While Anatolian farmers quickly replaced most of the population of Europe and North Africa, the foragers of the eastern Maghreb persisted in their ways for thousands of years
The Neolithic, which began around 12,000 years ago in the Fertile Crescent, was arguably the first great revolution in the human past. It marked a shift away from the hunter-gathering lifestyle that prehistoric humans had kept for hundreds of thousands of years and the start of farming, animal domestication and sedentary living.
Around 7,500 years ago, it also brought about a huge population change, as Anatolian farmers migrated from the cradle of agriculture in southwest Asia across Europe, North Africa and the Mediterranean, spreading their genes along with their way of life. This rapid and massive expansion subsumed most of the existing local populations, meaning that those early Anatolian farmers now represent the single largest ancestral component in the genome of modern-day Europeans.
However, inquisitive minds want to know: Did this happen everywhere and at the same time? A new ancient DNA study, focusing on the Neolithic inhabitants of North Africa shows that part of this region displayed remarkable resistance, both culturally and genetically, to the sea change that occurred during the Neolithic around the rest of the Mediterranean and beyond.
The study published Wednesday in Nature reconstructed the genome of nine individuals who lived between 15,000 and 6,000 years ago in the eastern Maghreb, the area that includes modern-day Algeria and Tunisia. These people could trace only a fraction of their ancestry, less than 20 percent, to early farmers, and largely preserved the genetic lineage of their hunter-gatherer ancestors for thousands of years, a team of geneticist and archaeologists reports.
The finding is in contrast with previously published research from the western Maghreb, which is in modern-day Morocco. There the Neolithic population was in fact deeply impacted by the migration of early farmers from Iberia, who contributed around 80 percent to the local gene pool.
The study sheds new light on the process of “Neolithization” and in particular on the question of whether the spread of farming occurred mainly through population movement or through mere contact and cultural exchange.
We do know of pockets in which the genome and lifestyle of European hunter-gatherers held out on the backdrop of the Neolithic revolution for a long time, says Prof. David Reich, a leading ancient DNA expert at Harvard University. But these were mostly in northern Europe in smaller areas unsuitable for farming, whereas the eastern Maghreb was a large region mostly suitable for farming, with a climate not too dissimilar from the Levantine one in which agriculture first developed, he notes.
The reason for the genetic resilience of the people in the eastern Maghreb is not clear. But this phenomenon is mirrored in the archaeological data, which shows that crop farming did not take root in the region until the beginning first millennium B.C.E., around 3,000 years ago, says Dr. Giulio Lucarini, an archaeologist with Italy’s National Research Council. That is around 7,000 years later than in the Fertile Crescent and about 5,000 years after farming began to appear in North Africa.
“It’s not often that there is such a clear match between genetic and archaeological data,” Lucarini says. “When I first read the email with the results from the genetic testing I jumped off my chair, because it told the same story of this very different Neolithic that archaeologists have been trying to tell for years.”
The nine genetic samples used in the study came from burials in three Neolithic sites in Tunisia and one in Algeria. The sites are a mix of rock shelters and temporary villages that were used by the local hunter-gatherers, Lucarini says.
It could be noted that nine genomes is not exactly a very large sample, and there is indeed a paucity of ancient genetic material from the region, Reich says. However, as Bob Dylan sang, we all “contain multitudes,” and the genome of nine people can still be used to tell broader stories, because it includes genetic information on a person’s grandparents, great-grandparents and distant ancestors, Reich notes.
The genetic data says that to the west, in Morocco, and further east, in Egypt, the first farmers were settling down and largely absorbing the local hunter-gatherer populations, there was very limited gene flow into the east Maghreb. By 7,000 years ago there were some contributions from European farmers coming in from Iberia and Morocco, and by 6,800 a small percentage of Levantine ancestry began to appear, the researchers report.
This may be correlated to one Neolithic innovation that did spread to the eastern Maghreb around this time: animal husbandry, which may have been brought from the Levant, Lucarini says.
For the next millennia, the people of the eastern Maghreb continued to be highly mobile hunter-gatherers, simply adding on to their traditional economies the shepherding of cattle, goats and sheep, he explains.
“There seems to be a rejection of a sedentary lifestyle,” Lucarini says. “They just weren’t interested.”
And it’s not that the hunter-gathering cultures of Algeria and Tunisia were particularly primitive or insular, the researchers note. The opposite seems to be the case.
One of the most striking findings of the genetic study is that some of the sampled individuals could trace small parts of their ancestry to European hunter-gatherers. This means that around 8,500 years ago, well before the Anatolian farmers arrived, hunter-gatherers from across the Mediterranean were very much in close contact with each other, the researchers say.
The archaeological record suggests that these contacts may have taken place through seafaring across the Strait of Sicily, which separates Tunisia and Italy. For example, at Hergla, a Tunisian coastal site where some of the human remains analyzed in the study were found, archaeologists also discovered obsidian from Pantelleria, a volcanic island between Tunisia and Sicily, Lucarini notes.
Besides, we know that humans, or even evolutionary predecessors of Homo sapiens may have been sailing the Mediterranean for hundreds of thousands of years. Given that boats would have been made with perishable wood, evidence of prehistoric navigation is hard to come by, but not unheard of.
While we don’t have ships from the Neolithic in Tunisia, archaeologists have found 7,000-year-old seaworthy canoes at the bottom of Lake Bracciano in central Italy, showing that seafaring was indeed possible at the time. In another suggestion of interconnectedness, the hunter-gatherers of the eastern Maghreb also started using pottery around 8,000 years ago – another innovation closely associated with the Neolithic revolution – with styles reminiscent of vessels that were being made in other areas of the Mediterranean, the researchers note.
“So the eastern Maghreb is not an isolated place that doesn’t have contact with the outside,” Reich says. “And these hunter gatherers are no slouches, they can get across the Mediterranean, they can trade stuff. It’s an incredible group of people.”
So why did the region resist sedentarization and crop farming so strongly? We can’t be sure, but perhaps their foraging economy was so strong that the communities in the eastern Maghreb didn’t feel the need to settle down and raise crops, Reich says.
Meanwhile, hunter-gatherer populations in Europe may have been weakened by an extended period of cooling that hit the world about 8,200 years ago. This climatic event, which may have affected North Africa less, may help explain why the hunter-gatherers of Europe were so quickly overtaken by the Anatolian newcomers.
Lucarini also suggests another factor may have played a role in the eastern Maghreb’s genetic and cultural resilience. Both Morocco and Egypt have large river systems and it was along these waterways that farming communities in these regions first formed in the Neolithic. While their coastal strips are not arid or infertile, Tunisia and Algeria lack such large rivers, which could have made farming a more dangerous proposition.
“They had this very diversified economy of hunting game, foraging for wild plants, fishing and shepherding. If one resource faltered they could easily supplement it with another,” Lucarini concludes. “Settling down to farm a specific plot of land is a big investment and can make your survival dependant on the success of the crops. And without a stable supply of water nearby, why would they risk it?”
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