Ancient DNA from Sardinia reveals 6,000years of genetic history24 February 2020, by Matt Wood

The s'Orcu 'e Tueri nuraghi, one of many distinctiveSardinian Bronze Age stone towers dating to the mid- tolate 2nd millennium BC, at a site including in the study.Credit: Gruppo Grotte Ogliastra

A new study of the genetic history of Sardinia, aMediterranean island off the western coast of Italy,tells how genetic ancestry on the island wasrelatively stable through the end of the BronzeAge, even as mainland Europe saw new ancestriesarrive. The study further details how the island'sgenetic ancestry became more diverse andinterconnected with the Mediterranean starting inthe Iron Age, as Phoenician, Punic, and eventuallyRoman peoples began arriving to the island.

The research, published in Nature Communications,analyzed genome-wide DNA data for 70 individualsfrom more than 20 Sardinian archaeological sitesspanning roughly 6,000 years from the MiddleNeolithic through the Medieval period. No previousstudy has used genome-wide DNA extracted fromancient remains to look at the population history ofSardinia.

"Geneticists have been studying the people ofSardinia for a long time, but we haven't knownmuch about their past," said the senior author JohnNovembre, Ph.D., a leading computational biologistat the Univeristy of Chicago who studies geneticdiversity in natural populations. "There have beenclues that Sardinia has a particularly interestinggenetic history, and understanding this historycould also have relevance to larger questions aboutthe peopling of the Mediterranean."

An interdisciplinary team

The people of Sardinia have long been studied bygeneticists to understand human health. The islandhas one of the highest rates of people who live to100 years or more, and its people have higher thanaverage rates of autoimmune diseases anddisorders such as beta-thalassemia and G6PDdeficiency. Many villages in Sardinia also have highlevels of relatedness, which makes uncovering thegenetics of traits simpler. Across the island, thefrequencies of genetic variants often differ frommainland Europe. These factors have madeSardinia a useful place for geneticists like seniorauthor Francesco Cucca from the Università diSassari in Italy to uncover genetic variants that maybe linked to disease and aging.

"Contemporary Sardinians represent a reservoir forsome variants that are currently very rare incontinental Europe," Cucca said. "These geneticvariants are tools we can use to dissect the functionof genes and the mechanisms that are at the basisof genetic diseases."

1 / 4

Sardinia also has a unique archaeological,linguistic, and cultural heritage, and has been partof Mediterranean trade networks since the Neolithicage. How much the population's genetic ancestryhas changed through these times, however, hasbeen unknown.

To generate a new perspective on the genetichistory of Sardinia, long-term collaborators Cuccaand Novembre brought together an interdisciplinarygroup with geneticists, archaeologists, and ancientDNA experts. A team led by Johannes Krause atthe Max Planck Institute for the Science of HumanHistory and the University of Tübingen in Germanyhelped coordinate the sampling and carried outDNA sequencing and authentication. Teams led byNovembre and Cucca then analyzed the data andshared the results with the whole group for aninterdisciplinary interpretation.

"We were thrilled to be able to generate such adataset spanning six thousand years because theretrieval of ancient DNA from skeletal remains fromSardinia is very challenging," said Cosimo Posth,an archaeogeneticist at the Max Planck Instituteand co-first author of the study.

The town of Seulo, Sardinia, around which there areseveral cave archaeological sites that have beenexcavated by study co-authors Maria Giuseppina Gradoli,Robin Skeates, and Jessica Becket and from whichsamples were collected for the study. Credit: JohnNovembre

Periods of stability and change

Sampling DNA from ancient remains allowsscientists to get a snapshot of people living at aspecific time and place, instead of using modernDNA and inferring the past based on assumptionsand mathematical models. When the teamcompared the DNA of 70 ancient individualscollected from Sardinia to the DNA of other ancientand modern individuals, they uncovered two majorpatterns.

First, they saw that Sardinian individuals in theMiddle Neolithic period (4100-3500 BCE) wereclosely related to people from mainland Europe ofthe time. Genetic ancestry then remained relativelystable on the island through at least the end of the"Nuragic" period (~900 BCE). This pattern differsfrom other regions of mainland Europe whichexperienced new ancestries entering from peoplemoving across the continent in the Bronze Age.

The results also show the development ofSardinia's distinctive nuraghe stone towers andculture (after which the Nuragic period is named)did not coincide with any detectable, new geneticancestry arriving to the island.

"We found striking stability in ancestry from theMiddle Neolithic through the end of the Nuragicperiod in Sardinia," said Joe Marcus, a Ph.D.student in the Department of Human Genetics atUChicago and a co-first author on the paper.

Second, the team found evidence of the arrival ofdifferent populations across the Mediterranean, firstwith Phoenicians originating from the Levant(modern-day Lebanon) and Punics, whose culturecentered in Carthage (modern-day Tunisia). Then,new ancestry continued to appear during theRoman period and further in the Medieval period,as Sardinia became historically influenced bymigration of people from modern-day Italy andSpain.

"We observed clear signals of dynamic periods ofcontact linking the island to the rest of theMediterranean, appearing first in individuals fromtwo Phoenician and Punic sites as early as 500BCE, and then in individuals from the Roman and

2 / 4

Medieval periods," said Harald Ringbauer, Ph.D., apostdoctoral researcher involved in thecomputational data analysis at UChicago and a co-first author on the paper.

The group's results help explain similarities withDNA from mainland European individuals of theNeolithic and Copper Age, such as "Ötzi theIceman," an almost perfectly preserved, 5,300-year-old human discovered in alpine ice in northern Italyin 1991. Specifically, among modern Europeans,Ötzi's DNA is most similar to modern-daySardinians. The new study supports the theory thatthis similarity remains because Sardinia had lessturnover of genetic ancestry over time thanmainland Europe, which experienced large-scalemigrations in the Bronze Age.

Insights from the past, implications for thepresent

Besides providing new insight into mysteries of thepast, studying ancient DNA also has implicationsfor the well-being of present-day humans. Thismodel of Sardinia's populationhistory—establishment followed by relative isolationand then the arrival of new sources ofdiversity—provides a new framework forunderstanding how genetic variants with healthimplications became more frequent on the island.

"For future studies, we want to look more preciselyat mutations that we think are involved in disease tosee in which period they changed in frequency andhow quickly they changed," Novembre said. "Thatwill help us understand the processes acting onthese diseases, and in turn gain a richer view thatmay yield insights for human health."

The study, "Genetic history from the MiddleNeolithic to present on the Mediterranean island ofSardinia," was published February 24, 2020 in Nature Communications. An independent study in Nature Ecology and Evolution also publishedFebruary 24, 2020 comes to similar conclusionsusing different samples.

More information: Joseph H. Marcus et al,Genetic history from the Middle Neolithic to presenton the Mediterranean island of Sardinia, Nature

Communications (2020). DOI:10.1038/s41467-020-14523-6

Daniel M. Fernandes et al. The spread of steppeand Iranian-related ancestry in the islands of thewestern Mediterranean, Nature Ecology &Evolution (2020). DOI: 10.1038/s41559-020-1102-0

Provided by University of Chicago

3 / 4

APA citation: Ancient DNA from Sardinia reveals 6,000 years of genetic history (2020, February 24)retrieved 3 January 2022 from https://phys.org/news/2020-02-ancient-dna-sardinia-reveals-years.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, nopart may be reproduced without the written permission. The content is provided for information purposes only.

Powered by TCPDF (www.tcpdf.org)

4 / 4