A team of ancient DNA researchers at Trinity have found evidence of matrilocality — a societal system in which married men migrate to live with their female partner’s community — in Iron Age Britain. The study was published in the leading scientific journal Nature this January and has since made international headlines. Trinity News spoke to the team behind the research.
“It is really a privilege to work on such interesting material and uncover new information about people in a time that is just beyond history.”
“We know that there is huge diversity in marriage customs and gender roles across modern day societies, but so far we have only sampled a small fraction of the diversity that has existed throughout human prehistory,” explains Lara Cassidy, Assistant Professor in the Smurfit Institute of Genetics and lead author of the study. “Patrifocal societies might be the norm in many world regions today, but that was perhaps not always the case.” Co-author Dan Bradley, Professor of Population Genetics in the Smurfit Institute of Genetics comments: “It is really a privilege to work on such interesting material and uncover new information about people in a time that is just beyond history. A British Celtic dreamtime.”
In the study, Trinity geneticists sequenced and computationally analysed the genomes of over 50 Iron Age individuals of a tribe buried at a site in Dorset, England, in order to study societal structures and migratory patterns in Celtic times. Among the remarkable discoveries of this study their analysis revealed evidence of a matrilocal society. The team analysed mitochondrial DNA, a type of genetic material passed on only from mothers to children, and found the majority of individuals buried at the site descended from a common female ancestor living a few centuries previous. Analysis also revealed the Y chromosomes, passed only from fathers to sons, of these individuals were diverse, indicating that men migrated into the community. Simulations and modelling, as well as family tree reconstruction, furthered evidence of matrilocality in this society.
“We all grow up with our own cultural norms and beliefs about the past. We have to be careful not to project these norms back onto prehistoric peoples who lived in a very different world;”
Dr Cassidy and the team further analysed a larger data set of Iron Age individuals from across Europe and similarly found evidence for matrilocality across Iron Age Britain, indicating matrilocality was widespread in society in Britain at this time. “To find strong signatures of matrilocality in Iron Age Britain predicts female social and political empowerment,” Dr Cassidy explains. “Importantly, there were already strong suggestions of this from the Roman writings and archaeological record. The problem is that wealthy female graves or accounts of female political leadership have often been dismissed as exceptional cases, rather than a reflection of a society where women wielded a lot of power.” Dr Cassidy continues: “We all grow up with our own cultural norms and beliefs about the past (shaped strongly by almost two millennia of Christianity in Europe). We have to be careful not to project these norms back onto prehistoric peoples who lived in a very different world.”.
“Importantly, we are a teaching lab and like to give 4th year undergraduate students the opportunity to get involved in ongoing research as part of their capstone projects.”
Many members of the ancient DNA lab in Trinity were involved in the generation of data for this study, including academic staff, PhD students, and undergraduate researchers. “We have a wonderful team!” says Dr Cassidy. “Importantly, we are a teaching lab and like to give 4th year undergraduate students the opportunity to get involved in ongoing research as part of their capstone projects.” One of these undergraduate researchers was Beth Heaslip, Human Genetics Class of 2024. “I am so thrilled to have been able to contribute to this amazing study,” says Heaslip, who contributed to work on 7 ancient individuals, identifying a significant second-degree relationship between 2 of them, and contributing to Y chromosome analyses. “Everyone in the ancient DNA lab [was] so wonderful to work with. Lara was an amazing mentor.”
Harry Little, currently a PhD student in the Cassidy lab, shares Heaslip’s sentiments on the value of being involved in research with this group: “It was an absolute privilege to play a small role in this project and to be a part of this amazing team.” Little contributed to wet-laboratory work for the project, extracting DNA from the ancient samples for sequencing and analysis. “Much can be learned from prehistoric civilizations using genetic data,” comments Little. “Studies such as this help to illuminate the societal dynamics and migratory patterns of the past”. In addition to their discoveries regarding matrilocality, the team studied population structure. This genetic analysis uncovered previously undetected Iron Age migration into the south of England, which the team note may have influenced the arrival of Celtic language in Britain.
This is not the first time Dr Cassidy has made headlines with ancient DNA analysis on past societies. In 2020, she led a team in sequencing the genomes of Irish Neolithic individuals, including an adult male buried at Newgrange passage tomb – uncovering a level of inbreeding indicative of a dynastic elite existing in Neolithic Ireland. Such studies by the ancient DNA team at Trinity highlight the wealth of information preserved within genomes, waiting to be uncovered. On the results of this latest study, Dr Cassidy states: “The big take home for me is that the past is really unknown territory in many ways. Ancient DNA is nothing if not surprising!”
