Jean Manco

“Adults who could digest raw milk had an excellent source of food on the hoof. Cattle could go on turning grass into milk for years before they were slaughtered for beef. It has been proposed that lactase persistence was the genetic edge that allowed the dairy pastoralist Indo-Europeans to spread. Dairy farming produces five times as many calories per acre as raising cattle for slaughter.61 The protein and calcium of milk certainly build bones. Prehistoric dairy farmers tended to be taller than other farmers.62”
― Jean Manco, Ancestral Journeys: The Peopling of Europe from the First Venturers to the Vikings

“Its offshoot I2a2a1a1a1a (S7753) includes men of several surnames of Irish Gaelic origin, such as McGuinness, Callahan, McConville and McManus, indicating that S7753 arrived in Ireland before the development of surnames. The estimated date of the haplogroup is around AD 500, which makes a neat fit to the earliest reference to the Cruithin in AD 552 (see p. 169).41 84 Tree of Y-DNA haplogroup I2a2a1a1 (M284).”
― Jean Manco, Blood of the Celts: The New Ancestral Story