for about 14,500 years, and had partially interbred with these populations.

Does genome-based analysis sometimes shed new light on historical facts?

This happened in 2012, when the remains of a young girl who lived at least 50,000 years ago were discovered in the Denisova Cave in the Altai Mountains of Russia. The genomic analysis of her phalanx demonstrated the existence of a contemporary population of Neanderthals. This population, which inhabited Asia, spread and interbred with the first sapiens from Africa. Until then, palaeoanthropologists did not suspect the existence of this population. 

The migration to Europe of the Yamnaya, nomads from the Pontic steppe north of the Black Sea, is another example. These populations, who had an economy based on cattle-breeding, surged  into central and northern Europe some 5,000 years ago. These steppe nomads, who were mostly men, then interbred with the indigenous farmers of the late Neolithic Period. But as their reproductive success was higher, a significant genomic replacement – called introgression – occurred.  

Even today, in Brittany in the west of France, in Ireland, and in the United Kingdom, eighty per cent to ninety per cent of men carry the Y chromosome of the Yamnaya. This phenomenon was not known to archaeologists because no material traces of the passage of the Yamnaya had been found.

Do we know the causes of these different migrations?

Several causes can be envisaged, but these are only hypotheses. We cannot provide scientific proof. The reasons for these movements could be climatic, but they could also have been demographic. Migrations could be motivated by the necessities related to a group’s subsistence, like hunter-gatherers who followed the migrations of large animals. When the climate changed, humans had to look for other regions they could inhabit. Clashes between populations could also be the cause. Just as we do today, people thousands of years ago probably moved because of climate, for subsistence, or as a result of conflicts. 

Given the analysis of our ancestors’ genomes, can we say that we are all migrants?

Absolutely. To begin with, we are all African, because our ancestors all came from Africa. Homo sapiens evolved in Africa and left the continent in waves. The last wave is that of our direct ancestors. And then, we are all migrants because the history of humanity is made up of a succession of migrations. Since the beginning of time, populations have been moving and intermingling. And this sometimes results in the replacement of indigenous populations, but not always.

We are not sedentary people. We have always had to move and adapt because our environment changed. There are no genetically ‘pure’ populations. This is a good thing, because biologically, we need a mixing of genomes. 

Read more:

Ian Tattersall: The humans we left behind, The UNESCO Courier, December 2000
Yves Coppens talks to Francis Leary, The UNESCO Courier, February 1994
The Teilhard phenomenon, The UNESCO Courier, November 1981 

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