MCT researchers shed light on the ancestry of the Irish Travellers from the perspective of DNA

Edmund Gilbert reports

A new study, led by Prof. Gianpiero Cavalleri at MCT and Prof. Jim Wilson at the University of Edinburgh, has examined the population history of the Irish Travellers and has confirmed that the Irish Travellers share a common Irish origin with the settled Irish population. The work has also for the first time estimated the date which this divergence occurred.

A roadside camp in County Mayo 1972. Courtesy of George Gmelch

The Irish Travellers are a small nomadic population, making up about 0.6% of the total population on the island of Ireland, or between 29,000 and 40,000 individuals. Within the population cousin marriages (consanguineous marriages) are common, and the population is socially isolated from the surrounding settled Irish population.
The researchers, who also include MCT PhD student Edmund Gilbert, Shai Carmi of the Hebrew University of Jerusalem, and Sean Ennis of University College Dublin, used SNP-array based genotype data to compare the population genetics of the Irish Travellers to neighbouring Irish and British populations, as well as world-wide groups and European Roma Gypsies.
The study found that although the Irish Travellers were genetic closest to the settled Irish population, they showed significant differences. The study also confirmed the lack of recent shared genetic ancestry between the Irish Travellers and Roma Gypsies. The Irish Travellers, therefore, represent a subset of Irish genetic diversity, and the significant differences can be attributed to genetic drift, brought on by hundreds of years of genetic isolation and a decreasing population size. The analysis showed Irish Travellers also exhibit within-population sub-structure with four apparently distinct groups emerging, and interestingly these groups mirror different forms of the Shelta language and sociological groups within the Irish Travellers.

Galway John Ward making tinware and Galway 1971. Courtesy of George Gmelch

The dating of the origin of the Irish Travellers is of considerable interest, but this is a distinct date from the genetic origins of each population. This study has estimated a time of genetic divergence of the Irish Travellers and the settled Irish population using genomic tracts of shared identity. This method estimated the divergence to about 12 generations (360 years) ago, which is far older than common belief that the Irish Traveller population arose from the time of the Great Famine. The size of the dataset limited the authors to exploring the relatively simple model of one divergence event, future work is required to expand the study to explore more complex demographic models. The Irish Traveller population was shown to have high proportions of the genome where both maternal and paternal copies are identical, at similar levels to other consanguineous populations around the world.
The research was also welcomed by author and Traveller activist, Michael McDonagh said, “As a Traveller who has spoken on the history and identity of Irish Travellers to many groups ranging from children to academics, you sometimes rely on anecdotal information in trying to put across a serious message about Irish Traveller history. I am delighted that now we have qualified evidence that substantiates the argument I have made for many years, which is that Travellers did not descend from the Famine in Ireland. This research allows us to bring Irish Traveller history back many and gives us a factual identity.”

Using genotype data to infer population structure and history

MCT Research Talk – 12th December

The Human Genetic Variation Research Group 

The Monday 12th December MCT Seminar Series will feature presentations from Amy Cole and Edmund Gilbert, of the Human Genetic Variation Research Group at RCSI. Led by Prof. Gianpiero Cavalleri, this research group studies large genetic datasets to investigate population structure, natural selection and the genetic basis of human disease.

Andean native in a small village on the outskirts of Cuzco

Amy Cole’s research focuses on identifying adaptive genetic variants in high altitude populations.  There are more than 140 million people living at high altitude who are exposed to two primary environmental extremes; hypobaric hypoxia and cold. At altitudes >2500 m individuals have between 11-14% effective oxygen availability, instead of the 21% available at sea level. Previous studies have identified genetic signals of selection across the genome, which have facilitated an adaptive phenotype for survival in this hypoxic environment.  Studying these indigenous high altitude populations will enable us to shed light on genes and molecular mechanisms involved in the response to hypoxia. This insight can help shed light on a number of illnesses associated with hypoxic states in low altitude populations, such as pneumonia, chronic obstructive pulmonary disease, asthma and cancer.

Research group en route to Cerro de Pasco

Today Amy presented research on a whole genome sequencing project on native high altitude Quechua individuals, recruited from the city of Cerro de Pasco, Peru, during a field trip in 2015.  Amy recently completed a three-month lab placement at MD Anderson Cancer Center with Professor Chad Huff’s research group. Here Amy performed a number of computational analyses to identify regions of the genome that are under selection in this cohort.

Edmund Gilbert’s research involves investigating the genetic structure and diversity found within the Irish. As an island population on the west of Europe, the Irish population is, from the genetic perspective, relatively homogenous compared to populations of the European mainland. As a results of this elevated homogeneity, the Irish population is well suited to studies of genetic disease. Such studies have recently shifted focus towards rare variants, which are more geographically stratified than more common variants. Therefore understanding the population structure within Ireland is key for the optimal design of genetic disease causing rare variant identification within the Irish.

Today Edmund will be presenting research investigating the extent of fine-scale population structure found within Ireland. He has been using SNP-array genotype data from the genetic ancestry DNA cohort called the “Irish DNA Atlas”. The Atlas is a cohort of individuals with Irish ancestry from three generations ago who have all eight of their great-grandparents born within 50 km. Edmund will be presenting analysis based on the suite of software known as fineStructure; investigating both fine-scale structure as well as the genetic ancestry of this structure.

Amy Cole, Edmund Gilbert, Gianpiero Cavalleri