Famine, tea, and bread in Ireland: C282Y and modern human microevolution

Abstract

The HFE gene variant allele C282Y connected with hereditary hemochromatosis occurs at a frequency of about 10%–11% in Ireland, the highest known frequency in the modern global population. In this synthesis, we draw together an interdisciplinary literature to offer an agriculturally‐grounded, biocultural example of modern human adaptation and microevolution that addresses Ireland's comparatively high C282Y frequency. We argue that changing subsistence‐, diet‐, and nutrition‐related stressors framed under colonial governance played a role shaping the biology of Ireland's population historically, maintaining the C282Y variant. A population accustomed to challenges of poverty and difficult living conditions, the Irish fell under the influence of massive ecological stress with the fungus (Phytophthora infestans), the failed potato crops, and the Great Famine of 1845–52. From there, in the post‐Famine era, diet and nutrition altered further as the potato was exchanged for gluten‐rich wheaten bread and stewed black tea. With risks for iron deficiency anemia heightened by the cultural construction of diet and niche, an adaptive iron‐conserving advantage continued to be offered by the C282Y allele, influencing survival into the post‐Famine era. More recently, however, C282Y has been reframed as a potential risk in the context of contemporary, iron fortified diets.