In 2016, geneticists at Trinity College Dublin sequenced ancient Irish genomes going back four thousand years. When researchers cross-referenced those results with the DNA of thirty million Irish-Americans, they found a gap that should not exist. The descendants of the Famine emigrants now carry a version of Ireland that modern Ireland has partially lost. The Great Famine of 1845 didn’t just kill a million people. It split one Irish gene pool into two, and the older one boarded the boats.
SOURCES:
Cassidy et al. 2016 — Neolithic and Bronze Age migration to Ireland (PNAS)
https://www.pnas.org/doi/full/10.1073/pnas.1518445113
Byrne et al. 2018 — Insular Celtic population structure and genomic footprints of migration (PLOS Genetics)
https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1007152
Gilbert et al. 2017 — The Irish DNA Atlas: Fine-Scale Population Structure within Ireland (Scientific Reports)
https://www.nature.com/articles/s41598-017-17124-4
Moore et al. 2006 — A Y-Chromosome Signature of Hegemony in Gaelic Ireland / Niall of the Nine Hostages (American Journal of Human Genetics)
https://www.cell.com/ajhg/fulltext/S0002-9297(07)62363-5
Britannica — The Great Famine (1845–1852)
https://www.britannica.com/event/Great-Famine-Irish-history
National Museum of Ireland — Irish Emigration to America
https://www.museum.ie/en-IE/Collections-Research/Folklife-Collections/Folklife-Collections-List-(1)/Other/Emigration/Irish-Emigration-to-America
Credit to : Anglo Origins