It is less than a decade since scientists developed swift and efficient methods of extracting and analysing ancient DNA from human remains (for which Svante Pääbo was awarded the Nobel Prize for Physiology or Medicine in 2022) and yet scarcely a day goes by without some new breakthrough in our understanding of the past thanks to studies based on ancient genomes. One recent example is the report, published in Nature (https://doi.org/10.1038/s41586-023-06166-6), concerned with the introduction of agriculture to North Africa, settling debates about how and when it occurred. A research team from Sweden, Spain, and Morocco found a remarkable population continuity in north-west Africa until some 7,500 years ago, indicative of a group of local foragers with an ancestry dating back many thousands of years.
Two new genomes were detected at that point, both within a thousand years of each other. The first migrants to introduce a farming lifestyle came from the northern Mediterranean coast. Within a few hundred years, local foragers started to include cultivation in their own lifestyle, though the two groups remained separate, living side by side, for at least another century after that. Around 6,300 years ago, a further new genetic strain appeared in the human remains, brought by migrants from the Levant. All three ancestries then blended during the Late Neolithic.
Dr Rafael Martínez Sánchez from the University of Córdoba, Spain, commented that the genomic data confirms what ceramic decoration was already pointing to: ‘a unidirectional diffusion from the Iberian coast to the Tingitan Peninsula, around 7,500 years ago’. ‘Filling these key chronological gaps in the Maghreb is crucial to understanding how the different subsistence strategies were acquired in this region’, said Dr Youssef Bokbot from the Institut National des Sciences de l’Archéologie et du Patrimoine in Morocco.
Neolithic family DNA
Just how large were the groups of early farmers who took to the seas in search of new lands to farm, accompanied by their breeding stock of domesticated animals and containers full of seed? Analysis of the genomes of 94 individuals from a graveyard in central France provides some insight into the scale of farming communities during the period 4850 to 4500 BC.
The results, also published in Nature (https://doi.org/10.1038/s41586- 023-06350-8) show that two-thirds of the individuals buried at the site called Gurgy ‘les Noisats’, in the Yonne, were closely related. One group comprised 20 females and 44 males, representing seven generations of one family. A second was represented by five generations, made up of seven females and five males. Of the remaining 18 individuals, seven were connected to one of the two groups by one or two degrees of separation, and only 11 were entirely unrelated to either family.
Tooth isotope studies showed that the two groups were ‘patrilocal… with evidence for female exogamy and exchange with genetically close neighbouring groups’. In other words, as other studies have found, men tended to stay in the place of their birth and women married into the community from outside.
The absence of half-siblings and the high number of adult full siblings in the two groups was described as evidence of ‘monogamous reproductive partnering’, low mortality, and stable health conditions. One male was identified as ‘the main ancestor’ of the 52 people of the larger group; only his long bones were found, suggesting that his remains had been buried elsewhere before they were partially transferred and reburied during the early occupation of the necropolis. The female with whom he was buried yielded no genetic results but was perhaps his partner, or another significant representative of the group’s lineage. The son and grandson of the ‘founder’ were found in the largest of the burial pits at the necropolis.
A short-lived cemetery
The fact that the cemetery was used for just a few decades (84 to 112 years) provides new insights into the mobility of farmers during the European Neolithic. The authors speculate that the use of the grave site could correspond to the typical life of a Neolithic Linear Pottery culture longhouse. Experimental archaeology has established that this can vary from between 10 and 30 years but, if the timber posts and thatched roofing materials are regularly renewed, up to 100 years.
Adding to this picture of shifting rather than sedentary farming practice was the absence of adolescents among the first four generations of the first group, which the authors describe as ‘surprising given the expected mortality patterns in archaic populations’. This trend is reversed across the last three generations, with 20 out of 25 individuals being sub-adults. These observations are consistent with a scenario in which an entire group of several generations moved to this new burial site, leaving behind their deceased children at a previous funerary site, but transferring the remains of the ‘ancestor/founder’. The fact that many parents are missing among the later generations suggests that the groups moved on to settle elsewhere, leaving behind those children and adolescents who had passed away.
It remains to be asked whether the necropolis represents a selection of individuals or reflects the whole community. Sites of a similar date elsewhere in France suggest that unrelated individuals were singled out for burial, probably on the basis of economic or social status. Acknowledging that burial practice in Neolithic societies in Europe was very diverse, the authors believe that this cemetery comprises the members of a ‘non-elite community represented over several generations’.
Early farmers probably brought with them seeds of the plants they cultivated, but then began to experiment with the new plants they encountered in the wild. In Africa, these included Digitaria exilis the grass-like plant that is called fonio, acha, findi, or fundi in different parts of west Africa. Environmental evidence shows that fonio has been cultivated for 5,000 years, but it fell out of favour because it was seen as inferior to ‘white-man’s food’, the rice and imported grains introduced by colonial powers.
The merits of fonio are now being rediscovered by chefs, brewers, and food manufacturers because this ancient grain grows quickly in poor soils; needs little of the irrigation, pesticides, or fertilisers demanded by barley, wheat, or rice; and outranks other grains in protein, iron, fibre, and amino acid content. Senegalese-born chef Pierre Thiam is carving out a niche as a champion of fonio, which he says is an African superfood, easy to cook, versatile, and flavoursome.
By creating an international demand for fonio, Thiam aims to help the environment, give African farmers a sustainable income, and help Black people feel that their food is part of culinary history and culture. Consumers in Europe and America are most likely to encounter fonio in beer: Garrett Oliver, of the Brooklyn Brewery, says it ‘creates beautiful flavours – there are floral and fruity notes that remind me of lychee or Gewürztraminer’.
Descendants of the enslaved
A third recent DNA-based paper – this time published in Science (www.science.org/doi/10.1126/science.ade4995) – raises the possibility that many more people could find their enslaved ancestors through genetic analysis. Records relating to enslaved people tend to be sparse or non-existent, complicating efforts to trace their family connections, but researchers have now analysed DNA from more than two dozen enslaved people who were buried at the Catoctin Furnace, a historic iron forge in Maryland, excavated and conserved by the Catoctin Furnace Historical Society. The results were then used to search for matching DNA in the database of the San Francisco-based genomics company 23andMe (23 being the number of chromosomes in human cells). The company has records of 9.3m customers who have given permission for their data to be used in research.
The analysis found 500 people with a close connection to Catoctin Furnace ancestry across the United States, but with especially high levels concentrated in Maryland, suggesting that former furnace workers stayed put. Another cluster with high levels of Catoctin ancestry was found in the southern United States, perhaps indicating that some enslaved people were sold and moved there.
The research was based on anonymous data: none of the people with Catoctin ancestry have been informed, and the research has ethical implications, but Henry Louis Gates Jr, Director of the Hutchins Center for African & African American Research at Harvard University, says that such issues are worth resolving: ‘each time we are able to find an enslaved ancestor, we are defeating the purpose of slavery. The purpose of slavery was to rob us of that information’, he says, adding that ‘I have never met an African American who did not want to know as much as possible about the lives and times of their ancestors who suffered in the bowels of slavery’.