But a single Neolithic individual in the west of Ireland was found to have hunter-gatherer genes in his recent family tree, suggesting the indigenous peoples were assimilated rather than exterminated, Cassidy said.
The researchers also found genetic evidence of the earliest-known case of Down Syndrome, in a male infant buried in the Poulnabrone tomb in Ireland's County Clare and dating from more than 5,500 years ago.
Analysis of certain chemical isotopes shows that the infant was fed breast milk, and he was given a prestige tomb burial — probably a signifier of elite descent, Cassidy said.
NOTE: Brú na Bóinne, which means the 'palace' or the 'mansion' of the Boyne, refers to the area within the bend of the River Boyne which contains one of the world's most important prehistoric landscapes.