This is fascinating

https://www.bbc.com/news/science-environment-53059527
DNA study reveals Ireland's age of 'god-kings' by Paul Rincon for BBC

A key piece of evidence comes from an adult male buried at the 5,000-year-old Newgrange monument; his DNA revealed that his parents were first-degree relatives, possibly brother and sister....Evidence of incestuous unions like that found at Newgrange are rare in human history; they are taboo for inter-linked biological and cultural reasons. Where they do occur, it is often within royal dynasties that have been granted divine status.
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"It's an extreme of what elites do - marrying within your kin group allows you to keep power within your 'clan',
"But elites also break lots of rules, to separate themselves from the rest of the population... it's a bit chicken and egg: by breaking these rules you probably make yourself seem even more divine."
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The ancient genomic survey also uncovered the earliest diagnosed case of Down's syndrome
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Ireland's Neolithic inhabitants traced their origins to an expansion of people out of Anatolia (modern Turkey) around 6,000-7,000 years ago. This migration transformed Europe's way of life from one focused on hunting to one based on agriculture. Genetically, Ireland's first farmers were most closely related to people living at broadly the same time in Iberia (modern Spain and Portugal).
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DNA predicts that Ireland's hunter-gatherers had a striking combination of dark skin and blue eyes. By contrast, the Anatolian farmers probably had paler skin with brown eyes.